SIPs, are an advanced, modern method of Timber Frame construction,
offering far superior insulation, structural strength and air-tightness
than traditional systems
All forms of construction need to comply with the fire performance requirements laid down by national Building Regulations and there is no difficulty in SIP-based structures meeting the required levels, given correct design, standards of manufacture and workmanship.
The fire resistance of SIP external walls is provided by the wall linings. These wall linings are typically plasterboard, although other types of fire resistant board could also be used.
Typically, one layer of 15mm Type F (fire/high temperature) plasterboard fixed to timber battens forming a nominal service void will provide 30minutes fire resistance to a SIP wall regardless of the type of SIP or the core insulation material. 60minutes fire resistance to any type of SIP can be achieved with two layers of 15mm Type F (fire/high temperature) plasterboard fixed to timber battens forming a nominal service void.
Note: For infill walling applications above 18m the external wall must meet the performance criteria given in BRE report BR315/BS8414
Generally, roof structures do not require specified periods of fire resistance unless the roof structure forms an escape route, or the roof void is a habitable space. If the roof is a habitable space, the floor to the room-in-roof would need to provide either 30 or 60minutes fire resistance. Normally these floors are either timber joists or large room-in-roof trusses and fire resistance would be provided in a similar way to the protection of timber joisted floors with the use of plasterboard. If the roof structure forms a means of escape, fire resistance requirements would need to be considered on a project specific basis.
BRE Information Paper ref: IP21/10 summarises the results of a number of fire resistance tests conducted on small and large scale samples of SIP buildings. These tests were funded by DCLG, the Department for Communities and Local Government and conducted at an independent laboratory to determine the performance of SIP systems exposed to realistic fire scenario.
A full transcript of the test results can be seen in IP21/10 which can be downloaded here. Additional information can be found within the Structural Timber Association SIPS Technical Bulletin 2 and SIPS Pocket Guide.