Design codes and procedures
Such buildings are still governed within inner London by Section 20 of the London Building (Amendment) Act 1939. The provisos affect buildings higher than 30m, or 25m if the area of the building exceeds 930m2, or for large trade buildings over 7100m3. The means of escape in case of fire under Section 20 are still controlled by Sections 33 and 34 of the 1939 Act. The requirements are more stringent than those in Code of Practice 3 clause IV or in BS 5588.2
10.5 Mandatory rules for means of escape in case of fire The mandatory rules are prescribed in Part B of Schedule 1 to the Building Regulations (1991) known as Approved Document Bl. These relate to fire compartments sprinklers etc. and should be checked carefully.3 As they do not apply
to the actual design of stairs they have been omitted in this edition.