Grenfell Tower — Combustible ACM Cladding Defeated Every Compartment in the Building

Grenfell Tower, a 24-storey reinforced-concrete residential block in North Kensington, west London, burned out almost entirely in the early hours of 14 June 2017, killing 72 people in a fire that began in a single fourth-floor kitchen and reached the roof in roughly half an hour. The concrete frame never fell — and that is the point. The structure did exactly what a concrete tower is designed to do; the failure was in the skin that a 2015–2016 refurbishment had wrapped around it. A combustible aluminium composite material (ACM) rainscreen, with an unmodified polyethylene core, carried flame up and across the entire facade in minutes and defeated the building’s compartmentation completely.

This was not a structural collapse but a total compartmentation breach. Grenfell was built to the “stay put” principle: each flat is its own fire compartment, so a fire in one dwelling should be contained for long enough that the rest of the building can remain in place. That principle held for roughly fifteen minutes. The fire escaped Flat 16 through a uPVC window jamb into the newly installed external wall, found the polyethylene core of the cladding — a material with a heat of combustion comparable to petrol — and used the ventilated cavity behind the panels as a chimney. By 01:30 the fire had run to the crown of the tower; thereafter it spread back inward through dozens of flats at once, overwhelming the very compartmentation the stay-put strategy depended on.

The tower was completed in 1974 as part of the Lancaster West Estate. Its original concrete structure had no record of facade fire problems. The lethal change was retrofitted: an £8.6 million refurbishment, finished in 2016, that reclad the building in Arconic’s Reynobond PE panels over Celotex RS5000 polyisocyanurate insulation — a combustible system on a high-rise, where the product literature and the regulatory guidance pointed the other way.

The Grenfell Tower Inquiry, chaired by Sir Martin Moore-Bick, did not treat the disaster as an accident. Its Phase 1 report (October 2019) found the ACM cladding was the “principal reason” the flames spread and that the external wall did not comply with the functional requirement of the Building Regulations. Its Phase 2 report (September 2024) found 72 deaths that were “all avoidable,” the product of decades of failure by government and a construction-products industry marked by “systematic dishonesty.” Grenfell has become the global byword for what a combustible facade does to a fire-safe building: it converts a contained kitchen fire into a death trap.

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Lacrosse Tower, Melbourne — the Cigarette That Proved ACM Cladding Could Race Up a Facade

The Lacrosse apartment tower at 673-675 La Trobe Street, Docklands, Melbourne, was set alight in the early hours of 25 November 2014 when a discarded cigarette ignited a small balcony fire on the eighth floor — and that ordinary, survivable fire then ran up roughly thirteen storeys of the building’s exterior in minutes, reaching the roof above level 21 by 2:35 am. No one died and no one was seriously hurt, but the proximate cause of the near-catastrophe was not the cigarette. It was the cladding. The tower’s external walls were sheathed in aluminium composite material panels with a 100 per cent polyethylene core — a combustible plastic, calorifically comparable to diesel, sandwiched between two thin aluminium skins — and that core converted a localized balcony fire into a vertical facade conflagration.

This was Australia’s first major aluminium composite cladding fire, and it failed in the manner fire engineers had warned about for decades: the building’s internal compartmentation, the floor-by-floor separation meant to keep a fire in the unit where it started, was bypassed on the outside. The flame did not burn through the building; it climbed the skin of it, re-entering apartments through windows and balconies storey after storey while the concrete frame stood undamaged. The structure never approached collapse. What burned was the facade and the units it ignited, leaving the tower gutted along its exterior and forcing the night-time evacuation of roughly 400 to 500 residents.

The Lacrosse was completed in 2012, a conventional reinforced-concrete residential high-rise of no structural ambition. Its defining flaw was specified, not built into the bones: the design and construction chain approved and installed a cladding product, marketed as Alucobest, whose combustible core had never been tested to comply with the deemed-to-satisfy fire provisions of Australia’s building code for an external wall of that height.

The Metropolitan Fire Brigade’s post-incident report named the mechanism without euphemism — non-compliant combustible cladding drove the rapid external fire spread. Five years later, in February 2019, the Victorian Civil and Administrative Tribunal turned that finding into a landmark apportionment of legal blame, holding the builder liable but assigning 97 per cent of the responsibility down the chain to the fire engineer, the building surveyor and the architect. The Lacrosse became the case that proved, before Grenfell, what a polyethylene-cored panel does to a tall building: it makes the facade a fuse.

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