An open letter to the industry has warned that designers will be held responsible for ensuring timber frame designs fully take into account the close proximity of neighbouring buildings.

The HSE has acted in the wake of serious incidents where fires involving timber frame structures under construction have affected neighbouring buildings.

Already fire chiefs have warned that fires can rapidly overcome timber frame structures while under construction generating intense heat.

The main priority is then to ensure the fire does not spread to nearby buildings.

HSE head of construction sector & policy, Simon Longbottom, said: “Evidence from recent HSE inspections indicates that the risk of harm to occupants of neighbouring buildings from fire during the construction phase is not always effectively managed.”

He warns that the HSE has found that not all duty holders understand what is required of them.

The HSE said the primary legal responsibility for assessing off-site fire risk rests with those making design and procurement decisions before work starts on site.

Longbottom warns that designers and manufacturers of timber frame structures duties under CDM Regulation 11 cannot be passed on to the main contractor.

The letter adds that risk should be designed out as far as is reasonably practicable.

The principal contractor is obliged to consider and manage risks arising from the activities under their control at the site stage.

If an alternative approach to accepted industry guidance is used, a competent person with fire engineering qualifications and experience would need to determine the risks and to identify appropriate controls.

“The persons involved should justify their decisions and recommendations in terms of risk, rather than cost,” it reads.

Longbottom concluded: “Anyone in the supply chain who makes a decision, which significantly affects fire safety during construction, should be prepared to justify that decision.”

Mike Leonard, CEO of the Modern Masonry Alliance said: Construction worker safety must be paramount. Working at height in multi occupancy timber frame buildings under construction presents a clear risk.

“As a minimum there should be non combustible escape routes to allow safe evacuation but in reality as the recent fire at Nottingham University shows we need to call time on the use of timber for multi occupancy projects. This action will protect the lives and well-being of construction workers, residents and neighbours.

“This open letter from the HSE is welcome putting a clear duty of care on manufacturers, designers and contractors. It is important to act now to prevent any tragic loss of life.”