EXTERNAL WALL INSULATION: THE DEFECTS ARE OFTEN BUILT IN
External Wall Insulation Defects
Wherever possible we try to take the time to monitor ongoing external insulation schemes and we are currently monitoring two Midlands schemes to add to our knowledge base. The picture of the high rise block clearly shows that EWI defects are being built in and this is fairly obvious even to the casual passer-by. The insulation panels have been bonded with adhesive to the block but this does not mitigate for the reduction or complete omission of mechanical fixings. This is a high rise scheme and it is our opinion that premature failure is inevitable. The second scheme is a low rise scheme so on the upside, if things do go wrong then it is easier to inspect and access costs are not prohibitive for remedial works. However, this is a scheme using EPS insulation boards. We have to assume that the boards have been fixed with adhesive but again this does not mitigate for the lack of mechanical fixings; in this case only one fixing per board has been applied and there are no additional fixings around window and door openings. Generally these need to be placed at a maximum of 300mm centres around window and door openings.
We had a paper published in the Construction, Research and Innovation Journal in December 2013, entitled ‘The Risky Business of Covering Up.’ This paper heralds an early warning with regard to our belief that we will see a glut of external wall insulation failures, particularly on high rise blocks. These systems are often supposed to have a 30 years design life but very few clients will achieve these life spans unless they understand the requirements of their individual system BBA certification and stringently monitor site works to ensure that the BBA certification is being complied with. In our experience, there is often a complete failure to adhere to the BBA certified installation process.
EWI Installers are Getting Nervous
There was an extremely interesting development to this blog that I have been meaning to deal with… In fact I was contacted by the constructor concerned and requested to take the blog down. I’m not prepared to do that, it’s an academic blog that is aimed at continuous improvement so I do not feel that it serves the industry well to keep these issues hidden. The point I particularly wanted to deal with was the claim that pinnings to the insulation boards were only temporary and the intention was always to go back and install the required amount of hammer fixings once the adhesive had dried. Of course to try and confuse the issue with this claim is akin to admitting that you are putting the general public at risk… These systems are load and wind tested according to the number of hammer fixings installed and adhesive bond does not form part of the load test assessment. If a system insulation board is required to have 5 hammer fixings then this is required to satisfy structural adequacy. If you then claim that a reduced number of temporary fixings have been installed then you have actually installed a system that is structurally unsound (albeit temporarily) and at risk of falling from the building until the required number of permanent fixings are installed. I do hope that this is not a common approach for installing EWI but I really don’t believe it is since the process of installing ‘temporary’ pinnings would neither save time or serve any useful purpose.