Most buildings are porous and have the ability to absorb moisture, and when a property doesn’t have an existing damp proof course, a bridged damp proof course, or debris in the cavity, rising damp could occur, or may have previously occurred.
The most important part is diagnosis of the problem, many people claim to be a damp specialist without any form of qualifications or understanding of buildings or the potential defects. You will find there are many damp specialists that are approved contractors for a chemical company, and this is often just a 1 day training course. This doesn’t make them a specialist in rising damp investigations or even remedial works, and these so called damp specialists think everything is damp, and even offer a worthless guarantee.
A damp meter is a great bit of equipment, but these are very difficult to understand. Damp meters are very sensitive to hygroscopic salts and simply getting a few high readings in the original lime plaster isn’t enough evidence to start hacking off all the plaster. Most older buildings that still have the original lime mortar in place may have had rising damp come and go, and this has deposited some of these hygroscopic salts on the wall-plaster which will give high readings when a damp meter is used.
If you look at the picture below it shows that the old original lime plaster and wall paper have high readings, these are both dry, as they have just been removed from my laboratory oven.
The most important part of the survey is the the mortar/plaster sampling, this basically means we will need to remove small amounts of mortar/plaster for analysis. A profile is drilled from the base of the wall up to around 1000mm depending on observations at the time of the survey. These small holes that are typically around 10mm, will provide the sample that we can then test in our laboratory following BRE DG 245.
What is BRE DIGEST 245? This is the only way to confirm what the issues is and also a guide to the repairs necessary.
British Standard BS 6576:2005, (code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp – proof courses), and British Standard BS 5250:2011 ( code of practice for the control of condensation in buildings ), and BRE 245 (rising damp in walls diagnosis and treatment) all state that the only way to confirm rising damp is to use the laboratory method as described in the digest. As one of around 7 people in the UK that offer quantitative rising damp diagnosis in our own laboratory you can be assured that the correct diagnosis is confirmed.
This is some very basic stuff showing diagrams that visually explain damp issues that just drilling a new damp proof will not solve. It is well documented in BRE Digest 245, BS 6576, BS 5250, THAT YOU HAVE TO FIND THE CAUSE OF THE RISING DAMP, ALONG WITH CORRECT DIAGNOSIS BEFORE YOU CAN MOVE FORWARD WITH A REPAIR.
If you have a property that is cavity construction it is essential that you have to eliminate some of the possible causes of rising damp. It is very unlikely that the physical damp proof course has failed. If you have a solid walled property, these below pictures can also be relevant in some cases especially if there is a physical damp proof course, or a chemical damp proof course has been installed.
The below picture shows a basic issue, this being debris in the cavity that has bridged the damp proof course causing rising damp.
The below shows bridging of the damp proof course by the path causing rising damp.
The below shows bridging of the damp proof course by the plaster causing rising damp.
The below shows bridging of the damp proof course by the external render causing rising damp.
The below shows bridging over the damp proof course by mortar pointing causing rising damp.
The below shows bridging of the damp proof course by the screed causing rising damp.
Some facts…. lots of damp proofing experts claim to work to BS 6576:2005 (This is the British Standard). THEY DONT, please read the below and read some facts published in the British Standard.
I have highlighted NOTE 2 BELOW.… it clearly states that a damp meter gives a qualitative reading. Gravimetric tests give more detail, this will tell you exactly what is going on. Chemical tests, this is a speedy meter or a carbide meter will only show a total moisture content. Gravimetrics differentiate between hygroscopic and free moisture contents….. this is the only way we carry out our surveys.
Please see the facts in BS 5250 regarding rising damp.
BS 5250 also nearly states that the gravimetric method gives the most reliable results.
BRE Digest 245 states the below.
Again BRE Digest 245 recommends that plaster/mortar samples are taken to determine what is exactly going on.
What do you do if you have a damp issue? A damp survey should be more of an investigation, and you should expect to pay for it. If your damp surveyor doesn’t eliminate some very basic issues you will get a quote for a new damp proof course.
Damp meters are brilliant but they beep even when the wall is dry, and just hygroscopic salts are present, and can’t tell you if the wall is damp by free moisture or hygroscopic salts.
All of the British Standards recommend that gravimetrics should be carried out to determine what is actually going on.
Top tip
If you need to have a damp survey carried out you have to ask for an invasive survey following the methodology in BRE DIGEST 245. If you don’t, it is impossible to say the exact cause of the issue and how to move forward with a long lasting repair.
If you would like your damp issues solved first time with the correct diagnosis; contact the office 01225 769215 and speak to Ross Charters to discuss your issues.
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