NCC Assessment Methods: How to Prove Your Building Complies

The National Construction Code sets minimum technical requirements for new buildings and new work in existing buildings. And like any code worth its salt, it doesn't just tell you what to achieve. It tells you how to prove you've achieved it.

That's where Assessment Methods come in.

The Compliance Framework

You've got two paths to NCC compliance: Deemed-to-Satisfy (DTS) Solutions, which follow the code's prescriptive provisions to the letter, or Performance Solutions, which achieve the same outcomes through alternative means. Most projects use a combination of both.

Either way, you need to demonstrate compliance. Assessment Methods are the tools you use to do that. The NCC lists four, and you can use any combination depending on what you're proving.

Performance Solutions and the Performance-Based Design Brief

Performance Solutions don't work on trust. There's a process, and at its centre is the performance-based design brief (PBDB).

A PBDB is a document developed collaboratively with stakeholders before you start designing. Think of it as a contract: everyone agrees upfront on what you're trying to achieve, how you'll prove it, and what "success" looks like. The purpose is to eliminate surprises. Get alignment early, and approval becomes far more predictable.

The stakeholder list typically includes the building owner (or representative), builder or project manager, relevant design practitioners (architects, engineers, specialists), the appropriate approval authority, and any other relevant agencies. The process usually starts with round-table discussions initiated by the designer.

A typical PBDB covers the proposal summary (building type, function, height, location), a description of the proposed solution, applicable Performance Requirements, agreed analytical assessment processes, acceptance criteria, required supporting evidence, and report format. Stakeholder sign-off creates a clear record of commitments.

The Four-Step Process

Step 1: Prepare the PBDB. Scope the solution, consult stakeholders, document everything, get sign-off.

Step 2: Carry out analysis. Complete the analytical assessment as agreed. This might involve comparative or absolute analysis, calculations, testing, or modelling.

Step 3: Evaluate results. Compare results against agreed acceptance criteria. If outcomes don't meet criteria, revisit your methods or conduct further analysis.

Step 4: Prepare the final report. Demonstrate compliance with the Performance Requirements agreed in the PBDB. This includes an overview of the PBDB, outline of analysis undertaken, evaluation of results against acceptance criteria, and conclusions (including any limitations or conditions of use).

The key takeaway: Performance Solutions can be straightforward if you start with a properly developed PBDB. Getting alignment upfront saves considerable grief later.

The Four Assessment Methods

Evidence of Suitability

This is your documentary evidence, demonstrating that a material, product, or form of construction does what you're claiming.

Acceptable forms include reports from Accredited Testing Laboratories, Certificates of Conformity or Accreditation, certificates from professional engineers or appropriately qualified persons, certificates from JAS-ANZ accredited product certification bodies, and any other documentary evidence that adequately demonstrates suitability (such as Product Technical Statements).

Volume Three has an additional requirement: WaterMark certification. For certain plumbing and drainage products, a WaterMark Licence is mandatory evidence of suitability.

Comparison with the DTS Provisions

This one's for Performance Solutions. The logic is straightforward: demonstrate your alternative approach is at least as good as following the DTS Provisions, and you've met the Performance Requirements.

The catch is that "at least as good" needs like-for-like analysis. Apply the same methodology to both approaches (computer modelling is common here). If your solution delivers equivalent or better health, safety, amenity, or sustainability outcomes, you're compliant.

Verification Methods

Verification Methods are tests or calculations prescribing specific ways to demonstrate compliance. They come with quantifiable benchmarks or predetermined acceptance criteria.

The NCC includes several built-in Verification Methods (D1V1 for wire barriers, H2V1 for weatherproofing, B2V1 for heated water storage temperature, among others). But you're not limited to what's in the NCC. Other methods can be used if the appropriate authority accepts them, including overseas codes and standards like ISO.

Verification Methods generally take one of these forms:

A test. Something like an on-site field test measuring actual thermal performance of an installed window.

An inspection. Typically a visual examination by an appropriately qualified person, such as an engineer confirming timber framing installation.

A calculation. Engineering calculations (hand or computer modelling) verifying a design meets Performance Requirements. The fire separation methodology in C1V1 is a good example.

Other methods. Almost any suitable methodology, provided the appropriate authority agrees it's acceptable.

Expert Judgement

When physical criteria fall outside what's practical to test or model, you turn to Expert Judgement: the opinion of someone with qualifications and experience to determine whether a solution complies.

Who counts as an expert depends on jurisdiction. Different states and territories have different registration requirements. Ultimately, the appropriate authority decides whether a particular person is qualified to provide judgement on a particular issue.

One limitation: the appropriate authority can't provide Expert Judgement for a matter they're also assessing for approval. Independence matters.

A Note on Appropriate Authorities

An appropriate authority is whoever has statutory responsibility for enforcing building and plumbing regulations in your jurisdiction. State and territory regulations define who qualifies, but generally you're looking at building surveyors or plumbing inspectors.

Documentation

Assessment Methods are only as useful as the documentation backing them up. Your documentation needs to clearly show the appropriate authority which Performance Requirements and/or DTS Provisions apply, which Assessment Methods you've used, the PBDB and analysis (for Performance Solutions), confirmation requirements have been met, and any conditions or limitations.

The level of detail required is the appropriate authority's call. Expert Judgement documentation might be a simple email or a full technical report. Verification Method documentation might include software specifications or detailed test records.

Match your documentation to the complexity of what you're proving, and confirm expectations with your appropriate authority early. It saves everyone time.