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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Damp in Old & Historic Buildings

Managing damp problems in old buildings

CPD Session in Nottingham

There will be an opportunity to attend a talk I’ll be giving in dealing with damp in old and historic buildings on the 19th of May in Sandiacre, Nottingham. Full details can be found on the following link

The event is being organised by Jane Newton at the CIOB, whose contact details can also be found in the link above. The event is £5 to non-members of the CIOB and free to members and students. Whether you are a practising surveyor or just have an interest in old buildings then I’m sure you’ll find it fascinating.

Screen Shot 2016-04-08 at 13.45.40

The talk should last about an hour with a Q&A afterwards. Topics that I’ll be covering are:

1. Tools of the Trade
2. The principles of moisture management
3. Back to basics: A focus on critical technical details.
4. Understanding moisture equilibrium
5. Cure or management solution
6. The holistic damp investigation process
7. A brief update on rising damp
8. Condensation damp & ventilation strategy.

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Ventilation Strategy for Managing Condensation : Part 2

Looking at Ventilation Strategy & Options

Mould caused by ineffective ventilation and poorly insulated loft space.

Mould caused by ineffective ventilation and poorly insulated loft space.

In the absence of a modern whole house MVHR (mechanical ventilation and heat recovery) system, which few of us have, then your choices for how best to ventilate your property fall to single room options such as extractor fans or vents, or a PIV system may be recommended. The vast majority of properties that we deal with will rely on standard extractor fans, which more often than not are poorly chosen, poorly installed and poorly understood.

General Principles for Ventilation

In part one we explained why opening windows is a terrible idea for managing condensation damp and why is was crucial to place equal emphasis on managing heat losses as well as air changes. With that principle in mind, where extractor fans or single room heat recovery fans are installed, they should be wired to run continuously on trickle speed 24 hours a day with boost speed wired to the bathroom lighting circuit or pull cord. In our view fans with humidistat switches or over run timers are ineffective and we never specify them. Humidistat switched fans are particularly unreliable as the humidistat sensor often gets fouled with airborne debris.

It is absolutely critical that there are no open windows, wall vents or trickle vents in any room containing an extractor fan because if there is, then the fan will simply draw air from this open vent, short circuiting the extraction process and preventing air changes in the property. The key is to ensure that air is being drawn from other rooms so ideally trickle vents should be open in other rooms not containing a running extractor fan.

Ventilation Options

Positive Input Ventilation (PIV)

PIV system in loft space

PIV system in loft space

Until recently very little research had been done to prove the effectiveness of PIV and yet it widely specified. The BRE recently set up a parallel study to investigate the performance of PIV systems and carried out trials in their Watford test house and field studies in 16 Welsh properties. The study concluded with the following key findings:

  1. PIV did not directly save any energy but may save a little when compared to conventional extraction providing the same level of ventilation exchange. This is because roof space temperatures are usually a minimum of 3OC higher than outside.
  2. Input ventilation was found to be effective in reducing relative humidity levels by around 10%RH in the test house, even when internal doors were closed. Vapour pressures reduced overall by 0.2kPa. The unit was shown to be more effective upstairs than downstairs.
  3. In the field monitored houses input ventilation was not consistently effective in reducing relative humidity. When internal humidity levels over those outside was examined, PIV was found to be effective in the most humid houses but did little in the dryer houses. Even in the cases where it was effective there were often inconsistencies between rooms in the same house.
  4. In both the test and occupied houses, the roof space was consistently more humid than outside (excess vapour pressure of about 0.1 kPa), implying that moisture was being transmitted to the roof space from the rooms below. The results showed this moisture transfer regardless of whether input fan was operating or not.This demonstrates that PIV may actually recycle higher levels of RH back into the habitable space.

I’d be understating the case if I said that results were not particularly encouraging and an interesting point that was made  is that the occupants perceived improvements or benefits were far greater than were actually proven. Clearly for some occupants there was a psychological benefit or placebo affect taking place. The last time I wrote about the proven poor performance of PIV I had damp industry salesmen stating their disagreement and commenting about how great PIV was and how they’d had a ‘masterclass,’ not just a class, but a masterclass in ventilation from someone at the BRE involved in this study but this doesn’t change the findings and we simply don’t ever specify PIV and have never needed to.

Passyfier Vents

Passyfier vent

Passyfier vent

Passyfier vents are a relativity new product, again of unproven reliability. Essentially they are an improvement on a standard open wall vent in that they are packed with rockwool which is moisture permeable but retains heat and prevents drafts  within the property. The tubing connecting the inner and outer face of the vent is sloped to the outer face of the wall to allow for drainage  of any moisture that is collected in the rockwool packing. In their own right we cannot believe that these vents will provide an effective ventilation strategy but they have to be an improvement on a standard open wall vent since drafts and heat loss will be massively reduced. In fact where open wall vents are installed we have frequently packed these vents with rockwool  insulation and received very similar benefits at very low cost.

Single Room Heat Recovery Fans

Single room heat recovery fan

Single room heat recovery fan

These are our preferred option for ventilation but are often ruled out due to cost. A  good standard centrifugal fan may cost circa £70.00 whilst a single room heat recovery fan may cost around £250.00. However they do merit one or two words of warning. 1. Some units  come with heat exchangers that occasionally require them to be removed and cleaned in Miltons fluid or similar; this may be a prohibitive requirement in specifying for the social housing sector. 2. Manufacturers claim amazing performance of up to circa 90% heat recovery but they fail to mention that higher efficiencies are only achievable at low trickle speeds. Heat recovery is incredibly poor at high speeds because the air moves across the internal heat exchanger too quickly. However given that we generally recommend continuous running at trickle speeds then this principle is perfectly geared towards installing, and getting the best from single room heat recovery fans.

Single Room Extractor Fans

Crude but effective test for extractor efficiency

Crude but effective test for extractor efficiency

These can still be fairly effective in managing condensation so long as you avoid the pit falls that most installers fall into and follow our general principles for running extractor fans… silent & continuous running at trickle speed. We commonly see cheap axial fans installed to ceiling mount locations, yet generally, axial fans are not powerful enough to move air through the length of ducting in the roof space.  We generally specify a centrifugal rather than an axial fan (though high powered axial fans are available) because we know it will be effective for ceiling, as well as wall mounting.  A crude but effective test we often carry out is to simply see if the running extractor holds a sheet of paper, if it doesn’t then in all  likelihood it is ineffective. It is also critical that silent running fans are installed because if they are noise intrusive in operation then they will be turned off. We commonly see  cooker hoods installed to deal with extraction at first floor or kitchen level but these are ineffective purely due to the noise they produce. They’ll be ran infrequently during cooking and often are not even piped to an external wall so actually contain nothing more than a charcoal filter to deal with cooking smells. They should not be viewed as a suitable replacement or alternative for a silent and continuous running extractor fan.

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Plaster Beetles

                                                                         A less well publicised visitor
Source:www.bcpa.org.uk

Source:www.bcpa.org.uk

We’re all heard of woodworm, the term used for the larvae of the destructive furniture beetle, precisely for the reason that they can be destructive but there are other forms of infestations not generally considered harmful that you may not be aware of, the plaster beetle is one such visitor. Of course, if you’ve suffered from a plaster beetle infestation then you’ll be well aware of this pest. We recently took a call from a client asking for advice on a plaster beetle infestation in a new build property. The constructor had called in a pest control company who had fumigated but the client experienced re-infestation within two weeks of the treatment.

Plaster beetles get their name from the fact that they are often seen in new properties where damp plasterwork often provides ideal environmental conditions for these visitors. Also known as scavenger beetles, plaster beetles are part of  the lathridiidae family, a family with over 1050 described species.  This particular visitor is an unpleasant nuisance rather than being harmful but nevertheless, no one would want a plaster beetle infestation in their home. The problem is not often reported on because they are relatively innocuous however we found this report relating to a new build infestation that gives a feel for how unpleasant a plaster beetle infestation can be…

“In September, the couple spotted tiny insects in the kitchen. “I went into the bathroom and saw plaster beetles all over the wall,” says Jane. “As fast as I cleaned them away, they kept on coming. They were all over the bedroom and in the kitchen. The microwave, toaster and a television were so badly infested that I had to throw them away.”
The couple were told by the council’s environmental health department to open the windows and turn up the heating, which made things worse.
“Barratt said it had never heard of this method and recommended we used fly spray. I was using 10 cans a day – and still they kept coming. We discovered orange mould under a picture frame and thick green mould under the sink,” says Jane.
At the beginning of November, they consulted an independent environmental adviser, who said that they should have just left the trickle vents open and turned the heating down to 14-16C all day. This seemed to have an effect, but they also had to buy two dehumidifers. “I can’t afford to go on paying for the dehumidifiers to be on 24 hours a day,” says Jane. “We are so upset, as this was our dream house and we just want to enjoy it.” The couple are hoping the infestation might finally be over. “But we can’t be sure, if the conditions change, they might be back.”

What we noted from this newspaper report is how badly the homeowners were advised and how wide the difference of opinion as to how these pests should be dealt with.

Identification

A range of plaster beetles. Source: bugguide.net

Since plaster beetles thrive in damp conditions then they are more prevalent during the wetter seasons but essentially, if you have damp conditions that lead to mould colonisation then there is a small risk of plaster beetle infestation. They have been a particular problem in some new homes where properties have been handed back to new owners without being properly dried out; particularly where properties have been flooded due to careless plumbers; an issue we have seen many many times in new build. Residual  construction moisture can be a temporary issue in new build properties but in the main, properties should be relatively dry unless there is or has been some additional underlying issue. Indeed, it may be that the building fabric is relatively dry but you are suffering from high levels of relative humidity that support fungal growth. Interstitial condensation can be a particular problem since mould formation can occur in hidden voids, thereby providing a hidden food source for beetle colonisation.

Plaster beetles can be anything from 0.8mm to 3mm in length and have a life cycle of 13 to 28 days. Adult beetles deposit their eggs near a food source (mould) and when larvae emerge they feed on the mould spores before eventually pupating into adults. Pupation can take up to five months dependent on the availability of food. Some types of plaster beetle are reasonably good fliers and can be attracted to light, which is why you may see them congregated around a light source or near windows.

Treatment 

Generally speaking we are not great believers in chemical treatments and prefer to deal with infestations like this in a more natural way that avoids spraying harmful chemicals in the home. Since plaster beetles feed on mould and mould is caused by damp conditions in the home then doesn’t it simply make sense to deal with the issue at source by removing the source of moisture and the source of food? Chemical treatments can never deal with the underlying cause of the problem, which is dampness and subsequent mould colonisation. Moreover we simply do not like the idea of spraying harmful chemicals in the home and the chemical effects will reduce over time, thereby requiring re-treatment since the underlying cause has not been addressed. There is also an option of heat treatment, whereby the property is heated to 45 degrees C. This temperature should kill off any plaster beetle colonies in the home but again our main concern is that this does not address the underlying cause so there may well be a risk of re-infestation.

You will need to address the underlying cause and in simple terms you should consider 5 factors:

  1. Identify and eliminate the source of moisture
  2. Promote rapid drying
  3. Eliminate the food source (If possible)
  4. Ongoing management of high relative humidity in the home.
  5. Regular cleaning protocol to aid beetle management

The source of moisture may be a plumbing leak, penetrating damp or condensation damp and if you are in a new build property, you may simply have to deal with temporary construction moisture by promoting rapid drying. You may want to consider hiring snail fans to dry out walls and a dehumidifier to mop up the excess humidity. If this is not successful then it is likely that you have a more significant underlying source of moisture that needs identifying.

If mould colonisation is obvious then treat this with a proprietary fungicidal spray to help eliminate the food source and where plaster beetles are seen then they should be vacuumed as frequently as possible to help manage the population whilst the underlying cause of dampness is being addressed.

The underlying cause won’t always be obvious, in which case you may need to call in a Chartered Building professional. If you call in a pest control or damp proofing company then you should expect to be sold chemicals or heat treatments, money that would be better directed towards correct diagnosis of the underlying cause of moisture.

Flour Beetles
Screen Shot 2015-12-22 at 10.39.00

Flour Beetle (Tribolium Castaneum). Source Wikipedia

As an aside to this blog, we were recently asked to advise on a flour beetle infestation in a kitchen. The client complained of frequently seeing larvae on the kitchen worktops but had no idea what they were or where they were coming from. Similar to  plaster beetles, they are another relatively innocuous, but nonetheless unpleasant visitor that can invade kitchen foodstuffs, particularly flour and cereal products. However, the issue of seeing larvae only on kitchen worktops gave us a strong hint as to the source of the problem… “Do you have a toaster on the kitchen worktop,” we asked? “yes, we have a double toaster” came the reply. We advised the client to open up the toaster and clean out all the old breadcrumbs that had accumulated in the base and sure enough it was packed with two years worth of breadcrumbs and a flour beetle infestation that was completely eradicated once the toaster was cleaned out and the food source was eliminated. Some of these toasters have cleaning trays in the base that can be removed for cleaning but they are simply not up to the job. Of course we’d completely understand that many would prefer to simply throw the toaster away rather than clean it out but we’re not advocating mass toaster disposal without first checking that this is the source of the problem.

 

 

 

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Ten Tips to Avoid Buying a Damp Property

Ten simple but valuable checks for potential homebuyers

OLYMPUS DIGITAL CAMERA

High external ground levels are a problem, but less so in cavity walled construction.

 

  1. Check external ground levels are not too high when compared to internal finished floor levels. If a physical damp proof course is installed then external finished floor levels should be a minimum of 150mm below internal finished floor Level. In older buildings, if no physical damp proof course is installed then this is not necessarily a problem, simply ensure that external finished floor levels are a minimum of 200mm below internal finished floor level.
  1. Make sure external masonry is not painted. Brickwork cannot dry out when it is coated with impermeable masonry paint. If it is painted then you should at least have the paint removed from the bottom three courses of brickwork. Similarly, you should generally avoid clear waterproofing products despite claims that they are ‘breathable.’ Cement render can cause similar problems and you should ensure that cementitious render is in sound condition and not bridging the damp proof course at lower level.

 

  1. Respect the buildings construction type. If it is an old building built with lime mortar then it should be repointed with lime mortar and not Portland cement. Understand that old buildings are meant to breathe if they are to dry out, and Portland cement prevents moisture evaporation and causes spalling of brickwork.
  1. Avoid buying any property that has an original rotten timber floor replaced with a retrofit concrete slab. Retrofit concrete slabs will often cause wall base damp by pushing moisture up the walls under hydrostatic pressure. Again, this is about understanding how the building was originally built.
  1. Measure the wall thickness at a door or window reveal, is it around 240mm or less including the plasterwork? If so then its likely to be solid walled and therefore more likely to suffer from penetrating damp or internal cold surface condensation issues. You may even discover some single skin brickwork, particularly on gable walls in very old buildings. Mortgage companies do not generally like to lend against these properties due to perceived structural and damp issues. Buying an old solid walled property does not mean you are buying a damp property but you should understand the implications.
  1. Find the incoming water main and see if it is Polyethylene pipe. An old building may still be on the lead water main and these are susceptible to leakage that may go undetected under the floor of the property for quite some time. Many of the worst damp problems we’ve encountered have been caused by leaking water mains.
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Rising Damp? Technically no, since this was caused by a leaking lead water main buried in the subfloor

  1. If the property is cavity walled, is cavity wall insulation installed? CWI can occasionally cause penetrating damp, particularly the blown fibre variety. However, when correctly specified and installed we still believe it is a worthwhile addition to most suitable properties.
  1. Check your airbricks! Timber floating floors should as a general rule of thumb have airbricks installed every 2 linear metres to ventilate the subfloor and prevent timber decay. These are a critical technical feature so don’t ignore them!
  1. Has the property been treated with retrofit chemical injection? You will know the obvious telltale signs such as a row of plastic plugs installed into the brickwork at low level but what you may not know is that this is a two-part system that includes the application of internal waterproof renovating plaster. This renovating plaster dams in the damp and often gives the appearance of a dry wall at surface when in fact the underlying wall can be saturated. These management systems are almost never required despite the volume sold, and can prevent walls from drying out so don’t kid yourself that these treatments are a good thing. They are a management solution rather than a cure and as such are destined to fail.
  1. Know that condensation damp is the biggest cause of dampness within properties. To combat this, ensure that the property is well insulated, has a fully controllable central heating system installed and has a means of controlled mechanical extraction installed in the kitchen and bathroom areas.
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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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Tramex MRH III Review

Field Test of Tramex MRH III Moisture & Humidity Meter

Tramex MRH III with Accessories

I can’t imagine that I’ll be doing a lot of product reviews through this blog and just to declare any interests, I was recently handed a Tramex MRH III to try out. I actually said at the time that I’d write a review but if I didn’t like it then I didn’t like it… Tramex didn’t seem worried and the brand certainly isn’t new to me, I already own a concrete moisture encounter and a Hygrohood. The Hygrohood in particular is a far better product than its nearest competitor, which I also own.

Tramex is one of those brands that doesn’t seem to have quite broken through in the UK but they’re incredibly popular in the states. The market in professional damp meters in the UK seems to be cornered by Protimeter and has been for a number of years. Indeed, most of my equipment is Protimeter. I have a Surveymaster, a Protimeter mini and a Hygromaster, all of which I have used for a number of years. When you use this equipment as often as I do then you can get very comfortable both with the feel of the equipment and your own interpretation of results. I wrote a damp investigation process based on relative readings obtained from using the Protimeter in pin mode so that if pin readings of 20R/R (Relative reading) or above are obtained at surface or using deep wall probes then the investigation moves to the next stage. Therefore one of my key questions was with regard to what meter reading on the Tramex MRH III would equate to the 20 R/R reading on the Protimeter. Also how quickly would I get comfortable in using this equipment and interpreting results?

Screen Shot 2015-10-07 at 22.52.24 I’m also interested in any available calibration process, particularly as it relates to the humidity probe because I’ve not previously had the ability to check the accuracy of my Protimeter humidity probes and have simply renewed them occasionally to pre-empt any potential issues of inaccuracy. The MRH III came supplied with this clever Hygro i calibration device. Essentially this is a vessel filed with salt and water that cleverly maintains the internal environment at 75%.  This isn’t a portable device, you’re meant to leave it in the office and occasionally take your meter in to check calibration. I though this was a big plus and in fact it even allowed me to check calibration on my Hygromaster which read  73.6% RH  when tested with this calibration device.

On paper, the MRH III does just about everything that you would want a professional moisture meter to do, it is a Hygrometer, a non-destructive scan meter, a pin probe meter for taking surface moisture readings with a second attachment for using deep wall probes in pin probe mode. Scan mode switches between a number of modes, roof, masonry, drywall, wood and laminate; all fairly self explanatory. However what I found when using the various modes is that this meter is incredibly versatile and far more informative than the Surveymaster I am currently using.

Deep wall probes confirming that hidden masonry is damp.

Drywall mode has a much deeper scan facility than the survey master, which is fairly useless on stud walling. I was surveying a property where a number of damp walls had been hidden behind dry lining and the MRH III gave a clear indication that the hidden walls were damp. This was confirmed (relatively speaking) with deep wall probes. You are immediately struck by the excellent build quality of this equipment and the robustness of the attachments. Electrical leads look like high quality gold plated phono leads and the deep wall probes made the Protimeter version look poor by comparison. Indeed I have had a number of problems with the leads separating from the ends of the Protimeter probes but you just can’t imagine that happening with the Tramex version.  For surface readings the MRH III doesn’t have the traditional arrangement of pins protruding from the end of the meter. Instead there is another high quality attachment that is quickly attached. I carried out a number of readings with this pin probe attachment and compared them to readings obtained with the Protimeter and interestingly what I found is that relative readings mirrored one another up to around 30%. At this point we started to see divergence between the readings obtained. The Protimeter threw in the towel and generally read off the scale whilst the Tramex didn’t.

OLYMPUS DIGITAL CAMERA

MRH III & Surveymaster Readings compared

The Tramex became far more controlled and gave qualitative readings throughout the relative scale reading up to 100%, whilst the Protimeter just read off the scale and gave no real qualitative results beyond the fact that the wall might be very damp. There is no real mid-range and tendency to read off the scale at high levels and  a good analogy might be that It’s similar to conversing with someone who can only whisper or shout.

In the adjacent image you can see where the Tramex was showing a qualitative result of 35.8% where the Protimeter was pretty much reading off the scale. This was a general problem with the Protimeter, that once a certain level of moisture was reached, the Protimeter simply read off the scale thereby reducing the ability to interpret results. I spent a day comparing results and also comparing the Tramex relative readings to total moisture contents obtained from calcium carbide testing and I found that it was far better controlled and had a far better data range than the Surveymaster. Arguably this is the older Surveymaster and there is a face lifted MK II version and I’m unsure if there were any internal modifications made to the electronics. My understanding is that this was purely an aesthetic change to the casing and I saw no reason to upgrade to the Mk II at the time they were released.

OLYMPUS DIGITAL CAMERA

Timber moisture content mirrors Surveymaster results.

When checking timber moisture content I found that the Tramex and Surveymaster mirrored each others readings almost exactly which was comforting but the Tramex does provide the ability to adjust for timber species when used in scan mode. A  function that I’ve not fully explored yet.

In one kitchen wall I tested a wall base using the MRH III in scan mode and received a Medium dampness reading of 57. The wall was affected by mould colonisation due to cold surface condensation and I’d also previously obtained high surface readings in pin probe mode of 31%. Interestingly when testing the wall moisture content at depth  with calcium carbide I recorded a reading of 0% proving that the wall was dry but the plasterwork was damp due to chronic condensation. This appears to indicate that when obtaining only medium damp readings in scan mode that only the plasterwork is damp  and not the underlying masonry but again, readings can depend on the density and type of plaster installed but more testing

MRH III in masonry scan mode

will help me gain that confidence in interpreting results and getting a generalised feel for how it performs. Of course as with all electronic moisture meters, there will always be anomalies that throw up false positive readings, the presence of salts or carbonaceous materials will cause a false positive reading but so long as you do not rely 100% on these meters for diagnosis then this is not a major issue.

Condensation risk assessment with Hygro i.

A condensation risk assessment was also carried out using the Tramex in Hygrometer mode and I had the comfort of knowing that the probe was calibrated and the relative humidity readings were accurate. Similar to the Protimer Hygromaster, the MRH III also has an option for using hygro sleeves to take ERH readings in floors or walls. It’s useful that sizes of the sleeves appear to be standardised at 16mm.  The Hygro probe attached with a multi plug connector and again this is a simple  and quick connection and I noted that the meter immediately switches to Hygro mode once connected. Readings can be easily seen with or without the backlight function, which is a useful option.

I possibly haven’t fully assessed the capability of this unit yet but even at this stage I am completely won over by its versatility and build quality; it feels like a professional & durable piece of kit and I am already favouring its use over the Surveymaster because it is far more controlled across a broader scale of moisture content and gives me a wider range of options. Of course this replaces two tools currently in my diagnostic kit, the Surveymaster and the Hygromaster.

Chartered professionals have always tended to favour the Protimeter and for those wanting something to carry in their pocket perhaps that will continue but the bare MRH III will fit in your coat pocket if you only want to use the meter in scan mode, and to be frank, if you only ever use a damp meter in scan mode, as some valuation surveyors do, then this is gives a far better range of scanning options than the Protimeter equivalent.

From my perspective, this a serious piece of kit that should be considered by any serious damp investigator and suddenly my Protimeter equipment doesn’t feel quite as professional as it once did, when compared to this Tramex equipment. I’ve forgiven my Protimeter equipment for a number of niggly flaws, the cap constantly falling off the Surveymaster, poor electrical connections on the Hygro extension lead and poor quality connections to the deep wall probes, possibly because the equipment has in all other respects has been electronically reliable. Build quality feels so good with the MRH III that I can’t see these niggly faults occurring but time will tell. I’m very surprised to say that I’m now a convert  and  if I was now starting from scratch with regard to choosing a moisture meter then I’d almost certainly choose the Tramex over the Protimeter alternative. I genuinely think that the MRH III is  a fantastic bit of kit, it is well designed, well engineered and incredibly versatile.

 

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Do physical damp proof courses fail?

Why DPC Injection Work is Rarely Required. 

The damp proofing industry in the UK commonly promote two statements that are fundamental to this industry. Firstly, they promote rising damp as a common occurrence and we can comfortably state that this is simply untrue. It is an academically proven fact that  rising damp is incredibly rare.

The second claim, which is also fundamental to an industry that sells retrofit chemical injection and re-plastering is that physical damp proof courses commonly fail.  We have reviewed many many reports from these ‘specialist’ companies and the absence or failure of an existing physical DPC is commonly cited as justification for installing a retrofit chemical injection system. Moreover, you have all commonly seen retrofit chemical injection work installed where physical DPC’s already exist.

Do Damp Proof Courses Fail?

Bitumen felt DPC

Bitumen felt DPC

Originally pointed over but extrusion has blown the mortar. This DPC has not failed.

Very old slate DPC

Very old slate DPC

Fully functional slate DPC but bridged by rainsplash due to high ground levels

Hidden slate DPC

Hidden slate DPC

Physical DPC simply bridged by soil banked against the wall. Guess what the solution is?

Functional Slate DPC

Functional Slate DPC

DPC still fully functional despite being bridged by OPC mortar at the bed joint.

Visibly Functional Slate DPC

Visibly Functional Slate DPC

Despite localised flooding due to a blocked gulley.

New Polyethylene DPC

New Polyethylene DPC

New plastic DPC's are commonly bridged by poorly informed builders

Correctly installed Polyethylene DPC

Correctly installed Polyethylene DPC

DPC installed with the required overlap to prevent bridging at the bed joint

Damp proofers

Damp proofers

Why let the presence of a functional DPC get in the way of selling you another one.

More pointless injection work

More pointless injection work

Injection work of this sort is inappropriate for old properties and nothing short of vandalism.

No physical damp proof course present

No physical damp proof course present

Not a problem in this windmill provided the wall base had been allowed to breathe.

Cracked rainwater gulley

Cracked rainwater gulley

The lack of a physical DPC need not be a problem if local ground moisture is managed.

High ground levels and blocked gulley

High ground levels and blocked gulley

The solution to dealing with wall base damp very rarely needs 'specialist' treatments.

No DPC present & high external ground levels

No DPC present & high external ground levels

A problem that was cured by reinstating critical technical details.

Bitumen DPC

Bitumen DPC

Extruded from wall but fully functional

There are of course legislative requirements for the insertion of a physical dpc in new buildings. Approved document C, Section 5.2, states that walls should: resist the passage of moisture from the ground to the inside of the building; and not be damaged by moisture from the ground to any part which would be damaged by it. This requirement is met if a damp proof course is provided of; bituminous material, polyethylene, engineering bricks or slates in cement mortar or any other material that will prevent the passage of moisture.  However, relatively speaking this is modern requirement and we have many thousands of properties in the UK that do not have have a physical damp proof course installed and yet they manage moisture perfectly well despite non-compliance with the modern requirement for a physical DPC.

I personally carried out a comprehensive review of this very question and  what became clear is that the majority of academic commentary cited bridging rather than failure as the key issue, in fact it is fair to say that there was general agreement on this point. We  found only two cases where commentators cited their view that DPC’s fail, in both cases these were unproven opinion rather than proven fact. Here is an opinion given by Trotman P, Sanders C, Harrison H (2004)…  Physical dpc’s can fail occasionally, particularly those formed by engineering bricks or overlapping slates, following breakdown of the mortar; bitumen felt dpc’s can become brittle with age.  The ‘breakdown of mortar’ is the most interesting point in this statement but the idea that an engineering brick can fail is simply wrong. The authors do not go on to explain their point but we can only assume that this idea is linked to occasional building movement that results in cracked engineering bricks at DPC level. A crack in a brick or a slate DPC will not result in capillary rise in those units and we are firmly of the opinion that engineering brick DPC’s do not fail. Moreover they are the simplest physical DPC to visually inspect. The key controversy must focus on hidden DPC’s installed to the mortar bed joint. These can be formed from a wide range of materials including poured bitumen, bitumen felt, lead, copper, overlapping slates and probably one or two more that currently escape my mind. They are  often not even visible at the bed joint and this may be due to being hidden by high external ground levels, or more commonly, they have been pointed over. Both issues are clearly bridging issues rather than DPC failure and if you have a bridge then the simple solution to that problem is to remove the bridge.

To my knowledge no one has carried out a piece of research into alleged DPC failures and published their findings. It can’t be done by the damp proofing industry because they have a vested interest in promoting the idea of DPC failure. It would need to be an independent piece of work  that to my mind would be a valuable piece of research. I have considered co-ordinating this with a demolition company so that every time a building is taken down we can thoroughly inspect the DPC in the process. We have removed bricks from walls on many many occasions to inspect cavities and where we do this we have consistently found the old physical DPC to be intact and fully functional.

We have previously written that Portland cement degrades over time, initially it is resistant to rising damp until after many years of degradation it then becomes the major moisture pathway for rising damp. Where a continuous physical barrier is installed then clearly this is not a problem but this fact may well form at least a partially valid argument towards a claim that an engineering brick DPC has failed. Technically there would be nothing wrong with bricks but the mortar perps may allow rising damp via diffusion. Interestingly we have seen where perp joints have been left open on engineering brick DPCs and this would completely mitigate for this potential issue.  However, in all alleged cases of DPC failure,  what we commonly recommend is that so long as there is a provision for adequate wall base ventilation then this does not become an issue. It is all about maintaining moisture equilibrium, which is ensuring that moisture is evaporating off the wall as fast as it is rising.  Similarly, where we find that physical DPC’s are hidden we simply treat the building as though a physical DPC is not installed so that if external finished floor levels are a minimum of 200mm below internal finished floor level then this need not be a problem. There are thousands of properties in this country that perform perfectly well without a physical DPC and they generally do so because moisture equilibrium is maintained in their walls due to the fact that they are left bare, they are correctly  repointed with lime mortar, there is adequate subfloor ventilation, external finished floor levels are not too high and local ground moisture is managed.  You can of course apply all or most of these principles to a building that has a physical DPC installed, even one that has allegedly failed and you would mitigate for the alleged failure.

We are lucky enough to carry out a great deal of survey work on the Crown Estate. We deal with some very old historic buildings that were originally built to a very high standard. We are seeing properties over 150 years old where ordinarily we would not expect to see a physical DPC installed but on this Estate they do,  and this gives us a rare insight into some quite unique properties. Many of the images contained within this blog are from the Crown Estate and we are consistently finding perfectly functional DPC’s in some of the oldest properties to have physical DPC’s installed.  I may not have proven through this blog that physical DPC’s don’t fail but I can state with certainty that no one has proved that they do. We do not believe that physical DPC’s fail so if one is installed then you should give careful thought as to why you would even consider installing another unproven retrofit chemical injection system in the absence of any proof that the existing physical system has failed. We have always taken a balanced view on retrofit DPC injection because pragmatically there are times when lowering external ground levels may not be an option but the fact remains that we very rarely have a need to specify these management solutions because our focus is always on curing rather than managing or hiding the problem.

 

 

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The Damp Industry Con & The Con Surrounding the Damp Industry Con

Hand held electronic moisture meters have a part to play in any credible damp investigation process.

Hand held electronic moisture meters have a part to play in any credible damp investigation process.

The Damp Industry Con

 

There is a business that regularly posts videos on Youtube, very alarmist video’s about how the damp industry are conning people and about how the hand held electrical moisture meter is the tool of choice that allegedly provides the evidence that properties are suffering from rising damp. One might be forgiven for thinking that the poster of such material was qualified with a construction related degree and Chartered membership on a relevant professional body, but despite describing himself as being ‘uniquely qualified’ to survey for damp, he is in fact completely unqualified at even the most basic of levels. He will use words like ‘heritage’ or ‘conservation’ or ‘breathability’ because those are the good buzz words that prove that he must know what he is doing and even claims to be an expert in old properties. As has been pointed out before being a self appointed ‘expert’ does not make one qualified;  we’ll call this salesman, Mr Heritage. One of my clients recently contacted this salesman with a view to carrying out a survey on a 400 year old property. When they appointed us they asked if we knew Mr Heritage and were surprised to find out that he was completely unqualified.

Mr Heritage will often refer to the damp meter as a ‘salt’ meter, presumably to let us all know that they don’t actually measure damp, which of course is true, but to claim that they only measure salt levels is absolute nonsense and dare I say it, a con, because this particular unqualified ‘whistleblower’ is also trying to gain public trust and business from false information. Essentially, we have the public being made aware of one con on the back of another con used as supporting evidence.

A Credible Damp Investigation Process

Here again is a professional damp investigation process flow charted out. Electronic moisture meters and calcium carbide both fit into the process though clearly you could not diagnose rising damp by using a moisture meter in isolation; thermohygrometers have no part to play in this investigation process related to testing for moisture at depth in masonry! Anyone who thinks that electronic moisture meters do not have a valuable part to play in the investigation process does not have an efficient investigation process and probably doesn’t understand the process.  It is rather simplistic to state that electronic moisture meters were not developed for measuring moisture in masonry and whilst this is technically correct, modern professional moisture meters are sophisticated instruments specifically developed for taking relative moisture readings in buildings and a whole range of materials, including masonry. It’s all very well to sensationalise the idea that moisture meters are being used  to con the public and that they are not meant for use in masonry but the fact is that they are! It is simply that they only measure relative readings and the assessment of relative readings  forms a clear part of the investigation process. It is the operator at fault and not the tool!

Screen Shot 2015-07-05 at 09.42.04

Damp Investigation Process Flowchart

 

 

 

 

 

Damp Experts

I am not a fan of the damp proofing industry and believe that the vast majority of damp proofing industry operatives are completely unqualified to be diagnosing damp of any sort. This is the great damp industry con because there is actually no qualification available to become an expert in damp diagnosis but a construction related degree should be bare minimum starting point, simply because the starting point of any damp investigation is the assessment of the building technology and build type. If there is an issue with regard to public education, it is not with regard to sensationalising the ‘alleged’ uselessness of damp meters because in fact, they are far from useless and form an important checkpoint in any professional damp investigation. A professional site practitioner would know this. It is old news to say that these instruments have their limitations and can’t be used in isolation to diagnose rising damp, every professional practitioner should also know this.

The lowdown on calcium carbide testing

Calcium Carbide is a critical & accurate site test

Calcium Carbide is a critical & accurate site test

We next arrive at another wrong that needs to be corrected… I have spoken to a number of damp ‘specialists’ who do not believe that calcium carbide testing forms any useful part of a site damp investigation process. I have also seen this viewpoint in print and this is taught on the back of three falsehoods:

  1. Calcium carbide can not be used to measure total moisture content (TMC), rather it can only measure capillary moisture content (CMC), which is meaningless.
  2. Calcium carbide testing is not accurate enough or  less accurate than gravimetric (Oven drying) testing.
  3. Calcium Carbide testing is too ‘invasive’ and not suitable under most survey circumstances.

As with lots of industries we can often make the mistake of assuming that trade bodies are industry regulators when of course they are not. They are there to promote the interests of their members and in turn generate income for themselves. If a trade body were to promote the truth, which is that calcium carbide is a valuable tool in the diagnostic process, then the incredibly high incidence of incorrect diagnosis for rising damp would be quickly addressed. Of course, this would immediately mean that the damp industry would need to shrink to a fraction of its current size, because as I consistently say, rising damp is incredibly rare. The damp proofing Industry body generally promote the viewpoint that rising damp can be diagnosed with a visual inspection, a moisture meter and ‘common sense.’ Since common sense isn’t all that common we prefer to adopt the academically accepted view that in fact moisture meters can not be used in isolation to diagnose rising damp, no matter how much common sense the user has.  Ironically, where I do find rising damp, it is generally ‘induced’ rising damp caused by inappropriate damp proofing works.

I’ll deal with each of these three points relating to calcium carbide testing in turn:

  1. Calcium carbide can in fact be used to measure total moisture content (TMC) but I quickly found out that the academic process used to determine TMC is long winded and diagnostically insignificant. The idea here is that TMC can only be arrived at after first understanding capillary and hygroscopic moisture content in the wall being tested. The simple formula is CMC-HMC = TMC            Surprisingly, masonry walls have a low vapour resistance of around 7, to help contextualise this, loose fibre insulation has a VR of 1.  What this means is that internal masonry walls will naturally absorb some moisture from the atmosphere and and reach a level of moisture equilibrium with the internal environment. This absorbed moisture is the natural hygroscopic moisture content (HMC) within that wall. The HMC is generally very low, in fact, usually so low as to give a zero reading when tested with calcium carbide. We have never yet, in hundreds of damp surveys found a HMC that was at significant levels that would affect the survey outcome or the final conclusions and recommendations for work. To establish HMC, you would simply find a dry area of wall using your electronic moisture meter in scan mode. Despite them being referred to as ‘salt’ meters, in fact they are excellent for determining where damp is absent rather when where it is present. Once you have scanned a dry area, test this area with calcium carbide and that gives you your HMC. If you don’t yet agree that HMC is an insignificant part of the process for determining total moisture content then try it for yourself over the course of a few surveys. That being said, if I am doing expert witness work, then I test for HMC because this is the academically accepted process. It is simply a pointless exercise for the vast majority of damp investigations.
  2. As with all damp investigations interpretation of your results is critical. If you get a high capillary moisture content of 3% at wall base and it has caused decorative spoiling then you need to take action. This is despite the fact that BRE 245 tells us that 5% is the accepted level at which remedial action may be required. Of course if I ran a laboratory that carried out gravimetric testing of masonry samples then I might also promote the idea that oven drying is the only acceptable method for testing total moisture content but it simply isn’t true. Even BS5250, which is the COP for the management of condensation in buildings promotes calcium carbide as being almost as accurate as oven drying. In my opinion, oven drying is unnecessarily time consuming, expensive, and will provide results that are diagnostically insignificant when compared to tests results obtained with calcium carbide. Ironically, oven drying isn’t a method we see used by the damp industry, they generally do no diagnostic work but cite the superiority of oven drying over calcium carbide as an excuse for not doing either test. However, to the damp industry, diagnostic results are irrelevant since they generally deal in management solutions and not cures. In other words, they want to sell you waterproof plastering systems and chemicals, so if your only interest is in selling products that hide rather than cure the damp then why bother doing diagnostic work?
  3. If we carry out calcium carbide testing then the it is usually because we have decorative spoiling and remedial works are already required to the wall being tested. There is therefore no significant issue with drilling a wall and we have only had one resident refuse or not want invasive testing over the last ten years. That was simply because they were ill and didn’t want the noise of the drill. The only other reason we would carry out CC testing is where the wall appears sound and unspoilt and despite recording low surface readings for damp, we obtain very high scan readings for moisture at depth. Other visual evidence might indicate that waterproof plasters have been applied by the damp industry and we suspect a damp underlying wall dammed in with renovation plasters. In these circumstances we have an obligation to inform homeowners that their damp has simply been temporarily hidden rather than cured.  Screen Shot 2015-09-26 at 11.48.13The idea that calcium carbide testing is too ‘invasive’ is an idea heavily supported by Oxley & Gobert in their book, Dampness in Buildings. This isn’t a book I’d recommend, it contains a great deal of inaccuracy and biased opinion  and perhaps the fact that Gobert is Honarary Life President of Protimeter Plc has some impact on the only  published dissenting view I have found with regards to the otherwise generalised opinion that calcium carbide testing is an excellent site diagnostic tool. Worryingly, this book is heavily marketed by most firms who sell surveying equipment but it is outdated and technically incorrect in a number of areas. Good damp investigation is about having good process, a good range of diagnostic tools a a strong knowledge of building technology and a thorough understanding of the principles of damp investigation.

 

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