Sunday, August 3, 2014

Who is managing build quality these days? – Part 2

Guest article from Joe Malone BSc(Hons) ICIOB

There is a particular shortcut that seems popular with contractors at the moment, which is installing windows using nothing more than expanding foam. No mechanical fixings whatsoever and sometimes even the additional external frame sealant is omitted; I have encountered this a number of times and it is completely unacceptable

In last week’s article Joe Malone provided a number of case studies which demonstrated how build quality does not appear to be adequately managed whilst building works are being undertaken.  The article raised a lot of interest and debate in numerous social media discussion forums and I have no doubt that the further case studies below will equally stimulate a similar level of interest:

Case Study 3: Make Sure the Finisher Goes Back

This particular case relates to a residential high-rise block in the centre of London. The block was converted to residential use and fully refurbished to a nice standard. Unfortunately the flats had suffered from water ingress from the day keys were handed to residents and a number of investigators had failed to get to the route of the problem. My investigation focused on one flat in particular because the resident had moved out until the problem was resolved. The flat was in disarray when I got there, carpets had been taken up and clearly there had been a serious attempt to uncover the source of the water ingress.  You may or may not know that many contractors employ trades people called finishers. These are the people who go in after a bathroom has been installed and silicone round the bath & windows etc., and carry out all those other minor finishing details. Hold that thought…

I immediately used a thermal imaging camera and it was fairly obvious that the water ingress appeared to be concentrated at the base of the patio doors that led to the balcony. Note the dark and lighter blue areas in figure 1 below. The dark blue areas were particularly telling as this was at the base of the doors. Also note the orange band sitting on top of the doorsill, this is the metal packing plate that can be seen in figure 2 below.

Fig 1. Damp areas to base of patio doors - Source: Author's Own
I noted a gap at the base of the aluminium patio doors and a steel packing plate, See fig 2 below, but I couldn’t be sure whether or not the doors had been sealed to the frame with a gasket that I couldn’t see, it seemed too incredible that the doors had not been sealed in their frames.  I decided that the only way to prove this issue was to remove the MDF patio doorsill inside the flat. With the sill removed I could see daylight between the patio doors and the doorframe. The doors had been levelled and adjusted with the steel packing plates seen in figure 2 below but no one had bothered externally sealing the doors in their frames. I checked other patio doors in the development and not one patio door had been sealed in the whole development. It seems quite simple doesn’t it but this problem had remained undiagnosed for almost ten years.

Fig 2 - Source: Author's Own
I do wonder how such a significant and ultimately damaging defect could have been missed. Did the contractor forget to send back the finisher or did they think that sealing with Polysulphide mastic wasn’t necessary due to the doors being partially protected from the elements by the balcony? I’ll never know the answer but I suspect it is yet another example of the contractor cutting corners on their work. This defect caused tens of thousands of pounds worth of damage to expensive laminate flooring and other internal fixtures. I see so many of this kind of defect that I will be keeping a regular blog on my own website (Link).

There is a particular shortcut that seems popular with contractors at the moment, which is installing windows using nothing more than expanding foam. No mechanical fixings whatsoever and sometimes even the additional external frame sealant is omitted; I have encountered this a number of times and it is completely unacceptable.

In the meantime if you are considering trusting build quality to the contractor, your building control officer or the NHBC guarantee then I hope these case studies make you think again. Pursuing NHBC claims is a less than pleasant experience and of course they will always look for reasons not to pay out rather than to pay out. I could have cited many more similar examples.

Case Study 4: Sometimes even when it looks right it isn’t.

This particular issue relates to survey work I carried out on building within what was formerly a large industrial building constructed in the late Victorian (Circa 1890)  era, of London stock bricks. The building had been converted to residential cottages within a gated community by a large National developer in 2001 and yet the properties were suffering from severe wall base damp and decorative spoiling.  There were far too many defects to note here but one that I did find interesting relates to the installation of a retrofit concrete floor slab within the property.  I first noted a very obvious problem in that the blue plastic Damp Proof Membrane (DPM) was simply turned up the wall and not connected to any Damp Proof Course (DPC) in the wall. Since the wall was absent of a DPC then how could it be? In any event if there was a DPC present then achieving an effective link between the DPM and DPC is virtually impossible. This is one of the reasons you should never fit retrofit concrete floor slabs in old properties. See fig 3 below.

Fig 3. Blue plastic DPM for concrete floor slab turned up the walls - Source - Author's Own 
For some reason I decided to check the gauge of the plastic DPM that had been installed with a micrometer. It simply did not feel substantial enough when compared to 1200 gauge DPM that I had previously handled. I took a small sample from the edge and found that the constructor had installed cheap 800 gauge builder’s plastic. See fig 4 below. Remember, this was a very expensive residential development in the centre of London.

Fig 4. Micrometer proved that 800 gauge builders plastic had been installed - Source - Author's Own
I would expect 1000 gauge as a minimum for DPM and suspect that 1200 gauge was actually specified. Corners were clearly cut despite 800 gauge builders plastic not being fit for purpose as a DPM. It will be prone to puncturing due to a lack of durability and I suspect was probably damaged during installation. A constructor who cuts corners in this way is not going to take care during the DPM installation process. Incidentally, in case you’re wondering about the margin of error for the micrometer, I folded the piece of DPM several times to overcome the small margin of error specified by the manufacturer.

Joe Malone BSc(Hons)ICIOB
Malone Associates Ltd

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