Technical Booklet G Resistance to the Passage of Sound·Page 53·2.105
Masonry inner leaf bonding and lining requirements
Where the inner leaf of an external cavity wall is masonry, it must be bonded or tied to the masonry core and lined with independent panels in the same manner as separating walls.
Where the inner leaf of an external cavity wall is masonry –
(a) the inner leaf of the external wall should be bonded or tied to the masonry core; and
(b) the inner leaf of the external wall should be lined with independent panels in the same manner as the separating walls (see Diagram 2.31).
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet G - Resistance to the Passage of Sound.pdf