AS 2589:2017 Gypsum linings—Application and finishing
2.6.2 Moisture content for Australia
The maximum moisture content for seasoned timber framing at the time of installing gypsum linings shall be less than 15%, in accordance with Appendix E of AS 1684.2. The moisture content of timber framing shall be measured in accordance with Appendix A.
NOTE: Moisture content within the timber frame may be affected by factors, such as environmental conditions refer to AS 1684.2 and AS 1684.3).
2.6.3 Moisture content for New Zealand
Consideration shall be made of the effects of moisture content on the stability of timber substrate at the time of lining. The maximum moisture content for timber framing at the time of installing gypsum linings shall be 18%. The moisture content of timber framing shall be measured in accordance with Appendix A.
NOTES: 1 The permissible moisture content is specified on the basis that 90% of pieces should be below the specified limit with the remainder within a further ±2% moisture content.
2 The requirement of the Clause reflects the requirements for an intermittently heated building such as from open fires or electrical heaters in residential dwellings. NZS 3602 provides recommendations and requirements for situations such as where air-conditioned or centrally heated installations are planned, where a lower timber framing moisture content range at the time of installation of linings should be contemplated (8% to 14%). The objective should always be to install linings to timber framing with a moisture content as close as possible to the final equilibrium level of the completed and occupied building.
2.7.2 Fixing surfaces
The requirements for fixing surfaces shall be as follows:
(a) The substrate members that support a joint (parallel to the member such as required for butt joints) shall have a minimum fixing face width of 32 mm for screw fixing. All other substrate members shall be not less than 30 mm (see Figure 2.6.1). NOTE: This is to facilitate the fixing of board linings.
(b) The maximum deviation in the plane of the fixing face between the edge and the area on the face where the fastener penetrates shall be no more than 0.75 mm (see Figure 2.7.2).
NOTE: This is to prevent bending of the gypsum linings at the edge of the bearing face and unnecessary force imposed on fastener heads.