Rising damp……the facts
By: admin | Posted on: August 13, 2019
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.
I have massive issues with Estate Agents that offer their damp expert to carry out a free pre purchase survey, and basically give a quote to do the cheapest job. The quote is referred to as a ‘report’ and is presumed to be worth something along with the Mickey mouse guarantee. These are often a couple of pages, with no mention of any possible defects or the actual cause of the damp.
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 installed.
The below picture shows a basic issue, this being debris in the cavity that has bridged the damp proof course.
The below shows bridging of the damp proof course by the path.
The below shows bridging of the damp proof course by the plaster.
The below shows bridging of the damp proof course by the external render.
The below shows bridging over the damp proof course by mortar pointing.
The below shows bridging of the damp proof course by the screed.
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 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.