Rare Timber Framed House

Timber Framed and Technically Obsolete.

Rare 1940’s Timber Framed Building

I was asked to carry out a survey on a fascinating building this week, a very rare 8 bedroomed timber framed building. I’m told that there are only two of these buildings remaining in the whole of the UK so its highly likely that I won’t see another one and most  of us won’t see one of these buildings in our whole career. The building remains largely unchanged from the day it was built.

The building currently has a wall U-Value of around 2.1 W/m2K which is as bad as you’re likely to find and well below the current UK building regulations requirement for 0.16 W/m2K. There is no functional central heating system installed and residents gain what little warmth they have from an AGA in the kitchen, which is where they spend most of their time. It’s fair to say that they are built of sterner stuff than most of us, myself included.

Failed Hip Shingles

You won’t find any reference to this particular building in BR282, ‘Timber frame housing 1920–1975: inspection and assessment.’ The building was constructed in 1941 when masonry construction was the norm but I think there was a need for rapid construction and anecdotally I’m told that the building was used as accommodation for land girls during WWII.

Most timber buldings constructed at this time were platform framed but we’d need a more invasive inspection to confirm the exact method of construction.  We think that this is post and beam construction, or a structural frame of widely spaced timber posts with infill studwork set between the sole plate and wall plate. Joisted  and planked flooring and  4″ x 2″ rafters fixed to the wall plates at 400mm centres. Roof battens are 3″ x 1″ and closely centred to allow for a large headlap to the cedar shingles, because the roof has no sarking membrane installed. The internal walls are clad with plasterboard, which came into common use during the 1930’s.

OLYMPUS DIGITAL CAMERA

Closely centred roof battens allow for a large shingle headlap

 The building’s timber frame is built off traditional brick footings, to which a timber sole plate is attached, the timber frame is then built off the sole plate. There should be a physical damp proof course between the brick footings and the sole plate and indeed, the timber sole plate can be weak spot in these buildings as they are subject to timber decay. For a full assessment of these buildings the sole plate and the base of the timber posts should be opened up for inspection. However, for a timber framed building approaching 75 years old this in in remarkably good condition and serves as an interesting historical marker with regard to the need for rapid construction in the 1940’s.

 

 

Typical Directly Clad Stud Timber Frame

 

The walls of our building have  4″ timber studding at 400mm centres  that is externally sheathed with timber, however where the technical detail differs from the image is that this building has no insulation installed and rather than external timber boarding, this buildings is clad with cedar shingles. The roof is also clad with timber shingles. Whilst the technical details are interesting, the very obvious problem is that this building is technically obsolete and can not provide the level of thermal comfort required for modern living.  In fact, there is an oil fired central heating system installed but heat losses were so great in the building that once the system failed, the occupants had no interest in getting it repaired due to the high cost of heating the building. Unsurprisingly, the occupants tell us that the building is incredibly hot in the summer and incredibly cold in the winter.

OLYMPUS DIGITAL CAMERA

Shingle clad chimneystack

We understand the need to retain the external appearance of this building and we see no reason why this building should not provide accommodation for another 75 years, however, to achieve that aim, a substantial upgrade in thermal insulation is required, either internal wall insulation (IWI) or external wall insulation (EWI). Installing IWI, using something like 93mm Gyproc Thermaline would future proof this property without affecting the external aesthetic appearance but there would be a loss of internal floorspace, not a particular concern in a property of this size, however, this would involve major upheaval for the occupants and would also not deal with another concern relating to poor security. You’d gain entry into this property within two minutes with a decent battery powered circular saw.

OLYMPUS DIGITAL CAMERA

Cedar shingles can be retained.

Our preference would be to remove and store the cedar shingles and clad externally with a structural external wall insulation (SEWI) system, Structherm or similar,  the building lends itself very well to this approach since it has a wide soffit detail. The SEWI could then be over clad with the existing cedar shingles and the aesthetic appearance would be retained bar the fact that windows would be noticeably set back, a feature that would afford better weather protection. Whatever approach is adopted, this is a fascinating building that thoroughly deserves a new lease of life.

 

Please follow and recommend our blog page:

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.

Please follow and recommend our blog page:

Structural Assessment of Freestanding Walls

Sliding into Danger

Freestanding Wall & Zip Slide

We’ve had to assess structural integrity of two freestanding walls recently, the first was relatively straightforward and involved a resident who reversed their car into the boundary wall surrounding his apartment block. The client wanted to know whether the wall was safe in its damaged condition. Since it was also a retaining wall and damage fell outside of acceptable limits, we recommended that it was taken down and rebuilt. It was a very easy & objective decision based on information outlined in BRE Good Building Guide GBG 13.

The second was a little more unusual and called for a more urgent and subjective opinion. As a surveyor, there are often grey areas that call for professional opinion. In this particular case we noted damage to a 2m high rendered free standing wall, it had failed at its junction with the corner of the main building and also had a long horizontal crack at a bed joint. Both the leaning wall and the degree of cracking are easy issues to assess but what made this assessment unusual was the installation of a large zip slide to the rear garden that ended at the garden wall. The steel support post was installed just beyond the garden wall. In fact the damaged render tended to indicate that that users of this feature were hitting the wall hard with the base of their feet as the zip slide came to a stop. Now you might expect that hitting the wall would cause it to lean away from the zip slide but in fact it had the opposite effect. Impacting against the wall caused failure along a slip plane near the wall base, 4 courses up from the floor. Essentially, there was almost  a complete horizontal fracture of the mortar bed joint.  Impacting against the wall appears to have caused counter rotation at the top of the wall so that it leaned towards the zip slide button seat rather than away from it.

Extract from BRE GBG13

You’ll see by the extract taken from BRE GBG13 that a decision to take down and rebuild was fairly straightforward since the wall in question had a full width horizontal crack exceeding 600mm in length. The lean was within acceptable limits.

OLYMPUS DIGITAL CAMERA

Horizontal failure across the mortar bed joint.

OLYMPUS DIGITAL CAMERA

Fracture at Junction with Main Building

Where the matter becomes complicated is when assessing whether the wall presents any immediate danger to the occupants or general public that facilitates the requirement for immediate taking down to make safe. Had the zip slide not been present then we were satisfied that this wall presented no immediate danger but  the structurally unsound wall and a zip slide installation were a dangerous combination and we advised the occupants to not use the zip slide and further advised our client that the wall needed immediately taking down and rebuilding. Digging up and re-siting the steel support post for the zip slide so it is planted in front of, rather than behind, the rebuilt garden wall may prevent re-occurrence of future impact damage.

 

 

 

 

 

 

 

Please follow and recommend our blog page:

Cutting Corners – Builder Short Cuts

A Number of Builder Short Cuts Adopted by Builders

Builder Short Cuts – We come across so many short cuts adopted by builders that I thought I’d start a regular post highlighting some of the strange decisions made by site trades people to save on time or money. As you’ll see, some of the decisions taken make no sense whatsoever. See for yourself.

Short Cuts 1

New consumer unit

New consumer unit

Why not use the circuit labels supplied?

New Ground Spike

New Ground Spike

Laid directly over the patio as a trip hazard.

Need a matching slate?

Need a matching slate?

This will do fine!

Need to remove downpipe?

Need to remove downpipe?

No need, just render around it.

Use of plumbers mate to stop leak

Use of plumbers mate to stop leak

Quicker to tighten unions on valve?

Need a roof vent?

Need a roof vent?

Just hide duct behind rafter.

Need another roof vent?

Need another roof vent?

Just hide duct behind rafter.

Double glazing in timber frame

Double glazing in timber frame

Needs installing on glazing bars.

Installed drains in wrong place?

Installed drains in wrong place?

Just grind a hole in your Aco channel.

Not maximising access costs

Not maximising access costs

Ignoring other defects is not smart.

No frost protection on condensate

No frost protection on condensate

A critical omission

Need a newel post fixing kit?

Need a newel post fixing kit?

Just nail them on!

 

Please follow and recommend our blog page:

A Case of Pillowing or Mattressing? – EWI Failure

A Brief Explanation of Failure Modes in External Wall Insulation Systems

Screen Shot 2015-10-11 at 20.05.42We were recently asked to look at an EWI failure for a potential client. This was a homeowner who had spent £15k on having their home externally refurbished with an EWI system. At circa £100 per square meter this was an expensive system but they’d done their homework and were happy to pay a little extra because they believed that they were buying the best. I was more than a little alarmed when they explained that the system had been installed in 4.5 days and indeed, this did not align with  the 3 week programme that had been described by the installer.

Thankfully the  homeowner had taken photo’s throughout each stage of the installation and this made it easier to understand exactly what had gone wrong, even ahead of doing any invasive site investigation work. Our understanding is that within days of the installation being completed the homeowner noticed that the underlying EPS insulation boards could be seen through the finished coat of decorative render. This was initially noticed at night when the external uplighters shone against the render but as the days went by the boards also became clearly visible during the daytime.

The system designer looked at the problem and described ‘pillowing’ in the EWI system though no explanation for this phenomena was presented. Their proposed remedy was to strip off the render back to the EPS boards and to re-apply the base coat, mesh and finished render; a proposal that we do not feel will go close to addressing the problems on this installation.

In fact, we didn’t agree that this was pillowing but we can understand why the term was used since the insulation boards can also be seen under the finished render when either pillowing or mattressing occurs.  Both effects are generally linked to poor adhesion when the board is bonded to the substrate unevenly across its surface,  for mechanically insulation fixed boards the same effect could also occur where the recommended fixing pattern has not been followed.  We recently encountered an installer who fully bonded phenolic boards to counteract board shrinkage but we’re not aware of any evidence proving this proposition and our view is that it will have little or no effect on the problems caused by board shrinkage, our solution to this problem is not to specify Phenolic boards.

Whether you see pillowing or mattressing can depend on external temperatures and pillowing is linked to warm temperatures, whilst mattressing is linked to cooler temperatures.  The amount of adhesive recommended varies from system to system and for this system a minimum coverage of 40% was recommended.  There is a slight anomaly here since generally you should avoid voids between the insulation and substrate to prevent a stack or chimney effect, this is a naturally induced vertical flow of air that is to be avoided in these systems.

Poorly Installed EWIS

IMAG1882

Poorly jointed EPS

20150708_172146

Insufficient base coat application

20150708_173127

Exposed edge bead

20150708_172320

Poor coverage to reinforcing mesh

20150708_173526

Bead prior to decorative coat application

20150708_172919

Mesh prior to decorative coat application

20150708_172344

Poorly trowelled base coat

20150708_172649

Poorly trowelled base coat

20150708_172344

Poorly trowelled base coat

Screen Shot 2015-10-11 at 21.27.28

EPS boards visible under decorative coat

Screen Shot 2015-10-11 at 21.26.57

EPS boards visible under decorative coat

Screen Shot 2015-10-11 at 21.48.38

EPS boards visible under decorative coat

Screen Shot 2015-10-11 at 21.49.04

EPS boards visible under decorative coat

IMAG1878

Poorly installed EPS

IMAG1870

Poorly installed EPS

IMAG1877

Poorly installed EPS

IMAG1835

Uninsulated reveals

IMAG1876

Poorly applied corner bead

IMAG1841

Poorly jointed EPS

IMAG1885

Timber pattressing and poorly jointed EPS

IMAG1888

Timber pattressing and poorly jointed EPS

IMAG2046-2

Failed sealant 8 weeks after installation

Interestingly, in this particular case, the system designer ordered some 20mm thick insulation boards that we understand were to be used to level off the substrate but they were never used by the installer. Once the EPS boards were installed they should present a  ‘smooth in-plane finished surface’, any high spots should be rasped or sanded to achieve this if required. The installers mentioned to the homeowner that they were short of base coat but when questioned as to why they hadn’t ordered more, said that they’d ‘managed’ with what they had.  Clearly they didn’t because the the mesh should be free of wrinkles and fully embedded in the base coat with the mesh pattern just visible on the finished surface. The system  logo should not be visible through the cured reinforcing coat and yet it was clearly visible. The manufacturer of this system also states that supplementary mechanical fixings are used with the adhesive insulation systems, especially during the strength development phase of the adhesive curing and yet supplementary fixings were only partially used for reasons we cannot fully understand. You will see from the image slider that the insulation boards are clearly visible in the finished EWI system and it is our belief that the reason for this is simply down to the fact that the base coat was too thinly applied to fully cover the underlying EPS boards. The effect got progressively worse in the days following installation due to shrinkage in the  base coat and decorative coat as it fully dried after the installer left site. They may have applied the term ‘pillowing’ as a generalised term to describe a situation where the underlying boards could be seen but as we said, we do not believe this is the technically correct description. The standard of installation is so bad on this particular property that we don’t believe that the three foreign sub-contractors who installed this system were certified installers, site communication was very poor due to language issues and they certainly weren’t managed during the process. However, we don’t want to mention the particular system that was used because we think this is probably irrelevant at this point. It is yet another perfectly good EWI system that has very poor site specific design and installation.

We have an update to this particular tale… 2 weeks after writing this blog and approximately 6 weeks after installation the system has developed its first moisture blister, we expect this to be the first of many but we’ll continue to monitor whilst the system designer provides a second technical report into the alleged reasons for failure. For some reason the first technical report was never made available and will never see the light of day though I suspect that may be due to our involvement.  We’ve inserted two images, one of the area where failure has occurred prior to application of the reinforcing mesh and topcoat and another of the finished render showing the moisture blister.

IMAG2081

Moisture blister near base of downpipe. Note terrible edge detailing on render.

Note poor detailing at base supporting rail

Please follow and recommend our blog page:

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.

 

Please follow and recommend our blog page:

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.

 

 

Please follow and recommend our blog page:

A Tale of Two EWI Failures – EWI Case Studies

Lessons Learned from Two High profile EWI Failures

We have been monitoring outcomes for quite some time on a number of  high profile external wall insulation system failures; all of which occurred on high rise blocks in Bootle, Wigan & Glasgow. We have reviewed the Wigan failure and have a clear picture as to why the render system failed at Scholes Village but we cannot yet share this information.

The failure at Stanley House in Bootle has I believe now been rectified but the cause of the failure was never published and we believe that the clients (One Vision Housing) even signed a gagging order as part of the court settlement. You can see evidence of that failure in the next video clip.

Stanley House EWI Failure

Whilst doing continued research on EWI failures we came across commentary relating to the Stanley House failure that has been published by one of the consultants involved in the failure.

Screen Shot 2015-09-28 at 08.45.04

After the initial gagging of information it is good to see that a clear picture has now emerged with regard to the cause of this failure; however it has taken  years for this information to emerge. The failure mode is unsurprising to us but begs the question as to who was monitoring the quality of this work on site? Missing metal cladding fixings are a very easy thing to spot  and correct, even to the least discerning eye. There was an immediate and urgent need to install a mild steel mesh around 6 buildings but we are unsure if this was installed as a temporary or permanent measure. There are some forms of insulation such as phenolic, that once wet need to be removed from the building. It will be interesting as we move forward to see if there are attempts to reinstate or repair  failed and saturated EWI systems. Some systems such as those containing XPS insulation will present greater flexibility for repair and re-instatement than others.

Screen Shot 2015-10-01 at 13.10.47

Another EWI Scheme with Insufficient Fixings

We next come to a case that has always been incredibly difficult to uncover information about… GHA’s Mini-Multi blocks. These blocks experienced failure very early after completion in 2010 and we saw reports of ‘extensive blistering’ in a number of blocks. The main contractor, ROK, went bust but they were not the EWI installer and we are unsure who ultimately footed the bill for remedial works.

The consultant dealing with this also published some recent findings with regard to these failures and we believe that remedial works are now complete; however we have to say that we find their reported reasons for failure as a little unusual.  The consultant stated that ‘The render on GHA high rise blocks had started to blister. The failure was identified as being due to a lack of water permeability in the topcoat.’  This directly contradicts information given to GHA residents by GHA representative, Ian Duff, who stated that ‘moisture and evaporation got in behind the over cladding.’  We are unsure if it ‘got in’ through failed building joints or whether wet insulation was installed but for either eventuality, no amount of permeability in the topcoat was going to lose this moisture through an evaporative process.

Screen Shot 2015-10-01 at 13.23.30

GHA’s Repaired Mini-Multi Blocks

The idea that these systems absorb moisture by the ‘overcoat’ principle is simply wrong and if they take in water through failed building joints or if wet insulation has been installed due to poor site storage facilities then the render coat is not designed to lose this moisture by permeability or breathability. These are weatherproof systems and water ingress will usually write off the affected underlying insulation. We always believed that such premature failure and blistering was a sign that the insulation was wet when installed but we are now even seeing systems installed with no sealant at all around windows and other critical junction details and these critical omissions would also be responsible for such rapid system failure.

There are two critical lessons to be learned from both these failures:

  1. Clients must have a robust and independent system in place for the quality management of works.
  2. Clients must understand their specification &  the terms of their BBA approval to ensure that there is no diversion from the agreed specification.

 

Postscript

An interesting discussion developed after this blog was posted with regard to the GHA EWI failures. Two separate interested parties told me that occupancy issues were believed to be a factor in these failures. The logic behind this is that the flats had a high number of  ‘stay at home’ occupants, possibly retired or unemployed. Therefore flats experienced a higher than average level of relative humidity, which permeated through the walls into the EWI system insulation. This is an interesting theory but given the rapid system failure it is not one that I think holds a great deal of validity. Moreover, if occupancy issues are a significant risk factor for EWI failure then you would need to complete a condensation risk assessment  for every project during the design process. (This does not mean a risk assessment for interstitial condensation, which is something I’d expect to see done on every project anyway)

In theory, it is a reasonable proposition and of course we know that EWI should not be installed on wet walls because evaporative moisture can  and does cause significant problems. However, there is no need to hypothesise about this potential factor since internal data logging can easily monitor and record internal environmental conditions, thereby providing a complete picture with to regard occupancy issues. Secondly, hygroscopic moisture content (HMC) and capillary moisture content (CMC) can also be checked and recorded in the building fabric to check if internal relative humidity is in fact having a significant impact on total moisture content within the building fabric. If the building fabric is dry then occupancy issues are not a significant factor.

 

Please follow and recommend our blog page: