Combustible Cladding Remediation in Practice

About this course.

Combustible cladding is dangerous because it can turn the external wall of a building into a vertical pathway for fire, allowing flames to climb the outside of a structure far faster than a building's fire-safety systems were ever designed to cope with. The most notorious products are certain aluminium composite panels (ACPs) with a polyethylene core and some expanded polymer insulation products. When the combustible core or product ignites, it can burn intensely and carry fire rapidly up, across and even back into a building through windows and openings, defeating the assumption that a fire will stay largely within the compartment where it started. Remediation has been necessary in Australia because large numbers of existing buildings were clad in these products before the risk was widely understood and acted upon.

To understand the hazard, it helps to picture how these products are made. A typical combustible ACP is a sandwich: two thin sheets of aluminium bonded to a core. Where that core is largely polyethylene — essentially a solid plastic — the panel contains a substantial quantity of fuel, even though its outer faces look like ordinary metal. Under normal conditions the aluminium skins hide the core completely, which is one reason the problem was not obvious from the ground for many years. In a fire, however, the aluminium skins can soften, buckle and peel away, exposing the plastic core, which then melts, drips and burns. Some expanded polymer products used for insulation or decorative facade elements behave in a related way: they are lightweight, organic and readily combustible unless adequately protected.