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Which membrane roof systems are used in New Zealand?
| Family | Typical form | What must be checked |
|---|---|---|
| TPO / other thermoplastic single-ply | Sheet membrane with welded seams. | Named system, membrane thickness, attachment, compatible substrate, details and approved accessories. Sources: ARDEX New Zealand; Nuralite. |
| Butyl / EPDM | Flexible synthetic-rubber sheet systems. | System appraisal or technical literature, substrate, adhesive/joints, falls and installer requirements. Sources: BRANZ; Building CodeHub / BRANZ. |
| Torch-on modified bitumen | Bituminous membrane, commonly multi-layered. | Layer build-up, substrate, fire-safe installation process, outlets and detailing. Sources: BRANZ; Nuralite. |
| Liquid-applied | Applied coating built to a specified membrane thickness. | Substrate preparation, application thickness, curing/site conditions and compatible details. Sources: BRANZ; Nuralite. |
How much fall does a membrane roof need?
BRANZ explains that roofs designed to E2/AS1 have a minimum fall of 2 degrees and recommends 3 degrees in its general membrane article to preserve drainage as buildings and substrates move over time. That is general guidance, not permission to substitute one system for another. Sources: BRANZ.
Product-specific evidence can use different ways of expressing fall. For example, the Rubco Butyl BRANZ appraisal lists a minimum roof fall of 1:30 within its stated scope and also specifies substrate and wind limitations. Always check the current document for the exact system being proposed. Sources: Building CodeHub / BRANZ.
Falls, outlets, overflows, internal gutters and junctions work as one drainage design. A low-slope roof cannot be assessed from membrane brand alone. Sources: BRANZ.
Why does the substrate matter so much?
Membranes rely on a continuous substrate and detailed junctions. The accepted substrate varies by system and may include treated plywood, proprietary roof sarking or concrete within stated conditions. Movement joints, penetrations and transitions need system-compatible detailing. Sources: Building CodeHub / BRANZ; ARDEX New Zealand.
- Identify the exact substrate and treatment/specification.
- Confirm the membrane system is approved or supported for that substrate.
- Check falls before the membrane is installed, not only after.
- Coordinate outlets, overflows, parapets, penetrations and internal gutters.
- Confirm protection where later trades or maintenance traffic could damage the membrane.
- Use the system supplier's current details and required installer pathway.
How should membrane roofing be priced?
Membrane pricing is unusually sensitive to substrate preparation, perimeter and upstand detailing, outlets, penetrations, insulation or warm-roof build-up, protection and the selected proprietary system. An area-only rate can hide too much of the job. Sources: Nuralite; ARDEX New Zealand.
What should you look for in a membrane roofing quote?
- Exact proprietary membrane system and membrane thickness/build-up.
- Substrate and any preparation, replacement or levelling allowance.
- Designed falls and drainage outlets/overflows.
- Perimeters, upstands, parapets, penetrations and internal gutter details.
- Insulation or warm-roof components if applicable.
- Required approved or trained installer status.
- Warranty documents, maintenance conditions and excluded traffic/protection work.
- Scaffold/access and any separately priced building work.
Related questions
Is TPO the same as every membrane roof?
No. TPO is one membrane family. Butyl/EPDM, modified-bitumen torch-on, PVC/KEE and liquid-applied systems have different products and build-ups. Sources: BRANZ; Nuralite.
Why does RoofHub not show a membrane estimate yet?
The current RoofHub estimator has no approved membrane rate pathway. Rather than map membrane work onto a metal-roof model or an unsupported market average, RoofHub leaves the price unconfigured until the calculation method and evidence are reviewed.
Sources and review notes
Prepared by RoofHub editorial team. Reviewed . A source check confirms what a page states, not an independent inspection or invoice audit. Published project accounts are attributed to their publishers.
- primaryBRANZ: Membranes do matter - BRANZ technical overview reviewed 20 October 2026. Covers torch-on bitumen, butyl/EPDM, liquid-applied, TPO and PVC membrane families and explains low-slope design and consent considerations. Its general fall guidance is not substituted for the requirements of a selected proprietary system. Page checked 2026-10-20. Publication date not stated. · industry-technical
- primaryBuilding CodeHub / BRANZ: Rubco Butyl Membrane Systems - Appraisal 1006 (2023) (2023-08-21) - Product-specific BRANZ appraisal surfaced through Building CodeHub. Shows how substrate, roof/deck fall, wind scope and approved-applicator conditions belong to a named membrane system rather than a generic membrane rule. Page checked 2026-10-20. Publication date shown above. · industry-technical
- primaryNuralite: Waterproof Membrane Options - Manufacturer overview reviewed 20 October 2026. Compares single-ply TPO/EPDM/PVC-KEE, multi-layer bituminous and liquid-applied membrane families. Used for system-selection context, not independent performance ranking. Page checked 2026-10-20. Publication date not stated. · manufacturer
- primaryARDEX New Zealand: TPO Roofing Systems - Manufacturer system page reviewed 20 October 2026. Confirms TPO is supplied as a complete roofing system with membranes and accessories. Product-specific technical literature remains the authority for installation and detailing. Page checked 2026-10-20. Publication date not stated. · manufacturer
Original calculations are labelled as examples. Historical prices stay dated, missing fields stay unknown, and conflicting specifications are flagged. Sources are not endorsements or paid rankings. Read our methodology or report a correction.
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