Author: Lorna Johnson (Arup), on behalf of the Safety, Health and Wellbeing Panel
The elevated risk associated with the use of timber, a combustible material, has been recognised since the 2019 changes to the Scottish Building Standards Technical Handbooks, which provide guidance for complying with the Building (Scotland) Regulations 2004. Specifically, within Section 2 (Fire) of the Technical Handbooks, it is stated that due to the generic nature of the guidance it cannot address fire safety design using “new or innovative methods of construction” for example where “elements of a structure are engineered timber, including cross laminated timber”. That is not to say that designing and constructing safely with mass timber in Scotland is not possible, but to do so a performance-based fire engineering approach is necessary, with reference to BS 7974:2019 Application of fire safety engineering principles to the design of buildings – Code of practice.
A performance-based fire engineering approach is one which relies upon first principles to provide a comprehensive, quantified, and safe design, which meets the intent of the Building (Scotland) Regulations 2004 and, where required, other stakeholder requirements. Often this type of approach demands a significant investment of time and resources from the project fire engineer and other stakeholders at an early stage of design to achieve a robust solution, as quality research and testing can be required to inform design decisions.
To add to the complexity of regulatory compliance when the use of mass timber is proposed:
- There are 32 local authorities across the country, presenting a challenge engaging with the varied stakeholders across different local authorities
- There is little precedence in Scotland for large mass timber buildings, meaning that third party reviews and further consultations with the approving bodies and statutory consultees, e.g., Scottish Fire and Rescue Service, are required to provide assurance of a design
To overcome these challenges, the Scottish Government should seek to develop guidance for accessible, prescriptive solutions for lower risk mass timber buildings, which are accepted across all 32 local authorities. A consolidated framework, with the support of a centralised hub, is needed within the Scottish construction industry to engage and support regulatory approving authorities and stakeholders to technically quantify the safe adoption of more complex mass timber in construction.