Condensation and waterproofing are two areas NCC 2025 changes, but not equally. The condensation update reaches houses, while the larger waterproofing rewrite is aimed at apartments and commercial buildings. Here's how to work out which change touches your project once NSW adopts the code on 1 May 2027.
Why condensation matters
Showers, cooking and drying clothes all put moisture into the air. When that warm, damp air reaches a cold surface inside a wall or roof, it turns back into water. Over time, hidden moisture can lead to mould, rotting timber, corroded fixings and poor indoor air.
Well-insulated, tightly sealed homes hold on to more moisture, so controlling where it goes matters more than it used to. NCC 2022 introduced specific condensation rules for houses in Part 10.8 of the ABCB Housing Provisions. They cover wall membranes, exhaust fans that discharge outside, and roof space ventilation in cooler climates.
What NCC 2025 changes for houses
The ABCB describes the NCC 2025 condensation provisions as improved, both in Housing Provisions Part 10.8 and in Part F8 of Volume One. One confirmed change is a reduced ventilation requirement for small roofs.
Industry summaries describe the roof ventilation rules being split depending on whether the insulation follows the roof line (as with raked or cathedral ceilings) or sits at ceiling level below a roof space. They also describe more detail on vent placement and how vent area is calculated, with the changes mainly affecting cooler climate zones. Because the exact figures matter, ask your designer to work from the final Housing Provisions text rather than a summary.
Things to check on a house design:
- the climate zone your site sits in
- the roof type, pitch and where the insulation will go
- where high and low level vents are placed
- how wall wraps and roof membranes are specified
- that exhaust fans in bathrooms, laundries and kitchens are ducted to outside air.
Waterproofing: mostly an apartment and commercial change
The major waterproofing work in NCC 2025 is in Volume One, which covers Class 2 to 9 buildings. Part F3 (roof and wall cladding) has been folded into a rewritten Part F1, which deals with surface water, external waterproofing and drainage. New clauses address falls and drainage on concrete roofs and balconies, how membranes are installed, and surface finishes.
NSW has announced a variation for existing apartment buildings. Owners carrying out remedial waterproofing can choose either the current NCC 2022 provisions or the new NCC 2025 provisions. Master Builders NSW suggests confirming the chosen edition in writing with the certifier and designer, and recording it on the drawings and in the contract before work starts.
For houses, wet area waterproofing sits in the Housing Provisions. The official material we reviewed does not point to a comparable rewrite for houses, but your designer should still check the final text. Either way, wet area waterproofing must pass an inspection before anything goes over it, as explained in our Critical stage inspections: what we check and when.
We certify Class 1 and Class 10 work only. Apartment and commercial projects must be certified by someone holding the matching registration.
Practical steps before 1 May 2027
- Confirm when your application will be lodged, since that generally decides which edition applies.
- If it falls from 1 May 2027 onward, have roof and wall details reviewed against NCC 2025.
- Update specification notes that quote old clause numbers.
- Ask for a plan assessment to catch details that need updating, or request a quote for certification.
Local help across NSW
CertifiBuild certifies Class 1 and Class 10 work in 39 council areas. Local rules on these council pages are a good place to start: Randwick City Council, Ku-ring-gai Council, North Sydney Council, Hunter’s Hill Council, City of Canada Bay, Central Coast Council.
Suburb pages with local planning notes: Cremorne Point, Huntleys Cove, Killara, North Sydney, Randwick, Rhodes, St Ives, Turramurra, Warnervale, Warrimoo. You can also browse every service area.
Sources
- Public record of Board meeting, November 2025, ABCB
- Enhanced waterproofing standards, ABCB
- Waterproofing changes in the NCC, Master Builders Association of NSW