Technical Booklet E Fire Safety·Page 104·4.16
Two-storey Purpose Group 4 or 6 buildings with ancillary upper storey
A two-storey building of Purpose Group 4 or 6 may be treated as a single storey for compartmentation if the upper storey is ancillary and its floor area does not exceed one-fifth of the ground storey or 500 m2 (whichever is less), and the upper storey is a separate compartment.
In the case of a two storey building of Purpose Group 4 or 6, where the use of the upper storey is ancillary to the main use of the ground storey, the ground storey may be treated as a single storey building for compartmentation purposes provided that –
(a) the floor area of the upper storey is not more than –
(i) one fifth of the floor area of the ground storey; or
(ii) 500 m2,
whichever is the lesser; and
(b) the upper storey is a separate compartment.
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