The incidence of true rising damp Vs Induced rising damp

I  am often asked how common rising damp is and after being asked again today I wanted to outline my thoughts on this issue, since we have a damp proofing industry operating in the UK, which operates on the premise that rising damp is a common occurrence. In fact it is incredibly rare and a review of the academic text relating to this question led to the following academic review…

How common is rising damp?

 It’s important to examine the incidence of rising damp in order to understand the size of the problem. Oxley T A, and Gobert E G (1999, p.7,8) state that awareness of dampness has also been stimulated by the rise of a service industry of ‘specialist’ firms devoted to curing it. This is an industry largely directed towards curing rising damp. This is a competitive industry which uses a lot of publicity; it has spread quite widely the impression that rising damp is the main cause, or at least a very frequent cause of dampness in buildings. In fact rising damp is a relatively uncommon cause of dampness in buildings.

The 1991 English House Condition Survey carried out by The National House Condition Survey Group (1993, p.54) found that one fifth of the stock is reported as experiencing problems associated with damp. In almost two thirds of these dwellings the problems relate to rising or penetrating damp, in the remainder the problem is condensation.

Table 2.1 (below) further clarifies this by showing that 12.6% of damp properties are affected by rising damp.

 

Table 2.1 Problems with Damp                            

                                                                               Thousand dwellings (%)

 

Problem                                                             Number of Dwellings     %

Condensation/mould growth only                                 1560                     (39.8)

Rising damp only                                                          494                     (12.6)

Penetrating damp only                                                   780                     (19.9)

Combination of the above                                             1087                    (27.7)

Any problems                                                                 3921                   (100.0)

 

% of total stock                                                                                           (19.9)

Source: English House Condition Survey (1991)

Oxley T A, and Gobert E G (1999, p.1,2) state that, we have good reason to believe that only about one third of all dampness problems are due to rising damp. They further explain; in the Protimeter laboratories specimens of wallpaper and plaster are received almost daily from surveyors and local authorities for chemical analysis for the presence or absence of certain nitrate and chloride salts, which are typical by-products of rising dampness. Salts are consistently found from year to year to be present in only about one third of all specimens tested. An even lower incidence is reported by Trotman P, Sanders C, Harrison H (2004) who state that rising damp featured in 5% of the 510 occurrences during the period 1970-74; 4% of the 518 occurrences during the period 1979-82 and 5% of the 520 occurrences during the period 1987-89, an average of about one in twenty of all (damp) investigations.

Oliver A, Douglas J and Stirling S (1997, p.186) give three reasons why rising damp is not as pervasive as other forms of damp:

 

  1. The majority of buildings in the UK have some form of original dpc. Even bridging or lack of continuity between dpc’s/dpm’s would cause only localised rather than widespread incidences of rising damp in a building.
  2. Failures of these dpc’s would need to be severe and extensive to cause major and general manifestations of rising damp in a wall. There is no evidence that suggests that such failures are occurring on a large scale.
  3. The problem of rising damp in walls caused by defective or missing dpc’s can be combated by reducing the sub-soil moisture content.

 

More induced rising damp caused by damp proofers.

More induced rising damp caused by damp proofers.

General academic consensus puts the incidence of rising damp in all damp properties at around 5% but our own view based on pragmatic experience of carrying out hundreds of detailed damp investigations, using the full range of diagnostic tools puts the incidence at significantly less than 5%. General speaking I believe that earlier investigators failed to understand the difference between true and induced rising damp, which would give a falsely high incidence. Lets assume 5% is correct though, even if this were true, one in twenty damp properties affected by rising damp is relatively rare. Practically speaking, we do not find true rising damp in anything like 1 in 20 damp properties. We may encounter three or four cases a year and for each case we almost always identify subterranean leaks and consequential high ground moisture levels as the cause.

Induced Rising Damp

Theres a great irony in that an industry, that promotes the incidence of true rising damp is in our experience, primarily responsible for causing it. However, this wouldn’t be true rising damp, rather, it is what we call ‘induced’ rising damp. Whenever waterproof coatings are applied to walls that prevent moisture evaporating from that wall then the moisture has nowhere to go but up. In these situations there is no limit to the rise height, as academically accepted to be the case for true rising damp and often the first sign of this problem is damp staining breaking through at the top of the finished waterproof plaster or render system, such as in the image below. The solution for this is to undo the work done by damp proofers and remove the cementitious render from the wall to reinstate wall base evaporation. We commonly encounter induced rising damp wherever we follow in the steps of damp proofers but we rarely encounter true rising damp and where building technical details are correct then it is usually caused by high local ground moisture caused by leaking drains (foul and storm) or leaking incoming water mains.

A classic case of induced rising damp

Unexplained damp patches at high level explained when plaster was hacked of to reveal an underlying waterproof render. A classic case of induced rising damp caused by damp proofers.

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Is this what passes for a survey and damp proofing report?

How damp proofers sell unnecessary DPC injection work. 

Typical of the Reports used by the damp proofing industry to sell unnecessary retrofit DPC injection work and re-plastering.

Fig 1. Typical of the Reports used by the damp proofing industry to sell unnecessary retrofit DPC injection work and re-plastering.

We’ve had to do one inspection this week and one detailed survey relating to production of a Part 35 compliant expert witness report; in both cases this involved checking a survey Damp report that were recently provided by an East Midlands damp proofing company, Preserva. Our last involvement with this company was when we were called to re-survey a property in Nottingham after the same company had diagnosed rising damp and hacked off all the low level plasterwork from the clients walls up to waist height. It was at this point the client got suspicious and called us in. What we found was that this company had done no diagnostic work to prove that rising damp was present, they further stated that a damp proof course comprised of blue engineering bricks had failed and failed to point out where the damp proof course was bridged by soil banked against the wall. We did the diagnostic work and in fact proved that the property did not have rising damp, or indeed any significant moisture present at depth in the masonry. The property was suffering from chronic condensation damp and we specified works to deal with this issue. Preserva reinstated the plasterwork at their own expense and my client saved circa £2500 by not having unnecessary remedial treatment carried out for rising damp.

Qualifications

We’ve said this before but if you invite a CSRT ‘qualified surveyor’ into your home then you invite a chemical  salesman into your home. It took me many years to get letters after my name, whereas the CSRT (Certificated Surveyor in Remedial Treatment) can be achieved in three days with no previous experience of buildings or surveying, but apparently after three days they are now experts in damp.

It would appear that nothing has changed because again we reviewed two recently completed reports that fail to prove the cause of damp and make incredibly tenuous claims that rising damp is present. Lets analyse the first one…

Despite damp proofers specifying remedial work for rising damp, there was no significant moisture present at depth.

Despite damp proofers specifying remedial work for rising damp, there was no significant moisture present at depth.

In fact the 8 page ‘report’ is fairly standard generic text with a few comments inserted to vaguely satisfy the unsuspecting public that they have diagnosed rising damp; though they stop short of ever saying this, which is a feature we’ve found in all their reports, that we’ve reviewed. In this report their CSRT ‘qualified’ surveyor makes the following statement… “At the time of our inspection visible signs of dampness, supported by moisture profile readings obtained using an electronic moisture meter, indicated the presence of dampness to all accessible ground floor walls. This is apparently due to salt contaminated plasterwork and an apparent possible breakdown of any existing damp proof course.”

Never has the word apparent been more incorrectly used because quite clearly it wasn’t apparent since no diagnostic work had been done. The ‘surveyor’ had not carried out salts analysis to prove that salts were present in the plasterwork and in fact there was no salt migration visible on inspection of the plasterwork. Additionally, he had not carried out testing to prove that moisture was present at depth in the masonry; this is a pre-requirement before even suggesting that the existing damp proof course has failed.

Incidentally, damp proof courses do not fail, please read this… http://buildingdefectanalysis.co.uk/conservation/do-physical-damp-proof-courses-fail/

He briefly discusses moisture profiles despite the fact that you cannot obtain any useful moisture profiles using an electronic moisture meter and further fails to even mention what that moisture profile is! Is it a rising damp moisture profile, a reverse rising damp moisture profile or just a random profile? We’ll never know but since he specified unnecessary remedial work for rising damp then I think we can assume it was a rising damp moisture profile. Critically, since it was only a relative reading then the results are unreliable and more importantly they are only moisture profiles at the wall surface. Even scan meters can not provide useful or reliable moisture profiles at depth in the masonry, and this is what we are fundamentally concerned with when investigating the potential for rising damp. The unnecessary work quoted for as a result of this report would have cost the client £2996.00 plus vat and to add insult to injury they were expected to pay £75.00 for an insurance backed guarantee if they wanted optional long term protection on this unnecessary work.

Second Review

Our second review concerns a property in Derbyshire that was surveyed by Preserva in December 2015. Their observations are limited to the following internal observations, ” Chimneys were open encouraging direct rainfall to enter the building fabric. These should be capped with a vented cowl by your builder. External brickwork was very porous and was rendered on the front and gable ends. This render was in a poor condition and it was suggested that this should be removed. The property did not appear to have been constructed with any sort of damp proof course.” 

In fact these are reasonable but limited comments and whilst it’s reasonable to comment that buildings don’t have an existing physical DPC, this was not entirely true. The rear extension in fact had a physical DPC comprising of blue engineering bricks and there were a large number of other external damp related defects that were not commented on; probably because they would not facilitate the sale of retrofit chemical injection. The main part of the building may not have a physical DPC, none was visible. However buildings can manage moisture perfectly well without a physical damp proof course and in fact there are thousands of buildings in the UK that do not have a physical damp proof course but do not have a problem with rising damp.

Internal observations were limited to the following, “Dampness was noted around all external walls of the dining room and lounge areas. Moisture profiles taken with a moisture meter confirmed that dampness was a problem within these walls. This was clearly due to the defects noted above and could also be attributed to some rising moisture from the ground also.” 

Timber moisture content of 26% means that timbers are at risk of timber decay.

Timber moisture content of 26% means that timbers are at risk of timber decay.

The operative word here is “could”… works were specified for rising damp on the basis that some dampness could be attributed to rising moisture from the ground, so again we see an assumption being made in the complete absence of any credible diagnostic results. Moreover, there were internal issues that would have been obvious to any reasonably competent surveyor, not least of which was incredibly high moisture content to the timber floor joists in the cellar. We do not know what the value of this work was but you can be sure that it was a substantial sum, we rarely see quotes of less than £2.5k for this sort of unnecessary work and frequently quotes are substantially higher. We have not yet encountered a case where the work has been required.

Damp Proofing is Almost Never Required! 

 

We’ll say it again… ‘Specialist treatments for damp are almost never required and the vast majority of damp can be cured with nothing more than minor and often inexpensive building works.’

You should view any report you receive from a damp proofing company with extreme scepticism.

 

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Training in Damp Investigation and Remediation

Why chartered building professionals need their own supplementary damp training qualification and why Housing Providers should have their staff trained. 

Damp Training

Damp Training

We delivered another 4 hour lecture to undergraduates at Coventry University on November 23rd to supplement their academic learning with pragmatic site experience and to teach them a damp investigation process that can be used throughout their careers. Coventry University run one of the best RICS accredited building surveying degree courses in the UK and their statistics show that they are now one of the leading universities in the UK  for student satisfaction. We believe passionately that future generations of chartered building professionals should not be deferring specialist damp survey work to a damp proofing industry who are significantly less qualified than they are and hopefully drive home the message by using humour to make a serious point. We offered course attendees our D.A.F.T qualification, or ‘Damp and Fungas Technician,’ because we thought that after attending a short course they deserved letters after their name to show that they were damp specialists. Unsurprisingly, there were no takers but we are hopefully influencing the next generation of chartered surveyors to not defer survey work because in fact, they themselves are the future experts in this field. Building pathology is a core building surveying skill and you cannot practise isolated elements of pathology without first having a detailed knowledge of construction technology. Assessment of the building type is a critical part of any damp investigation and you need a construction related degree to underpin any further specialist knowledge you gain relating to damp investigation and remediation.

A supplementary qualification

We have also believed for some time that Chartered professional bodies should be pro-active in developing a professional supplementary qualification for Chartered building professionals interested in damp investigation and remediation. Perhaps not D.A.F.T but maybe something like D.I.P or Damp Investigation Professional. You would need to be a Chartered professional to gain this qualification so as to ensure you have the pre-qualifying knowledge of buildings and building technology. In our opinion, a comprehensive course could be delivered in two days because no supplementary training in site health and safety would be needed.  I would also suggest that a professional damp report is reviewed to ensure it complies with a recognised survey process and protocols before being awarded the final qualification. This will ensure that professionals have both the knowledge and the full range of diagnostic tools required to carry out a professional damp investigation.

We are in discussions with Chartered bodies to deliver CPD training in damp investigation & remediation and this will possibly start in February of 2016 so please watch out for this. Our aim is to give Chartered professionals, or those working towards chartered status,  the knowledge and confidence to stop deferring ‘specialist’ damp survey work, because in fact, it is not specialist at all, it is a fundamental part of any chartered professionals job role.

Damp Training within Social Housing

We have also been training social housing technical staff in damp investigation and remediation since 2006 and I wrote our course in damp investigation and remediation because as a senior manager working within social housing I saw tens of thousands of pounds being poured down the drain every year on unnecessary damp proofing works caused by incorrect diagnosis of rising damp. Moreover, these costs were repeatable at some future point in time because damp proofing companies have no interest in curing damp, they simply want to sell systems that manage damp. It was always very difficult for me to understand why an industry so concerned with cost efficiencies did not understand that this was one of the biggest potential areas to make savings on the both planned and responsive maintenance costs. Larger social housing providers cannot employ chartered professionals every time they encounter a damp property because the budget would be blown very quickly but they should have a clear focus on curing rather than managing dampness. That being said, many providers have retained our services to deal with the more complex cases or legal disputes relating to alleged disrepair or statutory nuisance.

Many housing providers carry their own technical teams, often HNC or degree qualified in a construction related discipline. We have trained hundreds of industry surveyors since 2006 and have been delighted to see these organisations completely change their approach to dealing with damp properties, they now take responsibility and have a focus on correct diagnosis to ensure they achieve a cure for the damp rather than throwing money away on unnecessary damp proofing works.

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