How rising damp came and went and came back again…. and again


Damp is easy to understand so… why do so many damp proofing jobs apparently fail to deliver a dry wall? Is this really the case or is there something else going on?

Rising damp in North Yorkshire

Move on.. nothing to see here… no rising damp here… move on…

Some Rising damp tit bits…

It’s true, every surveyor I meet has a tale or two to tell of a damp proofing job gone wrong, an unhappy customer with damp walls following treatment they paid for, or a guaranteed damp course with no company to honour the paperwork.

These are common complaints and have been heard for years.  For so long in fact, that there are some surveyors who now avoid any damp proofing firms, or damp proofing treatments, on the basis that ‘we’ are all snake-oil salesmen and are best avoided.

I’m a bit touchy about being called a cowboy, so we’ll gloss over that bit and get to the real point of all this; why do so many damp courses fail to work or fail to cure the problem?

This is more complex than it first appears because several factors are involved and I’ll explain if I can.

First there’s the basic fact that many damp proof courses (DPC’s), are installed where there is no rising damp to control in the first place.  This is probably the most common cause of complaint. Though many clients don’t know that this is the reason and will expect the ‘rising damp’ to be cured by the DPC they paid for, even though this is impossible. This is not the fault of the poor client; they were ‘sold’ a solution for damp and a dry wall is their reasonable expectation. The trouble is, that after complaining of a return of the rising damp… they cannot then prove that the DPC has failed, because to do this, rising damp must be found, despite the guaranteed DPC. This is a no-win situation for the client because if the wall was only ever damp through a problem of a leaky gutter, blocked cavity or condensation, no rising damp will be found and despite the wall being damp – the installer can claim that the DPC he installed is working fine.

Not satisfactory if you have a damp wall, which you’ve spent many hundreds or thousands of pounds on getting dry – guaranteed!


An electrical moisture meter in use

The meter says it ‘s damp and it is… but why?


Poor or wilfully crooked damp diagnosis is only the first reason to be fearful.

Second; there’s the chicken to our egg of bad damp diagnosis, which is poor specification or application. There may well be rising damp, but if it is caused by a bridging problem, merely injecting the wall with a chemical dpc will rarely work without some building work. Lowering path levels or chopping back render and clearing paving is not sexy and cannot be charged at a premium rate so sadly, this crucial work is often neglected. If it is, then the DPC work will usually be compromised too. This applied to the disruptive and expensive re-plastering, which is the main source of poor application or neglect.

Rising damp, will over time deposit an unhealthy concentration of minerals in affected walls, usually at the point of evaporation and in a characteristic ‘salt band’ at the height to which the damp rises. This band may contain many more times as much Nitrate and Chloride as will be found in a soil sample. Unlike the soil, which is rained on and washed of concentrations the wall is in effect a depository for this salt in a cycle throughout the years the wall is affected.  Eventually there may be quite a lot of salt in the brick or stone and plaster. Even if the very best chemical DPC in the world is installed, (or even a physical DPC) only the capillary or ‘free’ water will be reduced. This is the actual moisture which was being wicked–up the wall and is now less inclined to be so wicked, what with the capillaries being lined with silane. This leaves the salts behind, where they were concentrated and the wall stays damp, just like we do after swimming in the sea; trying to towel dry without fresh water to rinse under, the skin feels greasy and damp. This is the chlorides from the salt water absorbing and retaining air borne moisture.

The amount of water which can be retained by salts is surprisingly high, so high in fact that a wall which has a rising damp problem for decades may have as much ‘hygroscopic’ moisture in the salt band as there is capillary moisture just below that level, put there by active rising damp – in effect the salts have doubled the damp problem. Cure the rising damp and the dampness is, at best – halved in this plaster and masonry.

There it is – if the plaster is left on – and it often is; the wall will stay damp.


chemical DPC injection gone wrong

If at first you don’t succeed.. drill more DPC holes… and then more… and more.. eh… that enough boss?


Then there’s the science bit. Chemical DPC’s are a work in progress and whilst they have been around for many years they are subject to changes in formulation, application method and quality. Of course there are standards and many have ‘proven’ performance via external certification and suchlike. But – they are not a magic bullet and all the systems have ideal scenarios and less perfect ones – there is no chemical DPC which will give 100% and even the best can be frustrated by the impatience, greed or wilful negligence of the installer, be he a specialist or a DIY enthusiast.

The commercial and political reasons for ‘failure’

Finally we have the two ‘political’, or ‘commercial’ reasons that these systems seem to some,  not to work;

First – The Guarantee.

When I first started work in the damp proofing industry in the mid-seventies most companies guaranteed chemical Damp courses for twenty five years. By 1980 this was thirty years and many these days issue 25 year guarantees (in my company’s case 20 years). These guarantees have a clear roll in the demonization of the chemical damp course because they were never going to be honoured by the vast majority of those who issued them. This isn’t to say that the guarantees were issued with cynical intent. I believe that most damp proofing companies didn’t really give the matter much thought; the manufacturers of the systems sold them to installers with claims that they would last this long; several national companies offered long term guarantees and as day follows night everyone else followed suit. The market drove the lie.

Without proper insurance the vast majority of these guarantees were worth only the paper and ink on them. Most clients forgot about the damp and they only remember when either a problem arose or, they are selling the house (sometimes over ten or twenty years later) and a surveyor for a buyer asks for it or finds ‘high damp readings’. Often the guarantee is worthless because the installer has ceased trading. Outrage at being sold a product with a long term guarantee – guarantees indignant complaints and nods of agreement from all involved when it doesn’t hold water… disgraceful and cue much gnashing of teeth!

The facts are though, that despite having thousands of guarantees in circulation, I and my peer group of established damp proofing companies are not inundated with guarantee claims. This seems to confirm that guarantee claims, far from being unsatisfied and a problem, are quite rare and it’s only the frustrated claims on defunct companies which get publicity. The other side of this coin is the possibility that so many DPC’s are installed in dry walls that claims will not come about any time soon… food for thought?

These are the political matters; why would anyone in their right mind guarantee a job for 30 years, and if they did, why would anyone take them seriously? What’s done is done. I am only looking at the perception that damp courses don’t work and these are some of the reasons why that impression has gained ground.

Finally I come to the next ‘political’ reason:


poor chemcial DPC installation

Which caused more damage, the DPC holes or the cement pointing? (answer – the cement pointing damaged the stone, the holes damaged the DPC industry)


The Backlash against Chemical Damp proof courses.

That is the backlash against chemical DPC’s which has been orchestrated and supported by the some in the general surveying fraternity. These are the great and the good of the country’s surveyors. Many are chartered surveyors (RICS), though some conservation architects and the odd construction journalist is among them.

This started as a whispering grumble along the lines of ‘These DPC’s don’t work’ and ended up with some of them spouting the howler; ‘Rising damp is a myth’.

I can understand the former group; how many exasperated customers must one meet, before you become sick of chemical DPC installers and tired of seeing all those holes drilled into walls for no apparent reason? The trouble is that damp proofing contractors, RICS chaps and Architects don’t meet in the pub for a chat and nobody looked into the industry to see what was wrong (as there surely was… and is).

Instead the situation simmered on in the ranks of the tired and thankless surveyors until –  a couple or three stalwarts came out in public – “rising damp is a myth – “is incredibly rare” –  “rising damp was invented by the DPC industry” – “rising damp is rarer than rocking horse sh*t”  etc.….

The pub analogy works for me, because the type of fevered nodding of heads these claims induced will strike a chord with anyone, who’s watched a football match in the pub, when the home side are awarded a penalty – nobody objects. Thus nobody looked into what was really going on, because it affected the other side not, ‘our team’ and so the myth grew and was almost accepted.

Rising damp? nah... doesn't exist....

Rising damp? nah… doesn’t exist….


So much so, that someone even wrote a book on it that actually sold some copies and woe and thrice woe, my favourite TV show was spoiled the other night when shock horror, QI’s Stephen Fry told Alan Davies and co that “A lot of people think that rising damp is a myth”. My respect for Stephen took a plummet then, I can tell you… but in the spirit in which this post is written in I realised; Stephen reads out whatever he’s fed and it’s not his fault.

The surveying fraternity don’t get off as easy as Stephen though. They are professionals and should know better than be taken in by a well-meaning and on the face of it justified whinging. That is what it was and there was never any real investigation into the problems caused to many people, through the unregulated and somewhat shambolic way damp has been dealt with over years.

The above is not a dissertation, but I hope that one day, someone will actually take all of the facts into consideration when writing one on damp and damp proofing. I am tired of reading dissertations which focus on only one or two of the above (not that my list is exhaustive – there are more things to consider). The science of damp diagnosis is fascinating but I believe that it has very little part to play in putting matters straight.

I am spending as much time as I can in the company of these RICS chaps and such, so that I can see things from their side and hopefully we’ll all be playing for the same team before long; with the consumer winning the match.


Dry Rot.

The following are some links to the odd bit of further reading on damp diagnosis, obtaining damp advice and if you’re in Yorkshire a link or two to my little preservation business…

A typical story of how the housing market feeds the cowboy damp proofing underclass
Electrical moisture meters can be so useful
The Property Care Association web site for approved consulatants, contractors and independent damp/timber surveyors



  1. Good post Bryan………Diagnosis is key to rising damp!
    loving the pic of all the holes drilled into the brick, can’t believe that somebody would do that!!!! Suppose thats what you get if you don’t use a Property Care Association member, out of the thousands of damp proofing companies only 400 are fully qualified PCA members which explains why we see such terrible installations.
    Keep up the good work.

  2. Pete Waddy says

    It’s interesting to read your blog, as if any one does an internet search to look for further information as people would do nowadays, quickly you can easily get the impression that damp experts etc are like you say snake oil salesmen.

    Unless you can dig a bit deeper and investigate and consolidate all the information it becomes very difficult to come to an informed view. If people within the industry can’t come to a consensus then it becomes very difficult for ordinary people to know what to believe.

    I have read a few of the forums and been onto the websites of some of the people you have crossed swords with on these forums and while some of what is written may be true , a zealot like approach is simply off putting.

    From what I can see you do your best to provide a balanced view so keep up the good work.

    • Dry Rot says

      Thanks Pete,

      There are many opinions on these things and it’s true that these take some time to thread a path through. As a damp proofing contractor myself I must make sure that I try to either avoid bias or at least be up front about it so that clients, students and others can take a balanced view. Good information and opinions formed by facts and genuine data is best.

      Do please look in again. I have been so busy lately that I have neglected the blog to keep my other work up to date – the next post will look at site comparisons between electrical moisture meters used properly and gravimetric testing to see just how great the differences are in real life.



  3. Question:

    When there is a ‘problem’ with an injected dpc which is supposed to control/fix/eliminate the rising water, why is it that the plasterwork is always sent for analysis and the performance of the dpc not investigated?

    Answers on the back of a postage stamp (lol)

    • Dry Rot says

      Nice one Graham – have you got your tongue stuck in your cheek again 😉

      I’d say that the main reason is that most installers will want to know if their plaster system has failed because let’s face it – if there are nitrates and chlorides in the plaster then moisture has to be moving through it. I must admit that in cases where I’ve had problems I’ve rarely bothered with testing, because if the client has a damp wall I need to fix it. It’s only after your tutorial and the establishment of my own lab (thanks), that I do it now. That’s part of my own knowledge building really. If the plaster has failed then that is a guarantee claim and the DPC would be re-installed anyway – no point not doing that if you are sending a crew back to plaster the job – call it caution but after 38 years I hedge my bets 🙂 It’s always better to err on the side of the client wherever possible.

      thanks for looking in Graham.

Copyright © 2010 Preservation Expert. Legal Stuff: All the advice and information in the posts on my blog is made in good faith and is based on my experience and knowledge at the time of writing. However, nobody is infallible and whilst I’m confident that most of what I write about preservation issues is accurate, there’s a good chance there’ll be an error or two somewhere. I do change my mind about stuff, as I gain more experience. In view of this you must make your own decisions on whether to follow any advice I write and think about this; I could be wrong. No responsibility will be accepted by the author for any losses anyone may suffer as a result of any mistake or for the consequence of any action you take as a result of reading this blog. If you do suffer a loss, resulting from anything I’ve written, a verbal heartfelt apology will be your only compensation.