Technical Booklet G Resistance to the Passage of Sound·Page 53·2.104
Cavity closure requirements for external cavity walls
External cavity walls must be closed with a cavity stop unless the cavity is fully filled with mineral wool or expanded polystyrene beads.
Where the external wall is a cavity wall –
(a) the outer leaf of the wall may be of any construction; and
(b) the cavity should be closed with a cavity stop (see Diagram 2.31) unless the cavity is fully filled with mineral wool or expanded polystyrene beads (seek manufacturer's advice for other suitable materials).
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