Alternative Flooring

When design meets compliance 

NCC 2022 Volume 2

Area of NCC Requirements:

• H4P1 – Wet areas 
• Housing Provisions Part 10.2 

The Challenge

Laundry floors are treated as wet areas because foreseeable wetting (splashes, overflow, cleaning water) can drive moisture into concealed spaces and damage the building fabric. Under the NCC DTS pathway, “water resistant” laundry floors are typically achieved using nominated surface materials, and the deemed list for water-resistant floor surfaces is restrictive. In this project, a timber floor finish was proposed/retained for a ground-floor laundry in Victoria, which falls outside the DTS material pathway and therefore triggered a compliance gap that required a Performance Solution to demonstrate the H4P1 outcome.

What This Really Means

The NCC outcome is not “tiles by default”; it is preventing water from penetrating behind linings or into concealed spaces in a way that causes dampness, deterioration or unhealthy conditions. Where a non-DTS surface is proposed, the compliance task becomes proving that the floor finish and its interfaces perform as a water-resistant system in service (including at perimeters and penetrations), and that the performance can be verified and maintained over time.

The Solution 

A performance-based assessment was prepared to demonstrate that a timber floor in a laundry can achieve H4P1 by treating the floor as a complete “system”, not just a finish. The assessment considered:

• How the timber surface is made water resistant through a defined protective surface system suitable for laundry exposures.
• How junctions, edges and penetrations are detailed so water does not migrate into concealed spaces.
• Whether a secondary waterproofing measure is used as a redundancy layer rather than the primary compliance mechanism.
• Evidence of suitability. 
• Construction verification requirements.
• Ongoing maintainability.

This layered approach provided a redundancy for habitable basement spaces.

The assessment confirmed that, when compared with NCC intent, the system not only equalled but in some respects exceeded DTS expectations for above-ground weatherproofing.

Why This Matters

The report concluded that the performance solution satisfied NCC requirements for rainwater management, weatherproofing, and rising damp. More importantly, it provided builders and owners with confidence that habitable basements could remain dry, safe, and structurally sound over the long term.

When DTS provisions stop short, performance solutions open the door to international best practice and innovative detailing. For projects involving blockwork basements, this isn’t just about code compliance—it’s about safeguarding investments and creating healthy living environments.

Have similar compliance issues on your project? 

Reach out to our team for the solution.