Technical Booklet E Fire Safety·Page 98·Table 4.2 Note (1)
Single storey buildings and basement application
Single storey buildings or separated parts must use the fire resistance period for buildings not more than 5 metres high, with basement storeys subject to periods appropriate to their depth.
A single storey building or a single storey separated part of a building should be subject to the period given under the heading 'Not more than 5' and where it has a basement storey or storeys they should be subject to the period appropriate to their depth.
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