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October 24 2018 General
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Single Ply Versatility- Can create issues!
24/10/2018
BRUNTON’S BLOG: Single Ply Versatility- Can create issues!
The design flexibility and versatility possible with single ply roofing systems is almost endless. Although still often referred to as “new” technology in roof waterproofing, the fact is that we have single ply roofs installed in the UK for almost 40 years or even more and they are still performing. There is no doubt that single ply roofing has, in part, been responsible for enabling designers, principally architects, a freedom of expression in building design. The roof has become part of the aesthetic building concept on many occasions providing some buildings with award winning capability that otherwise would not have merited consideration for any shortlisting. Any review of aesthetic building design in the modern era can surely identify buildings that have transformed the built environment because of their roof design and the visual impact it contributes to – urban as well as rural.
Single ply roofing provides the flexibility of ‘modern’ lightweight roof waterproofing membranes combined with a range of essential but also compatible accessories for correctly detailing the most complex of roof shapes. In some cases’ this is enhanced by adding colour or coping with structural movement without compromising the visual impact of the design. Adding engineering principals to the roof mat design with factors of safety of attachment systems and continued development in fastener and adhesive technologies further enhance the design possibilities of the single ply roof.
However, we know that the potential of single ply roofing systems can sometimes be compromised by many factors, including but not limited to; poor design, procurement, installation and aftercare.
At last week’s autumn Technical Committee meeting among many interesting topics and issues discussed was ensuring adequate kerb/verge detailing to perimeters and also correct structural support to timber decking specifically at board edges. This is necessary to ensure continuous support of the roof mat comprising of AVCL, insulation and single ply roofing membrane in a warm roof situation.
During subsequent discussion with one of our SPRA registered contractors they explained the type of situation that they came across that emphasises this point. As can be seen in the pictures below, a perimeter with low kerb height and finishing detail combined, in this case, with lack of adequate deck support caused deck flex under the weight of ponding water- bit of a vicious circle as further water leads to more deck flex and so on! This clearly can lead to water ingress into the building – a significant inconvenience to the client!
Despite the protestations of the installing roofing contractor at the time, the detail was constructed like this and only corrected some time later when it was clear water ingress was due to the issues described above. The correction at the perimeter entailed raising the kerb height, installing new adequately supported decking to create a positive back fall and then re-flashing the detail to the outside edge below the zinc counterflashing.
In fairness to all parties the roofing contractor was paid for carrying out the necessary remedial work but so much could have been saved in time, effort, money, reputation and stress levels of all concerned by better understanding and collaboration prior to commencement of work on site.
The construction industry continues to lack in this regard with so much correction or remedial work necessary that could have been avoided with better consultation.
Hopefully the current working groups formed as part of the IRG (Industry Response Group), WG1-WG12 will attempt to tease out these issues over the early part of 2019, as they can be culturally embedded, in order to ensure competence and better collaboration between all design and construction of buildings.
SPRA will now be represented on two of these working groups WG2-Installers and WG12-Products, to influence positively in this respect.
In summary while our single ply roofing systems can provide the designer with limitless options to create award designs no element of the supply chain can work in isolation. More collaboration of all in this chain will lead to better understanding enabling improved aesthetic design and increased building performance outcomes.
As always, your feedback is important and welcomed!
Ronan Brunton