NCC 2025 condensation management changes

NCC 2025 introduces updated condensation management requirements for residential buildings under Volume Two and the Housing Provisions.

The changes are intended to reduce the risk of condensation, mould, timber decay, corrosion and damage to insulation by improving the way moisture is managed within wall and roof systems.

For Canberra and the broader ACT region, which generally falls within Climate Zone 7 – cool temperate, condensation risk is higher due to cold winters and large temperature changes. Builders should ensure condensation management is considered at design stage, not left to site interpretation.

Key items to check include:

• use of appropriate vapour permeable wall membranes, particularly Class 4 membranes where required;
• compliant drained and ventilated cavities behind cladding systems where required;
• roof space ventilation that suits the roof type, pitch and insulation layout;
• exhaust fans from bathrooms, kitchens, laundries and sanitary compartments discharging to outside air correctly;
• insulation installed without blocking ventilation paths;
• wall wraps, sarking, tapes, flashings and penetrations installed as a complete system.

Members should also review manufacturer installation requirements for wall wraps, cladding systems and proprietary ventilation products, particularly where direct-fix cladding, skillion roofs, cathedral ceilings or low-pitched roofs are proposed.

In the ACT, NCC 2025 commenced on 1 May 2026 and becomes mandatory on 1 May 2027. During the transition period, the NCC version being used should be clearly documented and applied consistently.

Members are encouraged to speak with their designer, certifier, energy assessor and product suppliers early to confirm the correct condensation management pathway for each project.

If you’d like support reviewing your processes, please reach out to the MBA ACT team.

📞 (02) 6175 5900
📧 workplace@mba.org.au