<P> Between the cladding and the wall there is a cavity where rain can run down . In the event of a fire this draws hot air up like a chimney, intensifies the fire, and spreads it to the top of the clad area . The fire can then get inside the building through open windows, for example to curtains blowing through windows . </P> <P> In addition to the chimney effect, the cladding material itself can contribute to a fire . Brick has excellent fire resistance; planks or weatherboards made from fibre cement or steel have high fire resistance; aluminium and reconstituted timber products have good fire resistance, and timber weatherboards and plywood sheets have poor fire resistance . Composite cladding typically consists of panels 3--5 millimetres (0.12--0.20 in) thick made of a core material sandwiched between two aluminium faces . The core material may be polyethylene (which is combustible), a mineral - based material, or a combination of both . Panels of the same appearance may have different core materials; those with a higher proportion of mineral core withstand fire better, but can still be considered combustible . Fire will be spread by the cladding if the core is combustible . </P> <P> In the wake of the Grenfell Tower fire in London, and similar fires in France, Dubai, and elsewhere, great attention has been paid to the fire protection qualities of cladding used in tower - blocks and similar high - rise multiple - occupancy housing and, in particular, the use of aluminium composite material (ACM) and ACM panels (ACP). Grenfell Tower was clad with composite panels with a polyethylene core which is thought to have contributed to the fire; these panels cost about £ 2 less than ones with incombustible core . There are estimated to be about 600 high - rise blocks of flats in the UK that have "similar" cladding and some fire safety tests--not full BS 8414 tests--were carried out on panels; of the first 75 tested, 100% failed . </P> <P> Hardwood cladding is a solution for any wall, offering not just the cladding but all the detailed trims required to finish off the project and ensure a watertight result . </P>

The structure which is used to support a vertical cladding is known as