Does Changing a Window Specification Require a Consent Amendment?
Changing a specification can be straightforward where equivalent-performing alternatives are proposed. In many cases, this may be treated as a minor variation, subject to council review and recording. However, the Building Consent Authority ultimately determines the appropriate pathway based on the supporting performance evidence and the effect of the change on Building Code compliance
The Building (Minor Variations) Amendment Regulations 2024 clarify that substituting a comparable product can be treated as a minor variation, meaning councils are not required to issue an amended building consent, provided performance equivalence & compliance with the building code is maintained. In these cases, councils record the variation on the consent file without requiring a full redraw of plans, making specification changes less disruptive and easier to manage.
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Product Substitution vs Design Change
Councils assess changes based on whether the approved design intent and Building Code compliance pathway are altered,
not simply whether a different product is named.
A window and door change is generally treated as a product substitution when:
- The windows or doors continue to meet the same or better Building Code performance
- Opening sizes and locations remain unchanged
- Structural support and load paths are unaffected
- The same weathertightness strategy and flashing approach are retained
- The compliance pathway relied on in the consent remains unchanged
In these circumstances, the design remains the same. The building is being constructed in the same way, using a different brand but comparable product to achieve the same outcome.
What is more likely to be treated as a design change requiring a formal amendment, where it:
- Alters structure or load paths
- Changes the weathertightness strategy or flashing methodology
- Introduces a new compliance pathway, such as moving from an Acceptable Solution to an Alternative Solution
- Changes how a specified system is relied on for compliance
The key distinction is simple:
If the change alters how Building Code compliance is achieved, it is a design change.
If it only changes which compliant product is used within the same approved design, it is a product substitution.
Councils make the final determination, but MBIE guidance recognises product substitution as a low-risk change when the compliance pathway and design intent are unchanged and the change is supported by clear documentation.
If you are still unsure you can use Simpli's minor variation tool here, the following guides below, or discuss with your local BCA.
MBIE Product Substitution Guidance
Frequently Asked Questions (FAQ):
Q: Do I need to notify the council for a product substitution?
A: Yes. MBIE’s Product Substitution Guidance states that if you intend to substitute a building product originally specified in your building consent, you must notify the Building Consent Authority and show how the new product will continue to comply with the Building Code.
Q: Do I need a consent amendment to change window and door products?
A: Not always. If the change meets the product substitution or minor variation criteria, councils can approve it without issuing an amended building consent. However, councils must be notified and will confirm the correct pathway.
Q: Do drawings need to be redone for a minor variation?
A: Usually no. For minor variations, councils generally accept updated window and door schedules, updated specifications, and references to standard manufacturer details. Full redraws are typically only required where sizes, structure, or weathertightness details materially change.
What happens if only the window brand changes and the flashing details stay the same?
A: In this situation, councils generally treat the change as a product substitution only.
Where:
- Opening sizes remain unchanged
- The same flashing details are used
- Installation aligns with E2/AS1 principles
The change can usually be addressed through updated schedules and references, rather than new drawings. Councils focus on confirming that the original weathertightness design intent has not changed. If you are unsure, check with your local BCA authority for guidance.
When would flashing changes trigger a consent amendment?
A: A formal amendment is more likely to be required if the change:
- Alters the weathertightness strategy or weathering plane
- Introduces a different flashing methodology
- Requires non-standard details or an alternative solution
If the flashing approach changes how moisture is managed, councils will typically require further assessment and may request updated drawings or an amendment.
How does UNO support the process?
A: UNO provides adaptable and efficient end-to-end window & door solutions, including:
- Compliance documentation
- H1 schedules and performance reports
- Standard flashing and installation detail references
- Clear specification support
How do I start a window specification change and who do I contact?
A: The first step is to contact UNO to gather the information needed to support a potential specification change before engaging with council.
UNO can:
- Review the existing window and door specification
- Provide product information, performance data, and standard details
- Masterspec specification reviews
Please note UNO does not determine whether a change is a product substitution or a minor variation. That decision sits with the Building Consent Authority (council).
Once the information is prepared, the proposed change should be submitted to council by the consent holder or their agent, who will confirm whether it can be approved as a minor variation or requires a formal amendment.
This information is provided for general guidance only. UNO accepts no responsibility for reliance on or interpretation of the information provided above and recommends all matters be confirmed with the relevant Building Consent Authority or approved authority for clarity before proceeding.
