Few fires shock the world....
Everyone knows about the Great Fire of London and depending on your age it may be that the Hindenburg airship disaster (one for my Mum) or Bradford Stadium fire is a vivid memory. Grenfell will certainly be remembered because of the huge loss of life and now there is Notre Dame.
Fortunately, no one was inside at the time (although a fire fighter was seriously injured fighting the blaze) but with such an iconic building the shock was palpable. I was in France at the time of the fire and the emotional tie of the building to the French was obvious.
Aside from the emotion, the Notre Dame fire was a classic example of what does and doesn’t burn with the thick stone walls surviving whereas the rest of the building (either timber or supported by timber) was largely destroyed. Brick and stone may lose strength in extreme fires but generally stays intact unless it is reliant on the support of timber or metal (which expands and buckles).
The French authorities said at the time that the whole building was within half an hour from being lost completely, but if you see the thickness of the walls, you do wonder if that was a bit of PR to say French fire fighters did a good job.
The insurance industry has been warning about the use of combustible materials for years, particularly in high-rise buildings. However, with developers under pressure to not only build more houses but make sure they are environmentally friendly, they understandably look for the cheapest alternatives. Unfortunately, these materials tend to be combustible and there are consequences when fires occur. Some combustible materials may be difficult to ignite and pass various fire safety tests, but once a serious fire develops, they will burn.
There is an irony that post-Grenfell we have the ongoing issue of removing dangerous combustible cladding from high-rise residential buildings, but at the same time new residential buildings (including high-rise) are being built of timber!
Cross laminated timber (CLT) is the latest material and involves gluing timber sheets together with the wood grain running in different directions to provide strength. It is generally made to have fire resistance of up to 90 minutes during which time it chars rather than burns completely, hence maintaining its structural integrity. However, I understand there has yet to be a major fire involving CLT and it has yet to be truly tested in a real-life fire. CLT has so far been used in buildings up to 9 storeys, but a plan for a 20-storey building was shelved when no insurer was found to insure it.
Fire testing is there to ensure that materials perform to a certain standard when fires occur and give adequate time for buildings to be evacuated, however, after Grenfell and the VW scandal, it is understandable that not everyone has complete faith in Government testing regimes. Let’s hope that they have got CLT right.