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    HSE call for design decisions justified by “risk rather than cost”

    An Open Letter from the HSE to the ‘structural timber industry’ has been published (29/10).

    The letter is intended for “all parties involved in the design, specification, procurement and construction of timber frame structures” explaining HSE expectations in relation to the management of fire risks prior to and during the construction of timber frame structures.

    The Structural Timber Association (STA), which represents the industry’s manufacturers and suppliers, has cooperated with HSE in producing the letter.

    HSE approach to off-site fire risks

    Fire precautions during the construction of timber frame structures fall within HSE remit. See the HSE published guidance on  Fire Safety in Construction.

    The regulator points out that duty holders have responsibility to ensure the safety and health of workers and those who might be affected by their work activities, including those arising from fire risks. Serious incidents have arisen where fires involving timber frame structures under construction have affected neighbouring buildings and HSE has therefore worked with the STA to produce the guidance.

    In summary HSE state:

    “All those making design and procurement decisions that significantly affect fire risk should consider and reduce the risk and consequences of fire during the construction phase through DESIGN. Failure so to do may constitute a material breach for which HSE will apply its Fee for Intervention scheme to those duty holders who have contributed to the breach.”

    Justify decisions in terms of risk rather than cost

    HSE state that CDM 2007 Regulation 11 requires risks to be considered and eliminated/reduced so far as is reasonably practicable through the design process adding:

    “The primary legal responsibility for assessing off-site fire risk rests with those making design and procurement decisions before work starts on site. Designers and manufacturers of timber frame structures duties under CDM Regulation 11 cannot be passed on to the Principal Contractor.

    The STA publication Design guide to separating distances during construction is intended to be used at the design and procurement stages of a project. HSE commends the STA for the substantial work carried out and make it freely available to all rather than being restricted to STA members.

    Following the guidance is “not compulsory” and if an alternative approach to the guidance is used, a competent person with fire engineering qualifications and experience will need to determine the risks and to identify appropriate controls. HSE go on to state:

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

    Design process to be followed

    The letter states that for a proposed structure, the STA guidance enables minimum separation distances to be determined. Where space does not provide the separation distances required for a Category A structure, it provides guidance on selecting alternative timber frame structures to provide an adequate level of fire protection to neighbours during the construction phase.

    If a Category B or C structure or alternative fire engineered solution is needed, then it should be specified when the timber frame is being procured. Everyone in the supply chain has a responsibility to work towards this end. In practical terms HSE expects:

    • An assessment of the particular site and its constraints when the method of construction is being considered;
    • For timber-framed structures, assessment can be undertaken using STA’s ‘Design guide to separating distances during construction’;
    • The assessment should identify that where there is insufficient separation distance to allow a Category A structure, the appropriate level of Category B or C to match the site constraints (unless an alternative fire engineered solution is developed by a competent person) should be recommended;
    • The appropriate category frame should be specified to the manufacturers;
    • Timber frame manufacturers, including non-STA members have a significant role to play in ensuring appropriate specification and procurement of frames. Manufacturers should be advising their customers of the guidance and requirements. Use of the STA audit checklist may assist manufacturers in compiling records to demonstrate the steps they have taken to discharge their obligations under CDM Regulation 11 and record who has made specific decisions;
    • Any specific information and instructions that must be followed to guarantee the specified category or approved solution to be achieved on site must be passed to the Principal Contractor;
    • The Principal Contractor must adhere to the conditions required to achieve the specified category of structure; and
    • The Principal Contractor must devise and apply appropriate fire precautions during the build, including control of hot works, provision of fire warning and extinguishing systems, provision of means of escape etc.

    Finally the letter states:

    “HSE inspectors expect duty holders to comply with CDM Regulation 11 using this guidance to assist. Where a duty holder chooses not to follow the STA guidance but to implement a fire-engineered solution, standards of the equivalence to the guidance should be adopted.

    Duty holders should expect that in the latter circumstances, if lower standards are adopted then HSE may consider there to have been a material breach of health and safety law attracting charges under our Fee for Intervention Scheme”

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