Guest article from Joe Malone BSc(Hons) ICIOB
'I have worked on a high number of complex building defect
investigations over the last 6 months and most of my conclusions have proven
that poor build quality and hidden latent defects are to blame'
My work as
a consultant building pathologist has led to me forming a strong view that
build quality simply isn’t adequately managed anymore. I have worked on a high
number of complex building defect investigations over the last 6 months and
most of my conclusions have proven that poor build quality and hidden latent
defects are to blame. Some might blame the demise of the traditional clerk of
works role to oversee build quality but I have formed a view that clients are
simply becoming too trusting. It costs money to run with a client side surveyor
and why bother when you’re working in ‘partnership’ or ‘collaboratively’ with your
contractor? They allow contractors to self manage build quality or they trust
to building control inspections and take further comfort in the fact that they
purchased an NHBC guarantee. You may
well be shocked at some of the things I encounter during my survey work so I
thought I would give you a flavor by way of sample of some case studies on recent survey
reports I carried out in London.
Case Study 1.
Overflowing with Defects
Fig 1. Balconies not
draining - Source: Authors Own
|
You will
notice the decorative spoiling to the underside of the balconies in figure 1.
The square steel stanchion you see is also the rainwater downpipe that the
balconies drain into. There is only one outlet for each balcony and the balcony
is covered with timber decking that sits above the asphalt coating on a Harmer
Uni-ring raised floor support system, as seen in figure 2 below. This was included in the build specification that I
managed to get hold of. It was rather a shame that the clients quality control
manager (if they had one) didn’t also get hold of it because then the client
might have seen that the system was completely omitted and replaced with larger
timber battens directly screw fixed through the bituthene membrane on the
balconies.
This
Harmer system was meant to provide a dual role:
1. To
raise the timber firrings off the balcony tray to allow rainwater crossflow to
the single balcony outlet.
2. To provide a fixing
system for the timber firrings, thereby preventing the bituthene membrane from
being punctured.
Fig 2. Harmer
Uni-ring system that was meant to be installed on balconies - Source:
|
Screw fixing
timbers directly through the bituthene membrane on the balconies was not a
sensible thing to do but the second issue was that solid lengths of timber
battens fixed to the floor meant that there was no crossflow of water to allow
it to reach the single drain point. The net result was that rainwater spills
over the edge of the balconies and tracks back underneath balcony ceilings
causing the decorative spoiling that can be seen in figure one. This
development is circa 10 years old and the problem has existed and remained undiagnosed from day
one. I am still staggered that the
developer managed to get away with this.
Case Study 2: The Lost Art of Parapet Walls
This case
proved two things, one, that the high cost of property does not guarantee a
better build quality and two, that no one seems to know how to build a
correctly detailed parapet wall anymore.
I was
appointed to investigate the cause of water ingress into a very expensive
residential block overlooking the Millennium Dome. Water ingress was affecting one
flat in particular below the top floor penthouse. As such most of investigation
work was focused on the top floor (See figure 3 below).
A
perimeter parapet wall surrounded the balcony and there were a couple of visual
tell tales that made me suspect that all was not well with the parapet.
1. No
visual sign of a dpc under the copings.
2. Cracked
mortar joints between copings
3. No
sign of weeps on either side of the parapet wall
4. Parapet
stone drips were compromised on the outer ledge by the installation of
fibreglass decorative cornice that was too wide for the application and
therefore covered the coping stone drips causing significant water staining on
the outer face of the parapet wall.
It was
obvious to me that a coping would need removing to fully inspect the parapet
and you can see in figure 4 below what I uncovered. This is as bad as it gets for
parapet wall detailing. The dpc was too narrow for application, it was sagging
into the cavity due to the lack of a hard support to bridge the cavity and
there was no effective cavity tray or drip details installed in the parapet. I
even found a couple of old joist hangers thrown into the cavity.
Fig 3. A good view from the penthouse balcony - Source - Authors Own |
Fig 4. A bad view from the penthouse balcony - Source - Authors Own |
You may be
able to see in figure 4 how the timber batten on the outer ledge compromises
the drip detail on the underside of the parapet coping stone. The fibreglass
decorative cornice was fixed to this.
I’ll let
you hypothesize what a very nice penthouse flat with this sort of view might
cost but it had no relationship to build quality, which was quite shocking.
In next week's article I will provide some further examples of poor building practice which could have been avoided if the build quality was managed more effectively.
Joe
Malone BSc(Hons)ICIOB
Malone Associates Ltd
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