Technical Booklet G Resistance to the Passage of Sound·Page 86·3.110
Cavity wall with timber frame inner leaf - finish and sealing
Specifies two layers of minimum-mass plasterboard as wall finish with all joints sealed with tape or sealant.
The wall finish of the inner leaf of the external wall should be –
(a) two layers of plasterboard;
(b) each sheet of plasterboard of minimum mass per unit area 10 kg/m2; and
(c) all joints should be sealed with tape or caulked with sealant.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet G - Resistance to the Passage of Sound.pdf