The tests that make sure tower blocks are safe

SIR – Bryan Bishop (Letters, June 26) asks why full-scale fire tests on cladding are not carried out nowadays.

Having been involved with external thermal insulation of buildings of all heights for more than 30 years, I can confirm that such tests are indeed carried out by the Building Research Establishment (now BRE). These tests are rigorous and successful results enable such products to be used on high buildings.

I have been told by fire experts that, even on buildings which have brick or concrete facades with no applied cladding, fire will spread upwards from apartment to apartment within 15 minutes, by which time the fire service should have arrived. The full-scale fire tests are designed to prove that the applied cladding material, even if it has some combustible components, does not accelerate the spread of fire. If the products used on Grenfell Tower had been subjected to such a test, they would never have passed.

It takes a few days to construct a full-scale fire test rig. If the materials include any wet-applied products, these must be left to cure for several days. I cannot believe that BRE is able to conduct proper tests of 100 cladding samples per day, unless these are basic combustibility tests that do not reflect the performance of the materials in situ. Iain Macdonald Kilmacolm, Renfrewshire

SIR – One of the scandals that will arise from the ashes of Grenfell Tower is that the local council will have known full well that many, if not most, of the flats were being sublet by the tenants, leading to hundreds more people living there than was officially acknowledged.

This practice, though pretty much universal across council properties in London, is usually ignored for reasons of expediency. A two- or threebedroom flat is typically sublet into three or four units with shared bathroom and kitchen facilities, and thus may be occupied by a dozen or more people. Geoff Ludlow Hythe, Kent