Beware of Misleading Damp Diagnoses
We are increasingly visiting homes where a damp proofer, or (even worse) an unqualified contractor has attended offering a ‘cheap’ survey, and has subsequently quoted for a range of expensive damp proofing works, with the favourite being the injectable Damp Proof Course, or ‘liquid DPC’. More on that in another blog post soon, but suffice to say usually it’s not required.
In the last 50 salts tests we have carried out, only 1 tested positive for rising damp, giving us a 98% pass rate.
The favourite prognosis of unscrupulous and incompetent damp proofing firms is ‘rising damp’. But what actually is rising damp?
Rising Damp
The Property Care Association, our governing body, defines rising damp as: ‘external ground water being drawn up through brickwork by what is known as capillary action’.
Ground water is from the water table and is distinct from water produced by rain, and from your taps/water supply. It’s differentiated from these other types of water by the salts, chlorides and nitrates, that are found in it. By testing for these salts, we can confirm whether damp is from ground water, and therefore rising damp, or another source.
Capillary action is when water travels through porous material, mostly in brickwork and mortar, but in many other materials too. Tiny tubes in these materials allow water to travel upwards and saturate areas above, essentially sucking moisture up, although almost never above a height of 150cm (our first thing to look for – if moisture levels are above this it’s likely coming from above).
Combine these two, and when ground water penetrates into a building from below by capillary action, you have the dreaded rising damp.
Misdiagnosing Rising Damp
The best protection against rising damp is a DPC, or Damp Proof Course. Every house built since 1966 in the UK has to have one of these by law, a horizontal barrier along the exterior of the property that prevents moisture from travelling further up into the property. These are made of various materials from bitumen, to plastic membranes and even slate. When there’s not an effective DPC in place, or the DPC has been compromised (for example by being covered over/bridged with render, or a new extension that doesn’t have one), water can travel around the DPC, then into the property and cause water damage. As an alternative to a traditional DPC, damp proofers can inject a chemical DPC into the mortar between the bricks that spreads out and creates a barrier to prevent moisture from travelling any higher.
It just so happens that anyone can buy liquid DPC injectable kits, and charge a fortune for drilling and injecting these, with many quotes we have seen varying from £1800 – £4000. As a landlord myself, I have been offered these services by painter/decorators and handymen who have no qualifications or training, and as a technician, i’ve seen them injected in the wrong areas (usually into the bricks not the mortar).
The sad reality is that most damp proofing companies and firms offering these services are completely unqualified, leading to many appointments for us where people have received poor advice previously. The most popular mistake by far is when moisture readings are high when taken lower down a ground floor wall, and reduce as they go higher; which may give the appearance of moisture from below. But this is the same distribution of moisture when you have water penetration from above! To put this into context here is a real world example from August 2024:
A client called us in following a quote from a local firm for £2900 of damp proofing work, mainly an injectable DPC due to a diagnosis of rising damp. On inspection moisture readings were high up to a height of 40cm on the external wall, tapering off to a height of 110cm. A quick survey of the guttering with a thermal imaging camera found that water had saturated the wall along a junction in the gutters directly above this area; once cleared we returned in 1 month to find that the area was drying out naturally and did not require further intervention beyond redecoration works. Total costs including the assessment to resolve the issue were £440.
When water penetrates an exterior wall, it is likely to travel downwards due to gravity, which may give the appearance of moisture travelling up from the ground, when in fact the opposite is true.
Salts Testing
As mentioned above, ground water will always contain chlorides and/or nitrates, which can be tested for; giving you a clear indication of what is causing damp/water damage at your property. If a firm can’t do this, and they aren’t PCA qualified, they should not be selling you solutions. By taking a small scraping of plaster or masonry, and testing this on site with an immediate result, we can often save customers thousands on works they simply don’t need.
What Then?
Simply put, if the salts test is negative, then you most likely either have a leak or penetrating damp due to a failure with the building’s exterior (roof, guttering, walls, etc). These are things that are usually easy to find as part of our damp assessment product. Further investigations and works such as clearing guttering, checking drainage and leak detection are sometimes required, but in more than 80% of our reports we can categorically identify the root cause of your issue.
If it’s positive, then we would first check if there’s a DPC in place, and if there is whether anything has compromised it. We recently found a new garden wall was bridging the DPC, and by placing a small membrane between the wall and the house itself, the problem was resolved. Failing that, we can find and refer you to a quality damp proofer to do these works, ensuring you don’t get taken for a ride and that works are limited to what’s needed and no more.
Why Don’t We Offer DPC Injectables?
Frankly, because we don’t think they’re needed over 98% of the time. Remora Restorations deliberately doesn’t offer damp proofing products because this keeps us impartial; we aren’t trying to sell you anything. This is unusual within the industry but is undoubtedly best practice.
Summary
Most diagnoses (98% based on our tests) of rising damp are incorrect, and expensive damp proofing works aren’t needed.
Having a proper assessment carried out by a PCA qualified technician improves your chances of getting accurate information.
A salts test is the only reliable way to confirm whether rising damp is present, and without this an estimate for installing a Damp Proof Course may not provide a solution to damp problems in your property.
Damp in your home can present a serious issue, but that doesn’t mean it always requires an expensive or invasive solution. By taking the time to get a proper diagnosis including a salts test, and considering simpler fixes, you can save yourself a lot of money and unnecessary stress. Don’t fall victim to misdiagnosed rising damp; know the facts, and protect your home and wallet from unnecessary treatments.
For initial advice, please contact Remora Restorations on 0207 8218852, or by the contact form on our website.