BASIX at Construction Certificate Stage

BASIX does not stop being relevant once a Development Application or Complying Development Certificate has been lodged. For many NSW residential projects, BASIX becomes especially important again at construction certificate stage because the plans and specifications need to show how the BASIX commitments will actually be delivered.

NSW Planning explains that before building begins, a construction certificate is needed. The BASIX Certificate must be attached to the construction certificate application and all BASIX commitments must be shown on the plans. This means the construction documentation needs to align with the certificate, not just the original planning drawings. NSW Planning Portal

What is the construction certificate stage?

A construction certificate is part of the post consent process for many building projects in NSW. NSW Planning describes a construction certificate as confirming that the construction plans and development specifications comply with the Building Code of Australia and other council requirements. A construction certificate must be obtained before building or construction work starts, unless the work is exempt, complying development or Crown building work. NSW Planning Portal

For BASIX projects, this stage is where the approved sustainability commitments need to be carried through into the construction drawings and specifications. The certifier will need enough information to see that the project can be built in accordance with the BASIX Certificate.

Why BASIX matters after DA approval

A common mistake is assuming that BASIX is finished once development consent is granted. In reality, the BASIX Certificate records sustainability commitments that must continue through later project stages. NSW Planning states that if the application is approved, the project must be built according to the BASIX commitments. NSW Planning Portal

This means the construction certificate drawings cannot ignore the BASIX Certificate. If the certificate includes commitments for glazing, insulation, rainwater tanks, hot water, solar panels, heating, cooling, ventilation, pools or spas, those commitments need to be visible or supported in the construction documentation.

What needs to be shown on construction certificate plans?

At construction certificate stage, the plans and specifications should show the BASIX commitments clearly enough for the certifier to review them. Some commitments may be shown as notes, while others may need to appear in plans, elevations, schedules, sections, specifications or services documentation.

Common BASIX commitments that may need to be shown include:

• Glazing performance, window sizes, U value and SHGC where specified.
• Wall, roof, ceiling and floor insulation values.
• External shading, eaves, awnings, balconies or other shading devices.
• Hot water system type and energy source.
• Heating, cooling and ventilation systems.
• Rainwater tank size, location, roof catchment and connected uses.
• Solar PV system size and location, where committed.
• Water efficient fixtures.
• Pool or spa volume, cover, heating, pump, timer and top-up commitments.

DA plans versus construction certificate plans

DA plans and construction certificate plans are not always identical. After development consent, the design may be refined for construction, coordination, structural documentation, window procurement, services design or builder preferences. These changes can be normal, but they need to be checked against BASIX if they affect water, energy or thermal performance commitments.

For example, if window sizes change, the glazing specification changes, insulation is reduced, a rainwater tank is moved, solar panels are removed or the hot water system changes, the original BASIX Certificate may no longer match the construction certificate set. In that case, the certificate should be reviewed before submission.

Can BASIX be amended before construction certificate?

Yes. BASIX may need to be amended before construction certificate if the project has changed since the original certificate was issued. This is common where the design has been refined after DA approval or where builder selections affect the original assessment assumptions.

The key question is whether the change affects the certificate commitments or the BASIX outcome. Some changes may not require a new certificate, while others may affect thermal comfort modelling, water commitments, energy systems or the overall BASIX score. The safest approach is to check before submitting the construction certificate package.

Glazing and window changes at CC stage

Window changes are one of the most common reasons BASIX needs to be reviewed at construction certificate stage. During detailed documentation, windows may be resized, repositioned, grouped, deleted or changed to suit supplier availability. Frame type, glass type, U value and SHGC may also change when the window schedule is finalised.

Because glazing can affect thermal comfort, cooling load and heating load, the BASIX Certificate and any NatHERS modelling should be checked if the construction certificate window schedule differs from the original assessment drawings.

Insulation and construction changes at CC stage

Insulation and construction systems can also change during construction documentation. Wall systems, roof build-ups, raked ceilings, suspended floors, roof colour and insulation values may be refined after planning approval. These changes can affect BASIX and NatHERS outcomes if they differ from the assumptions used in the certificate.

If the BASIX Certificate commits to specific insulation values or construction assumptions, those commitments should be reflected in the construction certificate plans and specifications. Generic construction notes may not be enough if they conflict with the certificate.

Water and energy system changes at CC stage

Water and energy systems are often refined after DA approval. Hot water systems may change, solar PV may be adjusted, rainwater tank locations may move and pool or spa equipment may be selected in more detail. These items can all be BASIX commitments.

If the construction certificate documentation shows a different system from the BASIX Certificate, the project team should not assume it will be acceptable. The certificate should be reviewed and, where needed, amended so that the plans and commitments match.

What happens if BASIX does not match the CC plans?

If BASIX does not match the construction certificate plans, the certifier may request clarification, amended drawings, updated specifications or an amended BASIX Certificate. This can delay construction certificate issue, especially if the change affects NatHERS modelling or major water and energy commitments.

The issue may also continue into later project stages. NSW Planning states that the construction process is inspected by a certifying authority and a final occupation certificate will only be issued when the certifying authority is satisfied that the project has been built as described on the BASIX Certificate. NSW Planning Portal

How to prepare BASIX for construction certificate

The best approach is to review BASIX before submitting the construction certificate package. This is especially important if the design has changed since DA, if the builder has updated specifications or if the construction documents include more detailed window, insulation, services or stormwater information.

• Compare the BASIX Certificate against the latest construction certificate plans.
• Check that BASIX commitments are shown on plans and specifications.
• Review updated window schedules, glazing values and shading details.
• Check insulation, construction systems, roof colour and floor details.
• Confirm hot water, heating, cooling and ventilation systems.
• Confirm rainwater tanks, solar PV, pool and spa commitments.
• Ask for BASIX review before submitting if the plans have changed.

How Certified Energy can help

Certified Energy prepares and reviews BASIX Certificates for NSW residential projects, including projects moving from DA approval into construction certificate documentation. Our team can compare the BASIX Certificate against the latest plans, identify mismatches and advise whether an amendment may be needed.

This is especially useful for projects where window schedules, insulation, roof forms, hot water systems, rainwater tanks, solar panels, pools or spas have changed since the original BASIX Certificate was issued.

Related resources

• Complete Guide to BASIX Certificates in NSW
• BASIX Certificate Service
• Does My BASIX Certificate Need to Match My Plans?
• Can a BASIX Certificate Be Amended?
• Common BASIX Mistakes That Delay Approval

Frequently asked questions

Is BASIX needed at construction certificate stage?

Yes. At construction certificate stage, the BASIX Certificate must be attached to the application and all BASIX commitments must be shown on the plans. The certifier needs to confirm that the construction documentation aligns with the BASIX Certificate.

What BASIX commitments need to be shown on construction certificate plans?

BASIX commitments that may need to be shown include insulation, glazing performance, rainwater tanks, hot water systems, solar panels, heating, cooling, ventilation, water fixtures, pools, spas and any other commitments listed on the BASIX Certificate.

Can BASIX change between DA and construction certificate?

Yes. If the design changes between DA and construction certificate, the BASIX Certificate may need to be checked or amended. Changes to windows, insulation, hot water, rainwater, solar, layout, pools or spas can affect the BASIX commitments.

What happens if BASIX does not match the construction certificate plans?

If BASIX does not match the construction certificate plans, the certifier may request clarification, amended plans or an amended BASIX Certificate. Inconsistencies can delay construction certificate issue and may create problems later during occupation certificate checks.