Technical Booklet G Resistance to the Passage of Sound·Page 45·2.72
Bonded or tied junction between separating wall and external cavity wall
The separating wall must be joined to the inner leaf of an external cavity wall either by bonding (with the separating wall contributing at least 50% of the bond) or by tying the external wall to the separating wall.
The separating wall should be joined to the inner leaf of the external cavity wall by one of the following methods –
(a) Bonded. The separating wall should be bonded to the external wall in such a way that the separating wall contributes at least 50% of the bond at the junction (see Diagram 2.6); or
(b) Tied. The external wall should abut the separating wall and be tied to it (see Diagram 2.21).
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet G - Resistance to the Passage of Sound.pdf