Building Standards (Scotland) Technical Handbook Update
21 Aug 2019
On the 12 July revised Technical Handbooks were published in Scotland. The revisions follow the Scottish consultation on the Building and Fire Safety in 2018 and the revised guidance comes into force on the 1st of October.
The revised handbook is available here.
The changes made are summarised in a summary published here.
The Technical Handbooks have a similar status in Scotland to the Approved Documents in England in that they provide one method of satisfying the building regulations. Other approaches are possible providing it can be demonstrated that they meet the regulations.
Key changes to the fire parts of the Handbook include clarifying the fact that innovative and new methods of construction are not covered by the Handbook. In particular it is noted that engineered timber (including cross laminated timber) is not covered and that a compliance approach for this material would require demonstrating that the structure would maintain stability during a fire without intervention from the fire services.
Where encapsulation cannot be assumed to be effective for the duration of the fire then the additional contribution of the exposed combustible structure to the fire load density should be included in the assessment. The potential for delamination of CLT and/or the failure of fixings at elevated temperatures also requires consideration.
Other changes include the use of the European Classification classes for reaction to fire as the primary method of classification and the introduction of requirements for non-combustible (A1 or A2) material in external walls for any building with a storey more than 11m above ground. The external walls of all hospital’s residential care homes, entertainment and Assembly buildings are required to follow the same requirements.
For domestic buildings this limitation does not apply to insulation when it is between two leaves of masonry or concrete at least 75mm thick. This means there is no limitation on the use of concrete sandwich panels for domestic buildings. The handbook also still permits the use of BS 8414 fire test to demonstrate compliance as an alternative to A1 or A2 materials. Attachments to external walls including balconies and solar shades are also required to be of European Classification A1 or A2 on buildings above 11m tall.
In addition to the additional restrictions on the use of materials the changes introduce a requirement for at least two escape stairs for domestic buildings with a storey height above 18m. There are also requirements for the introduction of an evacuation alert system.
The requirement for separating walls and floors in buildings with a storey above 18m to be of non-combustible materials remains as does the requirement for structure supporting such walls to be non-combustible.
Overall the revised Handbook is a more pragmatic response to the concerns over combustible cladding than the response incorporated into the Building Regulations in England. Whilst the requirements for external walls may be less onerous the restriction on combustible structure in the handbook are more onerous and better reflect the risks associated with modern methods of construction and tall timber structures.
Written by - Tony Jones, principal structural engineer at The Concrete Centre