According to an official inquiry into the Grenfell Tower fire, the building did not adhere to building regulations in the wake of a major refurbishment that took place in 2015-2016.

Says the 1,000-page report, released by Martin Moore-Bick, insulation, cladding and decorative fins were added to the structure during its refurbishment that rendered it noncompliant with the UK’s Building Act 1984 and Building Regulations 2010.

The report states that compelling evidence exists that the exterior walls of the building did not comply with Requirement B4(1) of Schedule 1 to the Building Regulations 2010; saying, more specifically, that the walls promoted the spread of fire in regard to the height, use and position of the building.

The Building Act 1984 and the Building Regulations 2010 state that exterior walls should be capable of resisting the spread of fire, and alterations made to standing buildings should not influence the building’s compliance.

When the building underwent renovations from 2015-2016, aluminium composite material (ACM) rainscreen panels consisting of a polyethylene core and insulation panels made from polyisocyanurate (PIR) foam were employed to build a new outside wall surrounding the standing reinforced concrete walls.

Experts have found that on 14 June, 2017, when fire passed through Grenfell Tower, it probably reached the cladding by way of a hole which formed when hot smoke produced by a refrigerator fire prompted the deformity of the uPVC window jamb. The fire then extended to the combustible insulation materials surrounding the window frame before extending to the ACM panels.

PIR and phenolic foam contained within insulation boards found behind the cladding also contributed to the fire’s rate and spread.

The fire was made more intense by the presence of exposed polyethylene in the decorative crown topping the tower, which melted and dripped during burning, sparking more flames to strike further down the structure, which then spread back upwards. The fire then extended through the building until reaching the interior.

Fins of cladding had been built into the precast concrete crown for aesthetic reasons. Expert witness architecture professor Luke Bisby asserts that these prompted the crown to act in the manner of a “linear fuse” for the fire, spreading it in a horizontal direction. 

The report says that gaps were purposely left between the new wall of cladding and insulation and the concrete wall to promote ventilation and combat moisture. However, these gaps enabled the fire to spread with ease to the cladding.

While cavity barriers with fire prevention strips had been installed, they were fitted in a poor manner and not airtight. Experts say that if these barriers had been installed in a proper manner, there wasn’t much they could do to stop the fire once it extended to the ACM panels.