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Do You Need a Waterproofing Performance Solution in NSW?

Written by Kevin Ly

Usually someone else says it first: a certifier looking at a balcony door that sits level with the tiles, a builder describing a walk-in shower, or an inspection that finds the work doesn't match the standard detail.

A level balcony door, or a hobless shower in a house, does not automatically need a performance solution. Before paying for a report, ask the builder or certifier to identify the detail in question, the provision it departs from, and whether a standard detail or rectification is an option.

What a performance solution is

The National Construction Code (NCC) has two routes to compliance, and they can be combined. The Deemed-to-Satisfy route follows the standard details set out in the NCC and the Australian Standards it calls up. A performance solution is the other route: a documented case that a design meets the NCC's Performance Requirements, or is at least equivalent to the standard details, without following them.

It is design work, and the certifier decides whether to accept it. A waterproofer's certificate is the installer's statement about their own work. A performance solution has to show why a design outside the standard details still meets the code.

First, work out which situation you're in

  1. The design leaves the standard details on purpose. The decision is made before anything is built. In NSW, before issuing a construction certificate for that work, the certifier must have the performance solution report, and the plans have to show the solution's physical elements where possible.
  2. The work is built, doesn't match the standard details, and it turns up at the certifier's final inspection. NSW guidance for certifiers covers this case: a certifier who is qualified to approve a performance solution has to check it is still consistent with the work approved in the construction certificate. The same guidance warns that a construction certificate can only be given for future work. Fixing the work is the other option. Price both.
  3. The work needed approval and never got it. A construction certificate can't approve work that has already been done. NSW guidance says a building information certificate from council is usually the only way to 'regularise' unauthorised work. It isn't an approval: it means council won't take enforcement action against the work. Our page on building information certificates covers it.

Does a level balcony door need a performance solution?

Not automatically. Where it applies, the waterproofing standard AS 4654.2 already has a route for a level door. Where the inside and outside floor levels don't allow the membrane to turn up at the door, the membrane is fixed under the sill and ends in the stormwater system. Building Commission NSW quotes that clause in its building defects guidance. Where the membrane does turn up, the standard requires it to finish high enough to stop water, including wind-driven water, flowing over the top.

AS 4654.2 applies on apartment buildings to balconies and podiums unless they are directly above the ground or have timber decking or other perforated flooring, and on houses to balconies and terraces above rooms.

Before commissioning a performance solution, ask whether the concern is the level itself, the drainage at the door, or evidence that the membrane runs under the sill. A performance solution comes in when the standard routes don't suit the design or the site.

Does a hobless shower need a performance solution?

A hobless shower in a house does not automatically need a performance solution; the answer depends on the design. For houses, the ABCB Housing Provisions list a level threshold alongside hobs and step-downs as standard shower options. An enclosed shower with a level threshold needs a waterstop at the edge of the shower area that finishes at least 5 mm above the floor where a screen is fitted. An unenclosed shower needs a waterstop at least 1500 mm from the shower rose, set flush with the floor.

The practical problem can be depth: getting the falls to the waste without a hob can mean recessing a slab or packing up a timber floor. For a house, a performance solution comes in when the design leaves both the Housing Provisions and AS 3740, the wet-area standard. In an apartment, the standard route is AS 3740, so it comes in when the design leaves that.

Two more points for NSW. The NCC's livable housing provisions don't apply to houses in NSW, although some answers online mix them in. And a renovation done as exempt development, with no approval, has to meet the deemed-to-satisfy provisions under the NSW Codes SEPP, so a design that relies on a performance solution needs an approval, such as a complying development certificate, or development consent and a construction certificate.

Can a performance solution help with finished work?

Sometimes, for approved work, as the second situation above describes. Where it can, it has to rest on what can be shown about the work: which membrane, how thick, where it stops, the falls, and whether it holds water in a flood test. Once the tiles are down, most of that is hidden. A visual inspection records what's visible; it can't show the concealed membrane.

The evidence can come from records made during construction, such as photographs of the membrane, the product used and the installer's certificate. Where those are missing, it can come from testing or limited opening-up, agreed with the certifier in advance. Our article on proposing a test to your certifier covers how to set that up.

Who prepares the report, and what should it contain?

Under the NCC, a performance solution goes through four steps: a performance-based design brief prepared with the relevant stakeholders, analysis, an evaluation against the brief's acceptance criteria, and a final report. The report has to include:

If a builder tells you the work "is a performance solution", ask to see that report and the certifier's acceptance of it. Without a documented performance solution, the work has to meet the standard details. The conditions are what gets built on site, so it helps to have the work recorded against them as it goes.

Who can prepare one, as at September 2026:

What we do, and what it costs

Certified Waterproofing handles both parts of a performance solution: the design and the evidence. We prepare the waterproofing design and the performance solution report, and for apartment buildings they are prepared and declared by our registered design practitioner. We also record the evidence a performance solution depends on: inspections, photographs, measurements of falls and heights, and flood tests run by your plumber. During construction, we record the work against the report's conditions for the certifier. Your certifier decides whether to accept the performance solution.

Guide fee for a performance solution covering two bathrooms: about $3,000 + GST. Your quote will set out the scope and what's included.

Email the written request, your suburb, whether it's a house or an apartment, and whether the work is proposed or finished. Include any drawings and construction photos. We'll confirm the next step, who needs to assess it and any fee before paid work begins.

Send your waterproofing query

What's changing

The Building (Approvals and Practitioners) Act 2026 will replace the Design and Building Practitioners Act and the current certifier laws. As at September 2026, the dates are still to be proclaimed, possibly in stages. NSW adopts NCC 2025 on 1 May 2027, and the edition that applies to a project depends on when its construction certificate is applied for. Under NCC 2025, a new concrete balcony, roof or podium on an apartment building, unless it is directly above the ground, needs a structural slab that falls at least 1:80 and, where applicable, a step down of at least 70 mm from the inside floor slab to the outside slab, among other changes. We will update this page when these change.

This page is general information for NSW as at September 2026, not advice about a particular building.

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