Technical Booklet G Resistance to the Passage of Sound·Page 86·3.109
Cavity wall with timber frame inner leaf - cavity closure
Requires cavity stops for external cavity walls with timber frame inner leaves.
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.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet G - Resistance to the Passage of Sound.pdf