The Rising Damp Myth

By: admin | Posted on: February 12, 2021

A REVIEW OF JEFF HOWELL’S BOOK ‘THE RISING DAMP MYTH’

RISING DAMP

From ‘The Rising Damp Myth’ by Jeff Howell

“For the fact that rising damp is a mythical building defect, which only came to widespread prominence in the 1960s—-“

“The rising damp myth has become so powerful, and so deeply ingrained in the psyche of the construction professions, that you question it is to invite denial and even ridicule.”

Some recent quotes:

Architects Journal 2009:

“Rising damp is as rare as a rocking horse s**t!!”

Elaine Blackett-Ord, Blackett_Ord Conservation Architects, Cumbria: also chair of the Register of Architects Accredited in Building Conservation

Architects Journal 2009:

“Stephen Boniface, former chairman of the construction arm of the Royal Institution of Chartered Surveyors (RICS), has told the institute’s 40,000 members that ‘true rising damp’ is a myth and chemically injected damp-proof courses (DPC) are “complete waste of money”.

THE ORIGIN OF THE TERM ‘RISING DAMP’

In the book ‘The rising Damp Myth’ the author states,

“The earliest use of the phrase “rising damp” that I could find in official literature was from 1951 —“

However:-

Transactions of the Royal Institute of British Architects 1862-3

“The dry rot which had once required all the timbers to be removed, and was now again destroying them, will be prevented by the circulation of air, and the house will be as free from rising damp as if upon a gravel soil”

(from a paper on damp-proof courses and dampness in buildings)

rising damp 1862
RISING DAMP 1841
RISING DAMP 1872

RISING DAMP

We could define rising damp as:

The vertical movement of water up through masonry, the water originating from ground water. The water rises up through a series of interconnecting pores by a process called ‘capillarity’ – broadly, porous masonry acts like a ‘wick’.

Note: The rise of liquids from roots to leaves in plants is a process knows as ‘cohesion’ (‘transpiration pull’), not simple capillarity, and involves hydrogen bonding of water.

Rise of liquids in plants is NOT simple capillarity as indicated in the book ‘The Rising Damp Myth’!!

(Also his calculations and decimal points for heights of rise are wrong!)

RISING DAMP

Ground water contains a proportion of soluble materials, both organic and inorganic.

Of the dissolved soluble inorganic materials the most prevalent are:

Chlorides

Nitrates

Sulphates

Most building materials are, for practical purposes, free of chloride and nitrate (<0.01% – such levels are of no consequence). However, sulphates can be present naturally at much higher levels.

So if soluble chloride and nitrate are present at readily identifiable levels they must have originated from some source.

RISING DAMP AND HYGROSCOPIC SALTS
RISING DAMP AND HYGROSCOPIC SALTS
RISING DAMP AND HYGROSCOPIC SALTS
RISING DAMP AND HYGROSCOPIC SALTS
RISING DAMP AND HYGROSCOPIC SALTS
FLOODING BURST PIPE

HEIGHT OF RISE

One major factor in rise is pore diameter. Pore size in bricks/mortar can be as small as 0.001mm radius

Average size is around 0.01mm radius

A pore size of 0.01,, radius gives a theoretical height rise or around 1.5m!

Thus rising damp can rise WELL in excess of 1m, the height frequently claimed to be the maximum!

RISING DAMP

It must be fully appreciated that no walls without a physical damp-proof course will be subject to rising damp!

Therefore taking an old wall and immersing it in water will not prove or disprove the existing of rising damp as implied in ‘The rising damp myth’!

Similarly, structures built into water may not have rising damp; again, no ‘proof’ that rising damp doesn’t exist as some suggest.

LABORATORY SIMULATION IF RISING DAMP

Architect Journal 2009:

“Jeff Howell, a qualified bricklayer and author of ‘The Rising Damp Myth’ (2008) said trails in the laboratory [1993-96] confirm the falsehood [RISING DAMP]. If you build a brick pillar and stand it in a tray of water, the bricks in the water will get wet, but the water doesn’t rise by capillary action, ‘ said Howell. ‘Cement-based and most lime-based mortars will not allow water to go through.’”

BUT Letter from Jeff Howell to one sponsor in 1994:

“ In the foreground are two pillars of ibstock Red Leicester facing bricks (14% porosity) which are nicely wet up to five courses, and starting to show a pattern of efflorescence at the evaporative surface. Behind then two pillars of LBC Flettons, not so damp but, interestingly, the mortar is visibly damp up to the sixth course.”

— and Jeff Howell to sponsor in 1995:

“This wall had been standing in water for eight months, and had some hygroscopic salt contamination. It had rising damp which was visible up to a level of approximately 500 mm (six courses). It therefore represented a typical rising damp complex.”

(If it was “typical”: then, by definition, it was “characteristic/representative” of a commonly observed phenomenon, ie, it is well recorded and therefore he must have GOOD experience of it!)

On Howell’s quote:

‘Cement-based and most lime-based mortars will not allow water to go through.’

This is partly true for fresh, uncarbonated materials – but not for 80+year old materials – their permeability changes: it also depends of the strength of the mortar mix. (However, note that recently applied cement renders following dpc installation can fail in a short time, ie, let water and salts through!! Old and moderately recently lime mortars are distinctly permeable)

Cement/lime mixes in the laboratory cannot readily be aged to replicate the physical properties of the old materials – therefore the tests need to simulate the old materials!

MOISTURE METERS

DAMP METERS

IMPORTANT!

When used on a masonry substrate Electrical Moisture Meters:

  • Do NOT record % moisture
  • Do NOT record % saturation

They record a relative reading NOT directly proportional to quantity – ie, their response is non-linear

– they are purely QUALITATIVE!!

IMPORTANT!

Conductance meters do not respond to any significance on most clean, uncontaminated inorganic materials in their air dry state even under conditions of high humidity, eg, brick, mortar, concrete, paint, wallpaper paste!! There are very few exceptions!

Different materials have different ‘air dry’ moisture contents; most are not significantly hygroscopic and will absorb only very little extra moisture with increase in humidity; this does not significantly affect meter readings as claimed in the ‘Rising damp myth’

Air dry moisture contents of some materials:

Brick:                                                                   0.1 – 1.0%

Gypsum plasters                                              0.5 – 1.0%

Old lime plasters                                              up to 2.0%

Cement renders                                               up to 2.0% (appears to depend on carbonation)

Wood (organic – hygroscopic!)                   max of 16 – 17% in a ‘dry’ environment

DAMP METERS

PROBLEMS WITH ELECTRICAL

MOISTURE METERS

They are too sensitive and it takes skill to interpret results

Erroneous results can be obtained by:

  • Contaminated salts, ie, hygroscopic salts only!
  • Some materials containing carbon or other electrically conducting material (rare and local knowledge)
  • Foil backed paper (experience)
  • Surveyor’s fingers on the probes!!!

BUT over 99% of high figures will be the result of water and/or hygroscopic salts, neither of which should be in the masonry and must have therefore arisen from somewhere!

In the book ‘The Rising Damp Myth’ it is reported that one RICS Surveyor’s notes state, inter alia, the following:

“Older properties tend to have an accumulation of surfaces salts due to years of evaporation. These salts, whether hygroscopic or not, will lead to readings on a protimeter a zone or two higher than the actual amount of water present.”

BUT

  1. Only hygroscopic salts will cause high readings. Efflorescent salts alone in an air dry substrate DO NOT!!!
  2. Where did the water come from to result in “years of evaporation”??
  3. Only a very few building material will cause an electrical conductivity meter to respond significantly in the absence of free water and/or hygroscopic salts!
  4. Over 30 years of sampling experience has shown that this reported ‘natural’ surface salt problems is not the case.

DIAGNOSING RISING DAMP

TOTAL MOISTURE CONTENT

of brick/mortar/plaster, etc, is potentially

the sum of 2 components:

  1. AIR DRY (HYGROSCOPIC MOISTURE CONTENT

Moisture in a material when it is in equilibrium with the air. It is what we

would regard as a ‘dry’ material, ie, when there is no water ingress. It is a

material’s ‘standing’ level of moisture.

  1. CAPILLARY (OR FREE) MOISTURE CONTENT

Moisture that fills the capillaries of the material. It is only present what there

is an active source of water ingress, eg, rising damp, water penetration, etc.

It is this water that usually causes problems.

bre digest 245

Principal:

If the sample loses weight it has dried out

ie, it contained capillary (free) moisture and therefore it was subject to a source of water ingress at the time of its removal

If the sample does not change in weight (or gains) it was ‘dry’ (not subject to water ingress) at the time of its removal.

bre digest 245

Note: the method basically identifies the presence of water ingress, or not –

it does not necessarily, on its own, identify specifically rising damp-and certainly not from a single sample!

The author explains the Building Research establishment Digest 245* method in ‘The Rising Damp Myth’but he has completely misunderstood how the results are interpreted!

He states that if the sample gains weight then:

“— it was contaminated with salts (and therefore possibly affected by ground water)”

(Note: could “ground water” and salts be from the ‘mythical rising damp’??)

If it loses weight the:

“–it’s moisture content was more likely due to a non-salt contaminated moisture source, such as rainwater or condensation”

The above interpretations are WRONG! For example, if the sample loses weight it simply shows that it was subject to water ingress FROM SOME SOURCE, eg, water penetration, rising damp. If it gains then it was ‘dry’ (no water ingress) and removed from a relative humidity lower than that of the test – it does no necessarily reflect salt contamination!

This could explain why the Author has never found rising damp (and never would on his interpretation), and begs the question, has he ever used the method??

*BRE Digest 245: ‘Rising Damp in Walls: Diagnosis and Treatment’

VERTICAL PROFILE TO BRE DIGEST 245
RISING DAMP AND HYGROSCOPIC SALTS
BRE DIGEST 245
BRE DIGEST 245
BRE DIGEST 245

THE GROUNDWATER SALTS

(HYGROSCOPIC SALTS)

Hygroscopic salts absorb water from the air

  •  They are rarely seen on surfaces BUT their effects are on the form of visible dampness/high surface moisture meter readings.
  • Their most common origin is rising damp, and sometimes around old chimney flues where they arise from the long tern combustion of fossil fuels

Hygroscopic salts are frequently referred to by those who state rising damp is a myth, and blame these salts, in part, for misdiagnosis or rising damp using moisture meters.

– but given that almost all building materials are effectively free from such salts, those that support the ‘myth’ never seem to explain how they only contaminate and are distributed in the lower parts of the walls!

DAMP STAINS ON ACHIMNEY BREAST, BRE DIGEST 245
HYGROSCOPIC SALT CONTAMINATION

MANIPULATING THE MYTH

Jeff Howell in ‘The Rising Damp Myth’ quotes the following:

“Bob Sharpe (1978) found that pressure injected of the damp-proofing fluid into his test pillars “ – was completely ineffective in producing a damp proof course-it was clear that no damp proof course had been established in either brick or mortar at any stage”

Sharp found that “-this had not been enough to produce an effective damp proof course”.

However, under both ‘Abstract ‘ and ‘Conclusions’ in the same paper Sharpe concluded:

“ 4. A test wall was constructed using a particular grading of washed sand in which a substantial moisture gradient was created. When this wall was injected an effective damp-proof course was formed. This could well form the basis of a realistic performance test of damp proofing treatments,”

So why the difference from the same paper?

The author of ‘The Rising Damp Myth” chose to quote from the mid-part of the paper where the test was being developed – not the final evaluation and “Conclusions”!! This is distinctly false and grossly misleading!!!

RISING DAMP, RISING DAMP MYTH

LUDICROUS OR JUST A ‘GOOD STORY’?

From ‘The Rising Damp Myth’:

“I had told him [Sharpe] that I had been unable to find a single case of genuine rising damp. His reply was short and to the point. “Well”, he said, “Neither could we”

Howell continues:

“And Bob Sharpe was the BRE’s top expert on dampness in buildings. He was the author of many papers, reports, and digests on the subject, including the landmark BRE Digest 245*, which presented the definitive official view of the diagnosis of rising damp. To hear him say that he never found a genuine case of rising damp in the British house was astonishing.-it was still odd to hear from the top expert that the whole subject of “rising damp” and – by definition – the entire workings of the British damp-proofing industry, were based on the myth.”

Note: If Howell had never found a case of rising damp then how did he describe earlier it as “typical” during his experiments in 1995?

*BRE Digest 245: ‘Rising Damp in Walls: Diagnosis and Treatment’

But:

If, as alleged in ‘The Rising Damp Myth’, that Sharpe and hence Building

Research Establishment

“had never found a genuine case of rising damp in the British house”

then one must ask:

  • How did Sharpe and BRE manage to develop tests and publish “-many papers, reports and digests on the subject” for years including Digest 245 (and earlier TIL 29) for diagnosing rising damp, about something they had never found out? (also note the author of ‘The Rising Damp Myth’ describes the Digest as “landmark” and the “definitive official view of the diagnosis of rising damp”!!)
  • Who forged and labelled the photos and data in the Digest? And who fabricated the whole story in the Digest and other BRE papers and publications over such a long period (OVER 40 YEARS) – and still going?
  • And, of course, what Government Departments authorised the funding for the BRE research, publications and their circulation over many years knowing that resulting publications by BRE where fabricated?
BRE DIDEST 245
BRE DIGEST 245

And from the RICS:

Jeff Howell tells us that, “__ Bob Sharpe — was the author of many papers, reports and digests on the subject, including the landmark BRE Digest 245*, which presented the definitive official view of the diagnosis of rising damp.”

* The diagnosis described in the Digest is based on destructive testing and lab facilities to produce vertical moisture profiles of 6-8 samples per profile, to determine the distribution of water (hygroscopic and free in each sample). In essence this is the only definitive method of diagnosing rising damp.

So in a statement from Stephen Boniface, Chair of the RICS Building Surveying Faculty, recorded in the book, Boniface reports, inter alia, “-I and others within the RICS have been lecturing for years now that rising damp is misdiagnosed in over 90/95% of cases —“ [so he says 5/10% are correctly diagnosed – but he’s previously stated rising damp is a myth!]

Given that to positively identify rising damp it requires a combinations of destructive sampling and laboratory facilities, one must ask on what objective evidence does Boniface and the others base this statement given that it is highly unlikely that they have sampled and analysed anything like sufficient properties (if at all) to objectively evaluate different forms of dampness to draw that conclusion.

Boniface’s figure is pure conjecture with no substantive validation provided!

Yet another good ‘story’?

In ‘The Rising Damp Myth’ the Author states that at Audley End in Essex, “Drilled samples shows that the wall was wet, and with the pattern of moisture distribution – wetter at the bottom and with a band of salt staining half way up it seamed to bear all the hallmarks of being affected by rising damp”

He continues, “The Building Research Establishment thought they had found rising damp in the boundary wall, but once it was covered with a tarpaulin to keep the rain off, it dried. “and” – The “rising damp” had been nothing of the sort, and the wall had simply been getting wet from the rain.”

[Note: Howell states that BRE “— thought they had found rising damp –“!!

But previously he extols BRE for producing the, “ landmark BRE Digest 245, which presented the definitive official view of the diagnosis of rising damp.”

Fact:

BRE had fully identified rising damp in this wall by analyses. They found the distinct ‘salt band’. (If it was just rain penetrating then from where did the salts and the ‘salt band’ originate in the lower part of the wall?)

During the long drought of 1984 the ground water dried out as did the wall – rising damp did not recur even through BRE wetted the ground.

Note: again, the version of events described by the Author suggest that BRE were not competent at identifying rising damp even after all their years at work in producing Digest/papers on the subject, and notwithstanding he states that, “- Bob Sharp was the BRE’s top expert on dampness in buildings.!

BRE DIGEST 245
BRE DIGEST 245

Finally, a full technical review of Rising Damp has recently been published

‘A review of Rising Damp in Buildings’

Dr Zongyi Zhang

Advanced Polymer and Composites (APC) Research Group

University of Portsmouth

A review contains over 50 worldwide references to

Rising Damp in Buildings

British Standard 6576:2005:

‘Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses’

The Author of ‘The Rising Damp Myth’ quotes the following:

“Bob Sharpe told me that there were two main reasons why the BRE was under pressure to produce rising damp in the laboratory.

The other reason was to contribute to the writing of British Standard 6576. The British Standard committee for this purpose included representatives from the major damp-proofing companies, who had themselves been unable to reproduce rising damp under laboratory conditions.” (my note: yes they did!!)

BS Committee responsible for BS 6567:

Association of Building Engineers

Autoclaved Aerated Concrete products

Brick development Association

British Board of Agreement

British Masonry Society

British Precast Concrete Federation

British Wood Preserving and Dampproofing Association

Building Research Establishment

Concrete Block Association

Eurisol – UK Mineral Wool Association

Institution of Structural Engineers

Mortar Industry Association

National House-Building Council

Office of the Deputy Prime Minister (Building division)

Royal Institute of British Architects

Stone Federation Great Britain

It is unreasonable to have one representative out of 16 from such an industry for a British Standard on rising Damp and damp-proofing!

It also begs the question why would a group of such eminent and knowledgeable organisations, including BRE, RIBA, experienced in the built environment, gather and conspire and fabricate a British Standard (in 1985 and 2005) about a matter that is, according to Howell, a complete ‘myth’ and doesn’t exist??

Review and conclusion:

Based on practical and supplied evidence from a large number of sources,

Including peer-reviewed institutions:

  1.  Rising damp is a well understood and identified feature which can occur in some buildings – it is a FACT, not a myth, and NOT originated or perpetuated by the UK damp-proofing industry
  2. Rising damp has some unique features which can be readily diagnosed using basic and authoritative analytical methodology
  3. Rising damp does NOT affect all houses without physical damp-proof courses
  4. ‘Rising damp’ has been observed and reported from at least the early 1800’s, ie for nearly 200 years
  5. Rising damp is well recorded in Australia, Belgium, Denmark, Hungry, France, Italy, Spain, indeed, across Europe, South Africa and the USA, all of which have produced authoritative peer-reviewed publications on this subject. It is not solely a UK problem!
  6. Electrical moisture meters are extremely useful as an aid in diagnosing dampness and associated problems (hygroscopic salts) provided they are used intelligently and their limitations and performance well understood.

 And the ‘Rising Damp Myth’ by Jeff Howell?

  • Very poorly researched – oblivious (or massive selective amnesia?) of authoritative worldwide peer review publications/investigations undertake by qualified scientist/engineers, and evidence of rising damp and its history.
  • Very poor science (where it even appears) and failure to understand it; no objective rigor to his ‘investigations’.
  • Non-supportable anecdotal evidence and grossly misleading ‘facts’ – some are nothing short of ludicrous and illogical.
  • Highly likely fictitious conversations/situations not consistent with publications/known history.
  • Lack of validation of so-called ‘facts’. Misquoting to support a ‘story’
  • Overall, the publication appears to reflect the author’s poorly research work in an attempt to disprove, for some reasons unknown, a well review, obvious, and a proven and readily diagnosed phenomenon recorded for at least nearly 200 years. His attempt to support his self proclaimed ‘myth’ by some ludicrous, illogical and decidedly misleading ‘facts’ is simply incomprehensible.


Knapen siphon tube system

By: admin | Posted on: December 31, 2020

Also known as British Knapen Limited, Knapen anti-damp, Knapen anti-damp proof course, British Knapen limited specialists in ventilation and anti – damp problems, Knapen siphon tubes, and also The Knapen systems for cure and prevention of damp and aeration of buildings.

There have been various damp removing systems available over the years, and the British Knapen system is quite a controversial one to say the least. Knapen tubes were installed from around the early 1900’s.

Other names of similar damp reducing products

Similar damp systems are called porous tube systems, Dalton wallguard, Holland damp proofing system, Schrijver system, Hydrotek-wallguard tubes.

This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system

From the advertising in the Knapen book

These systems are the result of many years research and experiments by Professor Achille Knapen of Belguim, and our now in such common and successful use on the continent, and have received such praise from scientists, Government, and Municipal authorities,  and clients alike, that  it is curious they have been previously so little known and practised in Britain. 

With the formation or British Knapen Ltd, however, this is the fact is now remedied. With their staff, trained under the direction of Professor Knapen himself, and with the acquisition of the rights the British Isles and the Dominions,  they are now able to offer the benefit of their experience to architects, public authorities, and the public, you so frequently have to contend with these difficult problems. A number of successful installations have already been carried out in this country by the Company, which is now organised to execute contracts at any magnitude.

British Knapen ltd was formed, and are sole proprietors for the British Isles and the Dominions of the “Knapen Systems” for the cure and prevention of damp, and for the aeration of buildings by natural forces.

The Knapen System of aeration operates on very different lines to any other method. Instead of employing force to circulate the air – the fallacy of which method has already been demonstrated-this system utilises the services of nature and operates by persuasion alone, so that it’s object is attained without bother and at little expense. Mr Knapen theorised on a totally different hypothesis from that upon which most systems based, and, recognising that there air can be displaced laterally with the difference of only 0.5° C in the temperature, a perfectly effective method of aeration was devised,  which is not subject to the disabilities of the other methods. The advantage of this method lies in the fact that the temperature on two opposite sides the building always differs (due to different orientation) and as the colder side is naturally heavier, a steady pressure is exerted, which creates a movement of the air within the building. As one side was always colder than the other, the movement is automatic and persist indefinitely, any variations in temperature as the sun moves round merely altering the direction which their moves. Thus the most perfect continuous and natural aeration of the premises is assured.

In the Knapen  System, this lateral displacement of air is utilised by the insertion of rectangular apertures in the walls, these apertures being inclined at an angle with the horizontal to take full advantage of the external air pressure, and their arrangement is such that complete change of air is continually taking place throughout the building, every particle of foul air being expelled and replaced.

Three standard positions are adopted to the ventilators. One is located near the ceiling, to deal with the lighter elements, while another set of a place near the floor deals effectively with the heavier elements. A third set of medium-sized openings are arranged between the two to complete the system. 

The apertures are protected internally by special adjustable grids so that during the cold weather when a draft or greater velocity is created the inlet can be decreased if desired. As a rule however no adjustment is needed.

The circulation is continuous, and persist day and night, year in and year out, without attention, the airflow is steady and is diffused in all directions, no current passes sufficient to cause discomfort from draughts.

It is calculated that one quarter of the cost of fuel consumed when ordinariy systems of ventilation are employed can be saved by the adoption of the Knapen system.  A comparison of the air taken from the buildings were the system has been installed, and from others where it has not been adopted, shows the difference of over 40% in the number of pathogenic microbes present in favour of the former. More striking testimony to the hygienic value of any system would be difficult to obtain. The presence of the apertures does not disfigure the elevation of the building as they are so inconspicuous has to be hardly noticeable.

One has only two talk to architects to learn how difficult problem is for them to solve. Until the introduction of the Knapen system no real remedy had been found. The effects of condensation are well-known. The decorative features of interiors are ruined by moisture which settles on the services, merchandise is destroyed by the continual dropping of water from the walls and ceilings of warehouses, while bathrooms laundries and factories suffering considerable discomfort and damage from the same cause. Condensation must not be confused with dampness. It is neither capillarity, nor absorption,  but is the automatic deposition of atmospheric moisture on cold services; quite simple matter. But a very difficult one to cure. Various remedies are employed which generally consist of lighted gas jets, hot water pipes or some other method of heating the air.  All these devices although apparently operating by warmth depends primarily on ventilators for the limited success, which proves conclusively that condensation can only be effectively combated by efficient ventilation.

The Knapen system has proved to be a really effective help in the problems of condensation. The circulation of air is so thorough and complete that suspended moisture is largely evacuated before it can be deposited on the cold services. This is no idle statement, and the British Knapen limited, asks nothing more than the opportunity to substantiate the claims in this respect. The system is successful because the problem is approached and dealt with scientifically and in accordance with the immutable laws of nature.

Effective ventilation has been achieved by the Knapen system alone. Start right, functions effectively and finishes its work to perfection. It needs no attention.

This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system
Knapen siphon tube ventilation diagram

The success of the systems

The foregoing remarks maybe interesting theoretically, but the question maybe asked “Have the Knapen Systems proved then self and practice”?   The answer is best given thus:

“In Belgium they function in the Royal Palaces, the new palaces of justice of Termonde and Louvain,  in Churches, military buildings, it is, and even in workmen’s houses. In France and equally in museums,  historic buildings palaces and other buildings to mention. The town of Antwerp, since the war, regularly specifies Knapen aeration for its new schools. In England, though introduced so recently, installations have already been made in country houses, colleges at Oxford and Cambridge, hospitals and numerous other buildings.”

The systems have received high awards and honours. Obviously, therefore, they are not only of interest to the scientist by thoroughly practical and proven.

They should be in a short time now that the British Knapen Ltd is established in Britain be the recognised installation of damp prevention and aeration in the buildings of this country.

Britsh Knapen also produced other products which are listed below.

In addition to the Knapen anti – damp proof course for the permanent cure of capillary dampness, and the Knapensystem of horizontal 

Knapen waterproof stipple

Knapen waterproof compound

Knapenite

Knapen mastic

Knapen Kalicol

What I have learnt is that this Knapen system was designed and installed according to the advertising book I own as more of a passive vent system. This being that there were tube vents at the base of the wall, tube vents at high level on external walls, and tube vents through the internal dividing walls at high levels. I only thought there was one type, and that was just to stop rising damp.

In my opinion as a passive vent system there is no doubt this would lower the vapour pressure within a building, and would most definitely help with condensation related dampness, to what extent is unknown. Whilst I have seen many of these systems installed I have actually never seen just the ventilation one. The ones I have seen installed to stop rising damp have all failed miserably though. Most of the properties I have seen would of still needed lowering of external ground levels, and removing modern masonry paint at least at low level.

I would be interested if you have any interesting comments regarding this system, and have you got any pictures of the internal vents that can be closed?

When I get 5 I will post the stuff that Knapen have produced on the rising damp system, as it might be of interest to a homeowner, or a building surveyor.

The knapen system/siphon tubes look like the below images when installed in buildings.

This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system
Knapen system and the wall is still damp
This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system
Knapen siphon tube and the wall is still damp
This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system
Knapen siphon tubes. Notes some of these have rusted through in the damp wall
This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system
Some form of damp reducing air vent

This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system
Doulton wallguard is another form of siphon tube

You might also be interested in this controversial damp proofing system also. https://www.completepreservation.co.uk/2020/12/08/magic-damp-reducing-air-bricks/

This image shows the Knapen siphon tube system. Similar system are available called Doutan wallboard, schrijver system


Magic damp reducing air bricks

By: admin | Posted on: December 8, 2020

A review and opinion of performance data relating to an environmentally controlled damp-proofing system.

1. INTRODUCTION:
In recent years there has been some significant advertising in the national press about a Patented, damp proofing system developed in Europe. Advertisements claim that it will effectively cure rising damp, condensation and penetrating damp. Similar claims are to be found on the Internet.

Holland damp proofing image,holland damp proofing, knappen damp system, porous tubes, neuraal ventilation, air bricks,  schrijver system, damp, knappen tubes, doelton wall guard, knapen tubes, knapen tubes, knapen drainage, atmospheric siphons, moisture removal system,

A European Patent was granted for the units. The Patent (EP 0 829 587 B1) describes the units in full and claims the units to be “Improved device to abstract moisture from a wall or similar, —-“: the patent then continues to describe the improvements.
The websites for the system describe it as, “– a humidity regulated system which consists of a stone element and a ceramic tube. The whole system is fixed in a specially prepared niche in the outside wall. Through an opening in the element, dry air can flow into the system. This is led directly in to the ceramic tube and two air chambers. The second opening in the system causes a draft. This leads to a drop in temperature within the tube and as a result a cold bridge is created. Since humidity tends to form at the coldest spot, it will gather in the ceramic tube from where it is transported out side by the air flow. In the same way, condensation from within the house also disappears.”

1.1 Construction:

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The element as removed from a solid wall appears to consist of a cast ‘stone’ hollow external rectangular element measuring approximately 115mm x 65mm x 40mm deep.

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A similar cast ‘stone’ square ‘bell’ is fixed in the centre by some type of adhesive; this leaves two small air slots at either side of the ‘bell’. (see photos). A thick plastic card is then adhesived into a slot at the rear of the ‘bell’. The structure is cemented into a simple slot cut into the wall with the plastic piece forming and making the centre of the 2 chambers as described, ie, the plastic simply divides the hole cut into the wall for unit’s insertion. The protruding part of the ‘bell’ is proud of the wall surface.

A number of the websites refer to an evaluation of the system undertaken by the well respected independent Dutch Laboratory, TNO (Organisation for Applied Scientific Research) in support of performance, and it is to this and their finding that this review and opinion is directed.

2. TNO REPORT DATED 4TH APRIL 1985
As part of the “Introduction” it states, “–is a piece of equipment which, when installed in the wall is intended to remove (excess) moisture with the help of the surrounding air that flows along the wall.” It further states, “To gain a better understanding of how the system works two arrangements were set up. A wall simulation with variable air speeds and variable blowing angles was used to measure the air speed at the inlet and outlet apertures as well as atmospheric pressure on the blowing plane in the system. The bricks were placed in a plastic housing. Over a period of 12 weeks comparative measurements were carried out on two identical test walls. In one wall the system had been installed. During this test the moisture consumption and the relative humidity in and behind the cavity wall were measured whilst the air speed and the blowing angle remained constant.”

Under section 2.2, ‘Measuring results’ a discussion of the results in relation to the blowing angle are given and it states, inter alia, “This shows quite clearly that the selected wind speeds of 4, 5 and 6 m/s[approximately 8 – 12 mph] the largest air displacement in the system can be achieved within a blowing angle of 30° with an optimum value of 10°.”

In Section 3 ‘Comparative measurements’ it states,
“In addition to the preparatory measurements, which are needed to explain that the way the system operates, the performance of the system was studied in greater detail in the second test arrangement. In the main this was limited to matters such as water displacement and the influence of the system on relative humidity inside and behind the cavity wall

Because it is to be expected that this is a slow process it was decided to carry out the test under the most favourable conditions possible. In doing so, it was found that when the blowing angle was 10° and the airflow had a speed of 4 m per second the system had its greatest flow rate. The atmospheric pressure, too, reached a favourable value when this angle and speed were used.”

It continues, inter-alia “Because there is a moisture barrier in the cavity wall and over the base in the spaces above can be kept free from freely evaporating moisture. This means that the moisture can only travel upwards through the walls. By insulating the cavity and the space behind it was possible to measure the relative humidity with and measuring accuracy of ± 1%.

The walls were then placed in arrangement with wind baffles under a blowing angle of 10°. Two identical fans were placed near the arrangement and via one rpm control set at an air displacement of 4 m per second. During the measuring activity the variation was less than 10%. The test arrangement had been set up in a large hall inside TNO south polder complex. This hall, with a capacity of more than 22,000 cubic metres; during the measuring work the temperature in the Hall vary between 20 and 22°C and the relative humidity between 35 and 50%. It was easy to distribute the moisture produced by the arrangement in this space without a deleterious effect on the measuring.”

2.1. The result of the comparative measurements:
Based on the TNO publish figures Table 22 in the report showed the amount of water removed under the optimum conditions they described over a period of 11 weeks was 338 ml of water per unit per day (there were 2 units in each test wall).

However, under the same conditions over eight days (not seven as stated in the report) but simply with the fans switched off, i.e. no wind passing over the wall, only 4.5 ml of water was removed per unit per day. It is also interesting to note that of the 72 ml removed in eight days, 50 ml of that were removed in just two days, i.e., nearly 70% of the water was removed in 25% of the time. If one was to recalculate the figures based on six days for the 2 units, i.e. when only 22 ml were removed, then the daily rate of water lost per unit would be only 1.8 ml, about 1/3rd of a teaspoon.

At the end of this part of the report TNO reiterate that the test was undertaken under ideal conditions of temperature and relative humidity, wind speed and angle. The report also states “In practice these measured values are subject to important restrictions”

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Further tests were carried out in relation to relative humidity and changes in physically isolated areas of the cavity and the simple isolated chamber behind the wall. The test rig is shown opposite (Figure 20 in the report). It consists of a cavity wall and a small chamber behind. The cavity and chamber are physically closed units and therefore any water evaporating from the wall will effectively be isolated within these closed areas. The wall is sitting in a water reservoir to create rising water in the masonry but the surface of the water is isolated from the cavity and space to eliminate the effects of any evaporation of the standing water into the cavity/space themselves thus vapour from the reservoir will not influence moisture in the cavity or the small rear chamber. This structure is clearly isolated from the environment in the laboratory facilities thus isolating it from any environmental factors within the laboratory facility. The temperature during the 11 week trial was reported maintained between 20-22°C and 35-50% relative humidity.

Given that the temperature is very likely to remain constant in the setup then any changes in relative humidity will be as a direct consequence of ventilation/drying the wall and not due to any changes in the external environment since the system is effectively isolated against this.

The TNO data show that over the period of around 11 weeks the relative humidity in the cavity of the treated wall dropped from 83% to 50% but in the small isolated chamber behind it fell from around 42% to 32%, a far lower drop than in the wall cavity. In the untreated wall the cavity relative humidity dropped from 95% to 82% and in the chamber from 57% to 49% which was indeed a far greater rate of drop than in the treated wall. The data are given in graphs 24 and 25 of the report.

The data show that in a sealed environment the system has a greater influence in the cavity than in the small isolated chamber set behind the wall on the ‘room’ side.

Unusually, unlike the water removal tests, the TNO makes no comment in relation to this particular test and the relative humidity changes within the cavity/isolated chamber either in the body of the report or the ‘Conclusions’ – it simply provides the figures.

3. DISCUSSION:
3.1 Rising damp:
The TNO setup as depicted above is designed to create rising damp, ie, a continuous flow of water up the wall.

The Patent granted for the system claims it is an “Improved device to abstract moisture from a wall or similar, —-“. Indeed, under conditions as used in the TNO tests this is distinctly the case in that more water is taken from a treated wall than untreated albeit under some conditions this is very minimal, and so the claim is validated. The Patent, however, does not describe any changes in performance relating to differing wind speeds, ‘blowing angles, and relative humidities: the TNO evaluation does.

However in relation to the removal of water and assessing the relative humidity in the cavity and chamber tests TNO do make it quite clear that they used optimum conditions which they had determined from earlier tests. This meant a wind speed of around 4 m per second (approximately 8 mph) and this would need to hit the wall at an angle of around 10° – these are the conditions they used for the water removal tests. Also note the conditions included 20-22°C at 35-50% relative humidity.

Their tests showed that under these optimum conditions each unit removed an average of 338 ml of rising water per unit per day. It therefore becomes obvious to do this the rate of water rise must have been equivalent to or greater than 338 ml per day, and for this to be an average the rate of rise would effectively be constant as indeed is expected from active rising damp

But under exactly the same conditions including the same rate of rise, by simply stopping the wind passing over the units (fans switched off) the rate of removal of water dropped dramatically from 338 ml per unit to 4.5 ml, a decline in performance of over 98% (well over 99% if one allows to the aberrant result as described above). This reflects a massive drop in performance and efficiency should the wind speed drop to around zero, a condition which is not uncommon around bases of buildings. So simply dropping the wind speed from 8 mph to effectively zero only around 2% of the potential water rising in the test was removed. At this level of water removal the system will prove to be of little if any benefit in removing a continuous source of water into wall. Indeed, the TNO reports clearly states in relation to the test, “–the measuring results were obtained under ideal conditions”, and “In practice these measured values are subject to important restrictions”, and it is to these latter comments in the TNO report that one must now draw attention especially since TNO clearly demonstrated the massive drop in performance with a distinct change in wind velocity.

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The wind speeds above ground level in large open spaces such as fields, airports, etc are going to be considerably greater on average than when air is passing around the base of a house in urban and rural areas where buildings are protected by other buildings, shrubs, hedges, trees and possibly the landscape itself (note: wind gauges are usually positioned high and free from obstructions which may influence wind speed/direction). Thus wind speeds of around 8 mph are sch10highly unlikely to be maintained around domestic buildings. Also note that much lower wind speeds frequently occur in the UK, again in relation to wind at ground level, i.e., at a damp proof course level. Given a property can have four sides, only two are likely to be exposed to the wind at any one time, at least two will be sheltered. Also consider that the wind direction in the UK is predominantly SW so that only part of the property will be potentially regularly exposed to wind. Indeed, many properties are well sheltered on all four sides in their own right especially at ground level. At best winds will be well restricted to some of the surfaces throughout the year – at worst restricted to nearly all. And there are days and nights, not infrequently, when there is no effective wind occurring. Also at night, and frequently during the day the relative humidity is often very high and, of course, on the cold foggy days. In all these situations the rate of evaporation via the units will significantly decline, in instances to a level where they would be serving no useful practical purpose as shown in the ‘no wind’ scenario by TNO.

Furthermore, if the units are subsequently overgrown by shrubs then the same effects will apply since such growth, if sufficient, will curtail the wind into the units, and a result of zero or near zero wind through the units might be expected with the consequential results of extremely limited water removal.

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For a given temperature the relative humidity expresses the actual amount of water in the air as a proportion of the rh_picmaximum amount it could hold; the warmer the air the more water that can be held as vapour, the lower the temperature the less. This is illustrated in the adjoining diagram. At 20ºC it becomes clear that there is much more ‘space’ for water to be taken up at 35% relative humidity than at 75%; hence drying is better at the lower relative humidity. However, at 5ºC and a relative humidity of 35% there is far less ‘’space’ for air to be taken up than at 20ºC. So drying at 20ºC at 35% relative humidity is far better than at the lower temperature of 5ºC and 35%. But at a low temperature and high humidity as found during the colder months of the year, eg, 5ºC and 85 -90% relative humidity, it becomes very clear that drying conditions are very poor – there is very little ‘space’ to take up moisture.

The process of evaporation, as used by the units, is strongly governed by the relative humidity – the lower the relative humidity, the better the drying, the greater the relative humidity the slower the drying as described above. This is clearly demonstrated by the use of a whirling hygrometer where the rate of evaporation is used to determine the relative humidity, and why clothes do not dry well outside during the colder months of the year (high relative humidity).

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As used in the tests undertaken by TNO the relative humidity was reported to be between 35-50% at 20-22°C. At this temperature these relative humidities are suitably low and would lead very good drying conditions (note the tests were undertaken in indoor conditions), and this is what their tests showed in the treated wall. But even when the conditions remained the same but wind simply stopped passing over the units in the test wall there was a dramatic drop in performance, ie in excess of 98%: thus wind speed is one of the key factors. graphs_1The likely cause was that water vapour evaporating from the wall collected in the units and reached humidities approaching 100% (saturation); effectively at such high relative humidities evaporation effectively stops and with no wind to ‘flush’ the units to constantly remove the water vapour build up the process stops and water is no longer abstracted from the wall. Under such conditions the rising water must therefore continue to rise up past the units.

Furthermore, the conditions used for the test are not regularly achieved for any length of time in the UK especially in the colder months of the year – even in summer relative humidities externally are frequently higher than 50%, and in winter frequently remain well above 70%. As a low relative humidity is very important for evaporation then higher relative humidities reduce this process leading to sub-optimal conditions especially during the colder months of the year (see opposite) Given a property can have four sides, only two are likely to be exposed to the wind at any one time, at least two will be sheltered.

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So combinations of low wind speed, low temperatures and high humidities and perhaps the wind striking the wall at a non-optimal angle would, without doubt, subject the system to long term sub-optimal conditions during which time constant and continuous sources of water ingress must simply pass by the units as under such conditions they will be incapable of operating effectively. And, like any other type damp proof course, if the rise of water is limited, their installation would not be required in the first place.

Unfortunately, the TNO did not evaluate higher relative humidities and lower temperatures to emulate conditions found in the real world environment such as those depicted in the graphs above, but in their ‘Conclusions’ the TNO report states, “The system can on the basis of the outcome of the comparative measurements, have a greater positive influence on the transportation of moisture in the wall. The system can contribute to a greater removal of moisture from wall than will be possible via the normal evaporation process. The measurements on the two test walls were carried out under laboratory conditions. In a very short period it was possible to obtain a good indication as to whether or not additional moisture was removed from wall. It is clear that the effectiveness of the system is influenced by many natural factors such as wind velocity, air humidity, temperature, etc.”

It is therefore very clear in the above statement that the investigators at TNO were aware of the influence of the natural factors of wind velocity, air humidity, and temperature which will effectively dictate the performance of the system: these are uncontrollable external environmental factors, i.e. they are uncontrollable variables which naturally change and it is these which will denigrate the performance of the system in the UK over the optimum level of performance as measured by TNO, and which they have appreciated and demonstrated. And in the real world these factors are dominant.

Finally, with reference to rising damp a paper produced in 1998 by Centre Scientifique et Technique de la Construction (CSCT, Belgium), identified, inter alia, [Google translation from French] “By definition, the effects of the above systems [the units] are limited to potentially accelerate the evaporation of water contained in the walls. These systems do not however reduce or stop rising damp. In situ tests and laboratory treatments promoting evaporation have shown questionable efficacy compared to other control systems against moisture climb” and “Used alone, this system is not in the proper sense of the word a treatment against rising damp but a process that could increase the evaporation capacity of masonry”

3.2. Condensation and the internal environment:


Warm air can hold more water as vapour than cold air, and the proportion of water that is actually present to what could potentially be held at any given temperature is known as the ‘relative humidity’.

Surface condensation is the result of moisture laden air coming into contact with a suitably cold surface. As the air is cooled the capacity of the air to hold water declines (and the relative humidity therefore increases) until at a specific temperature, depending on conditions, it cannot hold the excess of water now present; the excess water now drops out of the air as condensation onto the cold material/surface.

It is imperative to understand (1) the excess water vapour in the internal environment responsible to surface condensation is not derived from damp floors or walls (see note 1 below), and (2) the excess internal water vapour is the result of occupation (‘lifestyle’) including, washing, cooking, bathing, breathing, etc. Thus the excess water vapour is generated constantly within the property as a normal part of occupation, up to around 15 litres (nearly 4 gallons) being produced by a family per day. Wet/damp walls are not required for surface condensation to occur and indeed it occurs mostly on dry walls and as such it is very much restricted to the surface, frequently not penetrating more than a couple of millimetres on permeable surfaces, and on paint films and vinyl paper and other less permeable finishes it will remain distinctly on the surface; it does not lead to dampness through the whole thickness of the wall like rising damp.

It should also be noted that there is usually more water vapour in a building than outside simply due to that produced through occupation: water vapour exerts a pressure, the greater the amount of water vapour present the greater the vapour pressure. Water vapour moves down its pressure gradient, that is from inside the building to outside – this passage of vapour to the outside is via cracks/crevasses around windows/doors, open windows, through vents, fans, etc. It moves freely without any resistance to such movement via the above from inside the building to outside. However it will also move through the fabric of the building, ie, walls.

Water vapour moving out by open windows, fans, crevices gaps is offered no practical resistance in its movement from inside to out, that is via air to air movement (BS 5250:2002). However in order to pass through a masonry wall it has to move first through paint films, wallpaper, plaster, render, brick/stone, depending on construction, before reaching outside. These materials each offer a considerable resistance to the movement of water vapour and added together this resistance through the wall is extremely high in relation to simple air to air ventilation by opening windows or use of a fan, etc.(BS 5250:2002). Thus water vapour moves extremely slowly through a masonry wall.

In considering the TNO setup, the system as shown in the figure above is effectively a ‘sealed’ system, that is the environment within the laboratory facility has little if any access to the isolated chamber/cavity. Thus all the excess water vapour in the cavity and the isolated chamber is effectively generated solely and directly by moisture in the test wall, this moisture being significantly retained in these environments by the sealed system. What is happening is that dampness in the test walls is effectively governing the relative humidity and moisture in the isolated chamber and the cavity; there is extremely limited influence from the laboratory environment. In an occupied property the situation is reversed in that it is water generated from internal activities (see above) that governs the relative humidity/moisture vapour in the room, not dampness in a wall (even if it was to be damp in the first place – see note 1 below)

Thus, the laboratory set up does not at all reflect the real world situation where (1) even if a wall was damp/wet the water vapour from that source adds no appreciable amount to the internal environment (see note 1 below), and (2) if the wall was dry, as in most cases, no water whatsoever will be added to the interior. Thus wet or dry walls make no appreciable difference to the internal water vapour and the associated relative humidity in an occupied property.

In the case of the test walls any water in the wall is evaporating into a isolated very small volume chamber; this is rather like putting a wet rag into a small sealed plastic box, the moisture in the rag governing the moisture within the sealed box, whereas if left in an open room it would have no practical influence.

However, the isolated chamber is estimated to be around a quarter of the cubic metre (probably less) in volume. Compare this with an average room of around 50 cubic metres and with doors opening and closing, possible draghts around windows, fireplace, etc. In the test setup the surface from which water is evaporating is estimated to be around 0.5 sq metres, and this is evaporating into around 0.25 cubic metres, ie, a surface to volume ratio of 2 : 1. In a room 5m x 4m with damp rising to 1 m then we have an evaporative area of say 18 square metres evaporating water into 50 cubic metres, ie, a surface to volume ratio of 1 : 2.8; a substantial difference from the laboratory set up. Thus, the design of the experimental setup has a much greater influence than in a real world room even with rising damp with no ventilation. Also bear in mind, that unlike the TNO setup, the direction of movement of water vapour in a building is from inside to out.

The TNO test setup is actually very akin to that for checking dampness in floor/walls where a very small isolated chamber is set over the floor (or wall) to isolate and trap any minor water vapour being evaporated should the structure be damp – any accumulation of water vapour under in the small chamber is measured (British Standard 8201, Building Research Establishment Digest 163). Dampness in floors/walls cannot be assessed by measuring the relative humidity in the room as a whole since the sheer volume of water production by occupation would simply swamp the rate of loss of water from the substrate (See note 1). Also consider that relative humidity is a function of temperature and water vapour (see the figure in Section 3.1 above)

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Thus, what the TNO have simply shown is that the water vapour/relative humidity in a very stagnant confined, unventilated area against a damp substrate is almost totally governed by that dampness. They have not shown, nor do they even suggest, that the units will remove water from a room where water vapour is being continuously generated via occupation. Of course, if the wall was dry as it is in almost all cases of condensation, then the test would have shown nothing whatsoever!

However, as stated previously, it is important to understand that water vapour in a property is being continuously produced by ‘occupation’ (cooking, washing, etc); the figure opposite shows this movement. Water vapour is circulating in the room and passing down its pressure gradient where it will first come into contact with the inner surface of the whole exposed face of the wall (dry or damp) before very slowly passing through to the units set in the outer face; away from the unit it will simply continue to pass through the wall. In its passage through the wall it is very likely to pass through paint films, wallpaper, plaster, render and brick before reaching the units all of which act as a partial vapour control layer distinctly slowing down the movement. Thus any water vapour is only extracted after passing into the wall and towards the outside should it enter the unit, and not before. Furthermore water vapour entering the wall away from the units will simply continue slowly to pass through the wall, the units only being to remove water vapour locally where positioned. It is now clearly evident that the units inserted as shown will have no influence whatsoever on internal moisture production or its removal directly from where it is produced. This also means that if the surface of the wall is sufficiently cold water will condense on it well before such moisture laden air reaches the units.

The system as tested by TNO and described in the Patent cannot influence internal moisture production in a property and relative humidities/condensation, and indeed, there is no claim in either of these documents that it will do so. Furthermore basic physics dictates this is the case.

Finally it is interesting to note that unlike the test in relation to ‘rising damp’ that neither the ‘Conclusion’ or content of the TNO report, or the European Standard make any reference/ comments to the units lowering relative humidity/water vapour within a property or the units use as condensation/relative humidity control in occupied buildings.

4. SUMMARY AND OPINION:
Based on the independent TNO report and considering some basic physics and the origin and movement of water and water vapour in buildings then the following questions can be answered:

Question: Do the units abstract more water from a damp/wet wall that than one without such units?
Answer: Yes, this was demonstrated by the TNO investigation albeit under some conditions this may be very minimal, and it is also what is claimed in the European Patent.

Question: Does the system stop/control rising damp?
Answer: Its performance is totally governed by external environmental factors – wind speed, wind direction, temperature and relative humidity. This was demonstrated and commented upon by TNO. Indeed, their data showed that even under optimum conditions simply by stopping the wind the performance of the system declined by over 98%. In the UK wind speed, directions, temperatures and relative humidities are far more adverse to the system over a year than the optimum used by TNO (the influences of such factors were recognised by the Dutch laboratory); this would inevitably substantially reduce the efficacy of any installed system. The performance of such systems in relation to rising damp is also questioned in the Belgian paper. At best the units might afford some degree of intermittent control of rising water, at worst very little.

Question: Can the units cure/eliminate internal surface condensation?
Answer: No. There is no evidence produced in the TNO report that they will cure/ eliminate surface condensation in domestic buildings. The report makes no comment whatsoever on this matter in either the body of the report or the conclusions. Furthermore the Patent does not make any such claim or suggest it. Simple basic physics and consideration of moisture generation and its movement in buildings dictates that the units will have no effect whatsoever on surface condensation in domestic environments. Set towards the outer part of walls they exert no influence on the factors which lead to surface condensation in buildings, ie, internal moisture production as a result of occupation activities..

Question: Can the units lower the internal relative humidity and provide a drier internal environment?
Answer: No. There is no evidence produced in the TNO report that they will make any difference to the conditions in the internal environment. The report makes no comment whatsoever on this matter in either the body of the report or the conclusions. Furthermore the Patent does not make any such claim or suggest it. Simple basic physics and consideration of internal moisture generation in buildings dictates that the units will have no effect whatsoever on the internal environment of an occupied building (also see note 1 below). Set towards outer parts of walls they exert no influence on the internal environmental conditions/water production through occupation, the source of water for high internal humidities/condensation, and as such their installation cannot lead to a drier internal environment.

Question: Are the units the complete solution for rising damp, penetrating damp, condensation and any combination of these?
Answer: No.

[Note 1. The origin of the water contributing to a condensation problem within a building is almost always from ‘occupancy activities’, ie, cooking, washing, breathing, lack of ventilation, intermittent or inadequate heating, etc. Moisture in damp walls, floors, etc, is not considered to be a significant contributory factor to the internal atmospheric water burden of a property because the water vapour arising from such sources is usually insignificant in comparison to that arising from normal household activities. Indeed, research undertaken at Building Research Establishment, East Kilbride (C.H.Sanders – unpublished data – 6/2/01; and now published in ‘Understanding Dampness’ BRE Publication 2004) showed that the amount of water lost from a saturated floor slab was around 36g per day for a floor area of 8 m2 for still air conditions (this would only increase slightly for the minimal air movement around walls). This would compare with up to 9,500g per day produced by a single individual and up to 15,000+g by a family undertaking normal household activities, eg, cooking, breathing, bathing, washing, etc: damp walls should behave no differently. Thus water vapour losses from capillary bound water in walls is therefore of little significance, and even less where dense renders, paint films and vinyl based wallpapers further reduce evaporation. Water from such sources therefore adds a negligible amount to the overall internal moisture burden of the property; in practical terms it can be discounted.

An interesting case study of this system installed to a property in Trowbridge Wiltshire.

A couple purchased this system as they were told no re-plastering was necessary, this is very desirable considering how much work this involves.

The system was installed and they were told they would get a free check to show the system is working in a years time. The damp problems never really got any better, when the year was up they were told the walls were drying down….obviously these people trusted this company.

However 3 years down the line we were called in to see what was going on, the walls were visibly damp up to around 1 meter in height with high damp readings on the meter throughout the ground floor. It was discussed that this system has shown to have many faults, and I have personally seen a fair few issues to say the least.

The below pictures shows a black band at the base of the wall, this is a modern render touching the floor, this is also stopping any evaporation of rising dampness from the wall. Our technician is cutting this back neatly for removal of the render at low level to create wall base evaporation.

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The below picture shows the bridging render being removed.

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A small bell mouth was made to ensure rainwater will drip away from the building fabric, this has exposed the stone.

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The render was also removed on the flank wall, and a bell mouth was also introduced.

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The above pictures show very basic procedures that should have been carried out before the magic air vents should have been installed. In fact there was no need for the magic air vents that cost £3000.00.

We produced laboratory analysis following the methodology in BRE Digest 245 to prove the system wasn’t working, and that there was still rising dampness issues along with salt contaminated plaster. We worked on the principal that it was misrepresentation as they stated that no re-plastering was necessary, and fortunately my client received a full refund.

An interesting statement in their terms and conditions

7.2 In the below states that they will be measuring the brickwork for a reduction in relative humidity with a conductivity moisture reading machine (damp meter), I have never seen a damp meter that does this in conductivity mode!!!

In the report I was shown there were no conductivity meter readings so there was no way to show that the wall had dried down anyway. They also had never drilled a hole in the brick to measure relative humidity, or on the re-visit, so how could they show the wall has dried down?

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Below are some of interesting pictures regarding these magic vents

The below picture shows where there has been 2 x chemical damp proof courses installed along with magic air vents, when we were called into the property it was suffering from condensation and not rising damp. This owner had spent thousands of pounds and all they needed was simply a system 3 ventilation system installed compliant with Part F of Building Regulations.

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The below picture is actually the worse one I have ever seen installed, it is on an internal wall. The lady was told as she lets her dog out many times a day the wind from opening the door will contribute to it-so it will work.

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The below picture shows a barn conversion with 3 x modern pvc damp proof courses cut into the wall along with a later installation of the magic vents. The plastered finish was still damp because of the hygroscopic salts, unless these are removed the decorative finish will stay visually damp.

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Please remember there appear to be many of these magic wall vents systems flooding the market now, and all advertised under slightly different names. What you have to remember with most rising damp issues, the hygroscopic salts in the wall plaster are actually the visible issue. These bricks will not remove the hygroscopic salts in the plaster, so if you don’t want visibly stained plaster this will have to be removed, which is something they don’t tell you about. I have tried smoke tests on these in the wind, and also tried to cause condensation to see it they reach dew point for it to run out……I could never achieve condensation. Everybody I know that has surveyed buildings with these have never seen these with condensation running out. I was involved in job last year where somebody had these installed to a house they purchased. What the building surveyor didn’t realise, and the previous homeowner was that this actually voided the cavity wall insulation guarantee. So if wish to buy a property which has had the magic vents installed be careful. As you can imagine my client had to pay to have all the cavity wall insulation extracted, and then the magic bricks removed, along with new cavity wall insulation installed. This was a very expensive unforeseen expense.

I have also seen these cause damp to actually penetrate into the inner skin of the wall, as the duct is installed horizontal instead of a fall to the outer wall.

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The magic damp removing air brick

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Drilling around the air brick carefully, as the client wanted proof the duct wasn’t installed at an angle running out of the cavity
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Here you can see this is the duct within the cavity wall. This isn’t part of the TNA test report. So surely this goes against how it was tested by the TNA!

You can see the duct is bang on level and horizontal, so if any rain does penetrate the outer cavity wall it will run towards the inner skin. When this does happen damp will appear on the decorative surface.

The below video shows where the air bricks were installed to a property and failed to fix the damp issues. You can also see clearly with thermal imaging why they got mould issues to the wall internally opposite the air bricks as there was a massive cold bridge. You can also clearly see many building defects as to why the wall was suffering from rising damp issues. Typically these bricks are installed in 1 or 2 days normally at a cost of £2500.00 – £3000.00.

https://www.youtube.com/watch?v=m1VcCbeCg64&t=26s

If you have a damp issue, make sure the damp survey is carried out by a competent person, and that all potential causes are eliminated, along with mortar/plaster sampling (gravimetrics) following the methodology in BRE DIGEST 245. I have plenty of info regarding damp surveys on my blog posts, so you can do your research on the right questions to ask a surveyor.

If you need help with a damp survey you can contact us enquiries@completepreservation.co.uk


Deathwatch beetle sound

By: admin | Posted on: November 30, 2020

Have you heard Deathwatch beetles in the walls of your house?

In this video you can hear and see the Deathwatch beetle in action making that dreaded tapping noise. This is often heard in the early hours of the morning when its quiet. I’ve seen plenty of historic Deathwatch beetle infestations where no treatment is needed. If you think you have an issue make sure you instruct a competent person that really understands these beetles without spending money on treatments that aren’t needed.

If you think you have Deathwatch beetle issues, please click on the video below where I run through some tips for you. If you need a Deathwatch beetle survey give us a shout 🙂


Lime plastering Wiltshire/ damp survey wiltshire

By: admin | Posted on: November 10, 2020

I was recently asked to carry out a damp investigation to a property where damp issues had persisted for many years. My client had received conflicting advice from a number of different damp and lime experts. Some of this advice was to remove any modern materials and replace with lime render and lime plaster. Remove modern paint, and repoint with lime pointing putty. Other advice was to use a modern guaranteed system and damp proof walls. Another free damp survey specified to increase the ventilation in the property by installing a positive input ventilation (piv).

In this instance this is where it can get very worrying, as potentially a serious amount of money is about to spent, and neither of this is actually going to fix the root cause. This is a common scenario when a homeowner is a layperson and has no knowledge of how a damp survey should be carried out. Lets face it most people that come around to a property have a service to offer, and im sure most people are just trying to earn a living without the intention of trying to rip anybody off.

This job could have gone horribly wrong if our client hadn’t been advised by a family friend just about before she was going to have the lime plastering and lime pointing carried out to her Wiltshire property. Her friend advised her to contact me as we’ve recently helped out another friend with a very similar conflicting rising damp issue.

The damp survey

The art of any damp investigation is all about elimination of the root cause before coming to a conclusion. The well documented BRE digest 245 methodology is what I would say an averagely competent damp surveyor should follow, and this should aid any survey findings.  The reason I say this is because this methodology is recommended guidance in every British Standard in regards to damp. In this instance at this property the mortar sampling was very wet at the base of the wall (20% capillary moisture), along with a very low hygroscopic value (1.1%), with no high levels of nitrates or chlorides. By following this methodolgy and removing the plaster samples for analysis, I was able to confirm something that none of the previous surveyors, contractors, lime specialists had even mentioned. 

All of this points to either a mains leaks, plumbing leak, or drainage leak. This high amount of capillary moisture, along with a very low amount of hygroscopic value, is indicative of rising damp caused by excess water from a defect. True genuine long term rising damp always has hygroscopic salts like chlorides, and / or nitrates present.

I used our signal generator Ridgid SR20 to actually locate and trace the mains water coming from the road and into the property. Because the property had been extended, the original main was hidden under new concrete solid floors to the side extension. Once this was located I was then able to use My Aquaphon acoustic leak detection equipment all the way along the pipe to listen for any possible mains water leaks.

The property had some older original drainage systems in place, and some fairly modern drainage. I used my Ridgid drain CCTV inspection camera to inspect all drains around the property.

What I found during the CCTV inspection was that the drains were in need of urgent repair, as these defects were directly related to the amount of moisture that was producing rising damp symptoms within the property. What was good, was that my client was there and could view the camera inspecting the drainage for all the issues that I noted.

I used a tracking dye and a bung to flood the drains to exaggerate the issue, to track the path of the water. What I also found was that this drainage issue also caused damp issues to the cavity construction part of the extension also, as I was able to see it within the cavity wall.

By using Complete Preservation for the initial survey, we were then trusted to specify the repairs to the building to resolve the rising damp issues. 

As always budgets can be limited so quotations are really based on what needs to be done ASAP, and at what cost.

I specified drain patching, which was needed in numerous locations, along with connecting an old soak away to mains drainage, as this wasn’t draining as desired. 

Ground levels were lowered as per our typical drawing.

Modern masonry paint is to be removed at low level  (150mm from the floor) to aid evaporation at the base of the wall. Lime putty repointing was also specified for low level  areas where pointing was needed. 

Please see the below video of a 1 minute demo of how to remove modern masonry paint, and how to lower the high ground levels.

Top tip

Before you spend money on any damp proofing works, or even lime plastering, lime rendering, lime pointing in regards to damp issues, it would be worth paying for professional guidance to eliminate damp root causes. It would be prudent to have a CCTV drain survey, leak detection, and also mortar/plaster sampling following the methodology in BRE DIGEST 245 where needed. The reason I say this is because I’ve seen numerous lime plastering jobs fail because none of the above has been carried out. Lime plastering is a fantastic product, but it isn’t going to perform as desired when there are defective drains, and the walls are very wet. When walls are very wet it is also a good idea to use some drying equipment to lower the moisture content of the wall. 

If you need further advice regarding damp issues and lime plastering costs please email enquiries@completepreservation.co.uk


Sympathetic rising damp solutions

By: admin | Posted on: October 29, 2020

First of all lets just agree that rising damp occurs. It might get mis-diagnosed by damp surveyors, and it also might not get resolved first time.

It isn’t unusual for people to have spent a few thousand on surveys and damp repairs and still have damp issues. Elimination of all potential causes before coming to a conclusion is essential to ensure the correct diagnosis, and move forward with options of repairs.

High external ground levels are a common issue when it comes to rising damp. High ground levels contribute to the height of which rising damp can rise, as it will restrict evaporation at the base of the wall.

General external basic defects like guttering leaks, and drip detailing also need to be rectified. It is always advisable for you to monitor your building during heavy rain to see how your building is dealing with rainwater. It is easy to spot guttering defects, and possibly a blocked drain.

French drains, or French moats as many people call them actually cause more of an issue in regards to damp. This is because they never get maintained, they can’t get inspected unless a CCTV drain camera is used. If a drain blocks, and surcharges these often get filled with silt etc, and even tissues if connected to a foul drain.

The pictures below from a recent damp survey highlight the above issues with flooded French drains, silt build up, along with root infiltration.

Drains are perhaps one of the biggest contributors to rising damp issues. These rarely get inspected as generally most surveyors don’t own any drain surveying equipment.

The picture below shows a CCTV drain survey picked up the cause of this long term rising damp issue in Wiltshire. As you can see there is a damage to the drain pipe that is connected to the toilet. This cause of rising damp and a rotten suspended timber floor couldn’t of been found without a CCTV drain survey.

We understand how to find and diagnose all types of damp issues, and also have the experience, and know how on how to repair any defects.

If you need a damp survey to help locate potential causes to offer a long term solution, please give us a shout.


Drain Patching / lining

By: admin | Posted on: October 17, 2020

Complete Preservation carry out CCTV drain surveys, along with drain repairs using our unique drain lining / patching system with fast cure times. Our drain patching system is a no dig system, which means most repairs can be carried out below ground, without any disturbance to above ground areas. This can save time and money if drives, paths, and even home internal floor finishes can remain in situ. The below image demonstrates a damaged drain pipe on the left hand side, and a drain lining system that has been installed on the right hand side.

drain lining and drain patching wiltshire

Damaged drain symptoms

If you have rising damp issues on your external or internal walls, damp or flooding in your sub floor void that’s causing dry rot or wet rot, blocked drains, slow draining drains, walls that have cracking / subsidence, this is likely to be related to drain defects. These defects could be caused by root intrusion, and damaged/cracked drains, and need to be inspected and possibly be eliminated with a drain CCTV camera to prevent further issues.

We offer quantitative moisture analysis when it comes to rising damp, following the methodology in BRE Digest 245, along with all types of sympathetic damp repairs, dry rot and wet rot repair, to include drying of sub floor voids.

Contact us to discuss your issues, and we can offer you some professional guidance where needed.

enquiries@completepreservation.co.uk


Green Homes Grant

By: admin | Posted on: September 30, 2020

From today (Wednesday 30th September 2020) homeowners across England have the opportunity to apply for funding under the Government’s Green Homes Grant Voucher Scheme to make energy-efficiency improvements to their homes. The vouchers will allow homeowners to obtain funding for up to two-thirds (up to £5000) of the cost of the energy efficiency measures identified, while lower-income households including those on certain benefits could be entitled to have as much as £10,000 of the costs fully covered. It is possible that over 600,000 homes could benefit from the scheme so there is a real opportunity for our Registered Businesses to refresh their delivery practices, develop new skills, gain more customers, expand, and grow. 
What measures are covered by the Green Homes Grant?
Under the Green Homes Grant, homeowners will be able to apply for funding to improve the property’s energy efficiency. This is a significant opportunity for tradespeople who are able to carry out the following works to gather new business:External wall insulation; internal wall insulation; cavity wall insulationUnder-floor insulation: solid FloorUnder-floor insulation: suspended FloorLoft insulation; flat roof insulation; room-in-roof insulationAir source; ground source heat pumpSolar thermalBiomass boiler In addition, households can use their voucher for further energy-saving measures. These include one or more of the following:Draught proofing; double or triple glazing; secondary glazing, when replacing single glazingEnergy-efficient replacement doorsHot water tank thermostat; hot water tank insulation; heating controls
To ensure the work carried out under the scheme is of high quality that consumers can trust, all businesses need to be certified to install energy efficiency or low carbon heat measures to the relevant standards and be registered with TrustMark. They must be Publicly Available Specification (PAS) standards 2030: 2017 or 2030: 2019 certified, by a certification body that has been accredited by the United Kingdom Accreditation Service (UKAS). More information is available on the UKAS website. To install low carbon heating measures, such as heat pumps, the business must be certified with the Microgeneration Certification Scheme (MCS). Once a business is certified to the required standards, they can register with TrustMark through one of our Scheme Providers. The business will be added to the directory of certified installers on the Simple Energy Advice website, where homeowners can search and find them to obtain a quote.  Quality assurance is at the heart of everything we do, so any business undertaking work for the Green Homes Grant must be compliant with the TrustMark Code of Conduct, Customer Charter, and all TrustMark financial protection mechanisms and other Green Homes Grant Voucher Scheme Rules. More information about the Green Homes Grant Voucher Scheme Requirements for Registered Business are available below
REGISTERED BUSINESS REQUIREMENTS
Work Safe, Safe Work
Consumer confidence is essential in the success of the Green Homes Grant. As you know, the Work Safe, Safe Work scheme has been developed by TrustMark to give reassuring advice about what COVID-safety measures should be discussed and carried out when having work done in and around their property. These messages are now more important than ever.  All the campaign messaging and updated graphics can be found on the business resource hub (at the button below) to help you continue to promote the campaign. Please keep reminding your customers about the campaign. Ways to do this include:Attaching the PDF of the guidebook to any estimates you send outEmail customers who cancelled work during lockdown to provide added reassuranceShare tips from the guidebook across your social media channels, using the hashtag#worksafesafeworkMake use of the updated campaign graphics to accompany any communications you send out. These are located in the resource hub  
RESOURCE HUB
A bright future
The Green Homes Grant is a turning point in our recovery and an important commitment from the government to decarbonise properties and keep us on track to reach net-zero by 2050. It is a chance to refresh our delivery practices, create jobs, develop new skills and retrain our workforce. TrustMark is proud to be working with the Department for Business, Energy, and Industrial Strategy (BEIS) and industry sectors to support the delivery of the Green Homes Grant, allowing eligible property owners to pay for energy efficiency improvements, that will not only cut energy bills but will also create and support thousands of jobs whilst addressing the climate emergency the world is facing.

If you need advice if you think you have any damp issues that require a survey, drying down and existing defects such as leaks etc, wall tie survey, or any ventilation requirements please contact the office on 01225 769215, or email enquiries@completepreservation.co.uk


Flood restoration Wiltshire

By: admin | Posted on: September 8, 2020

A leak was noted to be coming through the ceiling of the flat above, and luckily most of the water could be drained into the wet room without damaging the floor coverings in the property.

I drained the ceiling of excess water, and then started the drying of the property. By using the Corroventa desiccant dehumidifier I could target dry the ceilings and above flooring without that much disruption. By getting the drying equipment installed within a couple of hours this then eliminated any secondary damage of mould occurring. If you need help with drying a building from a flood or leak, trace and locate, trace and access, or leak detection give us a shout.


What is BRE DIGEST 245

By: admin | Posted on: August 30, 2020

Also called BRE DG 245.

It is part of Building Research Establishment (BRE) digests on authoritative summaries of state of the art on specific topics in construction design and technology. They draw on BRE’s expertise in these areas and provide essential support for all involved in design, specification, construction and maintenance. This particular document can be purchased direct from BRE for just £15.00 here https://www.brebookshop.com/details.jsp?id=287528

This Digest considers the causes of dampness in walls and offers a positive method for diagnosis of rising damp. It suggests possible remedial measures that can be taken to avoid rising damp such as providing a complete moisture barrier by insertion of a physical damp-proof course or the non-traditional method of chemical injection. The repair of plaster damaged by damp is also discussed.

Mechanism of rising damp

For water to rise in a wall, a supply must be available at the base. If the ground surrounding the wall is saturated, this condition is achieved, but if the ground is not saturated the soil will exert a suction that will oppose
the upward capillary pull on the water in the wall. This suction is approximately equivalent to the negative pressure exerted by a column of water extending from the base of the wall to the water table. If the water table falls, the height of the moisture in the wall will drop to a new level provided there is sufficient time for equilibrium to become established. Each period of heavy rain on the ground at the base of the wall will produce a temporary condition of saturation and the water level in the wall will begin to rise again.

The level to which it rises depends on two factors: the amount of evaporation of water from a wet wall and on the resistance to the flow of moisture up the wall. If this resistance is high (as in a material with many fine pores), the effect of evaporation is most marked reducing the appearance of rising damp, but if the wall material has many coarse pores, the height of dampness will be only slightly affected by normal rates of evaporation.

Increasing the heat input to the structure will increase the rate of evaporation from the wall surfaces. The overall effect is to increase the rate of flow of water up the wall but because of the resistance to flow this is likely to be accompanied by a reduction in the height to which the moisture extends.

In addition, evaporation will occur from deep in the pores of the plaster so that the rising damp seems to disappear. In summer, hot weather will increase the evaporation rate and lower the water table so the effect of reducing the appearance of the rising damp can be even more striking.

Water drawn from the soil usually contains a low concentration of soluble salts and the rising water will also dissolve salts present in the bricks or the mortar. When evaporation occurs the salt solution becomes more concentrated at the surface and eventually the salts will crystallise out. This tends to block the pores, reducing evaporation and hence raises the level of dampness. These salts may also be hygroscopic and will absorb moisture from the air above some critical value of relative humidity so that the surface becomes wet during wet weather, although this dampness disappears when the air becomes drier again.

All this suggests that under real, dynamic conditions rising damp in a wall is often in a rather sensitive equilibrium which may be considerably disturbed by changes in the heating of the building and in the level of the water table. The presence of hygroscopic salts tends to obscure any drying associated with such changes by keeping the wall more moist than it would otherwise be. If such salts are removed from the surface by removing the old plaster, and the heating system is improved, it is likely that the apparent dramatic improvement in the appearance of the wall surface will give the impression that the rising damp has been cured when this is not actually the case. It is against this background that the correct diagnosis of rising damp becomes important.

BRE DIGEST 245 is the only way to offer quantitative moisture analysis to prove if a wall has rising damp. This is well documented in the British Standard, BS 6576, BS 5250. BRE digest 245 clearly shows multiple pictures of possible causes of rising damp where there is a physical damp proof course installed that has been bridged by one way or another.

The above image shows rising damp being caused by the damp proof course being bridged by the plaster

Obviously solid wall properties built before a physical damp proof courses were installed can still have similar causes like high ground levels, modern renders rendered to the floor etc, that can cause rising damp issues. Many older properties also had land drainage incorporated around the property which were installed if an area was deemed to be very wet, which is discussed BRE DIGEST 245. I’ve personally noted this on many of the older historic local buildings I have worked on in the area. This is an extract from my local Bye-laws of the in Warminster Local Board from 1858. Drainage of subsoil and prevention of damp. The house drainage shall be constructed, either with additional eathernware pipe drains or otherwise, as to drain the subsoil of the premises, whenever the dampness of the site appears to the Board to render this necessary; and all the rain-water shall be so drained or conveyed from the roofs of the buildings as to prevent its dripping on to the ground and causing dampness in the walls.

In addition, evaporation will occur from deep in the pores of the plaster so that the rising damp seems to disappear. In summer, hot weather will increase the evaporation rate and lower the water table so the effect of reducing the appearance of the rising damp can be even more striking.

Water drawn from the soil usually contains a low concentration of soluble salts and the rising water will also dissolve salts present in the bricks or the mortar. When evaporation occurs the salt solution becomes more concentrated at the surface and eventually the salts will crystallise out. This tends to block the pores, reducing evaporation and hence raises the level of dampness. These salts may also be hygroscopic and will absorb moisture from the air above some critical value of relative humidity so that the surface becomes wet during wet weather, although this dampness disappears when the air becomes drier again.

All this suggests that under real, dynamic conditions rising damp in a wall is often in a rather sensitive equilibrium which may be considerably disturbed by changes in the heating of the building and in the level of the water table. The presence of hygroscopic salts tends to obscure any drying associated with such changes by keeping the wall more moist than it would otherwise be. If such salts are removed from the surface by removing the old plaster, and the heating system is improved, it is likely that the apparent dramatic improvement in the appearance of the wall surface will give the impression that the rising damp has been cured when this is not actually the case. It is against this background that the correct diagnosis of rising damp becomes important

Experience has shown that it is much more difficult to diagnose the source of dampness in a wall than is generally supposed. It is particularly difficult where the presence of some soluble salts greatly complicates the situation, especially when just a damp meter is being used.

BRE DIGEST 245 is guidance on the diagnosis of rising damp on a rational basis. The basis of the method proposed is to to drill samples, from the wall and measure the free water value and hygroscopic value of the said samples. The aim is to establish whether any dampness damage is caused by rising damp as opposed to other processes, then a location away from other sources like drains, gutter leaks etc. If visible damp or high damp meter readings are located on external and internal walls, ideally many samples should be taken as multiple causes could be causing the symptoms.

Once all of the laboratory analysis is finalised, then we can produce a graph detailing the moisture, and this will help determine the damp issue.

Whilst gravimetric sampling is far superior than using a carbide meter/speedy meter, it is imperative that the guidance in BS: 6576 is used to eliminate other potential causes. An example being that perhaps gravimetrics have proved that rising damp is a cause of the decorative internal spoiling, which is the actual sympton of rising damp. The actual cause of the rising damp could still be something like damaged below ground drainage that would need to subjected to a CCTV drain survey. Gravimetrics and hygroscopic salt analysis sometimes points to there being no nitrates or chlorides present, which then points to drain issues or leaks within the property. This means that finding the root cause, and drying of the building is all that is needed, rather than removing all of the plaster and getting it replaced.

Whilst it sometimes might sound like a slow process and unduly complicated, but no simpler procedure has proved to be reliable.

Some damp issues can cost a small fortune to fix, and so can the amount of errors in damp diagnosis by damp experts. This is why it is imperative that the diagnosis is correct first time.

If you need advice regarding damp issues, give us a shout.

Please don’t contact us for free damp surveys, as this isn’t something we offer. enquiries@completepreservation.co.uk