What went wrong and why

September 1968

The collapse was due to an explosion at approximately 5.45am on 16 May 1968. The explosion blew out the non load-bearing face walls of the kitchen of flat 90 on the 18th floor and also the external load-bearing flank wall of the living room and bedroom of the flats, thus removing the support for the floor slabs on that corner of the 19th floor, which collapsed.

The flank wall and floors above this collapsed in turn and the weight and impact of the wall and floor slabs falling on the floors below caused a progressive collapse in this corner of the block right down to the level of the podium.

The tribunal concluded town gas was the source. This came from a leak caused by a faulty nut at the standpoint end of a piece of flexible hose linking a gas cooker to the gas supply, touched off by a lighted match from a tenant.

The cooker had been fitted by a neighbour who had no specialised training as a gas fitter. Nevertheless the tribunal “are satisfied that he acted in accordance with good practice and was in no way responsible for the subsequent explosion”. The type of nut has since been embargoed pending testing.

On the issue of system building the inquiry concluded that the problem of progressive collapse had not been considered by most structural engineers concerned

with the development of tall system-built blocks. In addition to Ronan Point it is probable that that a considerable number of other system-built blocks are susceptible to progressive collapse of a like nature.

Progressive collapse is not an inevitable feature of system-built blocks. It can be avoided by the introduction of sufficient steel reinforcements to give continuity at the joints, and the adoption of a plan form that provides for the arrangement of the load-bearing walls in such a way that the load is carried by alternative paths if part of the structure fails.

The report states: “The extent of the collapse subsequent to the explosion was inherent in the design of the building. The collapse has exposed a weakness in the design.” It added: “It appears to us that there has been a blind spot among many of those concerned with this type of construction and it would be wrong to place the blame on the designers alone. They fell victims to the belief that if a building complied with Building Regulations and codes of practice it must be deemed safe. Experience has shown otherwise.”

It noted: “In the broadest sense it could be noted that the two major professions concerned – architects and structural engineers – have been found wanting; the former for failing to call adequately upon the latter and the latter for failing to take much interest in system-building generally.”