SCOTTISH EXECUTIVE

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Building Regulations: Technical Standards

D4 Concealed spaces (cavities)

D4.1* Any cavity or roof space must be provided with suitable cavity barriers to restrict the spread of smoke and flame -

a. around the edges of the cavity and between the cavity and any other cavity, and between a roof space and any other roof space;

Table to D4.1: Maximum dimensions of cavities or roof spaces

Notes:

1. Excluding the surface of any cable, conduit, pipe or pipe insulation.
2. The surface classification of materials is given in Table 2 to (E6.1).
3. A roof space must be separated from any other roof space by a cavity barrier between the roof and the ceiling.

b. where a wall, floor or other part of the building which is required to be fire resisting, other than a wall which is required to be fire resisting only because it is loadbearing, abuts a structure containing a cavity. The barrier must be installed so as to extend the line of the fire resisting structure;

c. where the cavity is above a ceiling in a building of purpose group 2, and continues over a wall between bedrooms or between a bedroom and any other part of the building. The barrier must be installed in the same plane as the wall;

d. where the cavity is above a ceiling in a building of purpose sub-group 1A, other than a dwelling, and a building of purpose groups 2-7, and continues over a wall between the accommodation and an unprotected zone, or above a fire door across an unprotected zone. The barrier must be installed in the same plane as the wall and the fire door;

e. where required in Table to D4.1 in addition to any requirement under a., b., c. or d.;

f. within the ventilated void between a rainscreen panel and an external wall at every floor level, and on the line of a compartment wall or separating wall abutting the external wall of a building with a storey at a height of more than 11m;

except -

a cavity barrier is not required by a.-f. above for a cavity which is -

i. between two leaves of masonry or concrete at least 75mm thick, and which has a cavity barrier around all openings in the wall and at the top of the wall, and with no combustible material situated or exposed within the cavity other than -

A. thermal insulating material,

B. a timber lintel, window or door frame or the ends of timber joists,

C. a pipe, conduit or cable,

D. a damp proof course, flashing, closer or wall tie,

E. a meter cupboard in an external wall of a dwelling, provided that -

(a) there are not more than 3 such cupboards to a dwelling, and

(b) the opening in the outer leaf of the wall is not more than 800mm by 500mm for each cupboard; and the inner leaf is not penetrated except by a sleeve of not more than 80mm by 80mm which is fire-stopped; or

ii. at a junction between two walls as described in sub-paragraph i. above; or

iii. between a floor or a roof and a fire resisting ceiling; or

iv. not more than 200mm deep between a structural floor, and a raised floor consisting of removable panels having at least 30 minutes fire resistance for integrity from the underside; or

v. below an imperforate floor next to the ground and the cavity is either inaccessible or is not more than 1m high; or

vi. formed by overcladding, both surfaces of which are at least of class O, attached to a masonry or concrete external wall or a concrete roof and the cavity contains no combustible material; or

vii. in a single-storey framed structure supporting an uninsulated double skin fabric envelope complying with E6.1.

Note: The surface classification of materials is given in Table 2 to (E6.1).

D4.2 In a building with a storey 18m or more above the ground insulation material situated or exposed within cavities in the external wall construction should be non-combustible except -

for a cavity which is specified as in exception i. to D4.1.

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