Following the Grenfell tower fire disaster I was asked to make an assessment of three tall blocks of residential accommodation in Greenwich. Three different cladding systems had been installed and the installer was no longer trading. I had access to BRE fire test reports (BS 8414-1) on some of the systems. I also had access to a fire safety strategy report for the buildings and some detail drawings recd from the main contractor. Some of the blocks were more than 18 m high and parts of the accommodation had sprinklers, others did not, which appeared strange. It was very difficult to establish the multi-layer construction behind the cladding face. One of the systems appeared to be acceptable according to a BS 8414–1 fire test report but I was not able to establish the exact construction detail and, more importantly, whether or not cavity barriers had been placed at each storey level as recommended. One of the systems involved brick slips adhered to polyurethane foam slabs and, although this assembly was acceptable under the BS 8414-1 regime, I was concerned about the missile hazard (to fire fighters and the public) of brick slips falling off the face of the building from great height. One of the systems involved a large thickness of combustible expanded polystyrene foam ‘protected’ by a glass fibre mesh/resin finish on the outside which again appeared acceptable under the BS 8414 test regime – the system did well despite the fact that expanded polystyrene foam is well known for its propensity to form flaming pools of molten droplets and masses of black smoke – it seems that the glass fibre mesh forms a protective cloak over the foam suppressing fire spread for a time (while the mesh remains in place).
Another of the cladding systems relied upon polyurethane adhesive to hold large heavy 8mm thick panels in place and there did not appear to be data supporting the use of the adhesive when heated above150 degC by jetting flames out of a window and associated thermal radiation (the only data I was able to obtain was ‘a service life of 150degC for 1hr’).
Because of uncertainty over the actual construction installed, it being hidden from view, I had little choice, in view of the internal and external fire hazard, but to recommend installation of residential sprinklers. However I pointed out that sprinklers inside the building would not necessarily prevent a fire on a balcony outside the building from attacking the cladding. A fire in a car parked close to the cladding would also be a hazard. I prepared a 12-point list of concerns and solutions.
Unlike the Grenfell tower single stair plan layout the escape routes in the Greenwich building would be mainly unaffected by a cladding fire.
Client: a property management company.
