Reroofing process NZ: what happens before, during and after a roof replacement

1. Before anyone removes the old roof

• Identify the existing roofing and any asbestos or hazardous-material uncertainty.
• Confirm whether the work is repair, like-for-like replacement, an alteration, or a change of roof system.
• Check building-consent and restricted-building-work requirements for the actual project.
• Agree the roof product/profile, coating, flashings, drainage, penetrations and any known repairs.
• Agree access, scaffold/edge protection, site protection, material storage and waste removal.
• Put price, exclusions, allowances, timing, payment and variation rules in writing.

RANZ describes reroofing as a project involving material, system, scope and workmanship decisions. MBIE separately requires all building work to comply with the Building Code even where a consent exemption applies. Sources: Roofing Association of New Zealand; Building Performance.

2. Plan how the building stays dry and safe

Removing roof cladding temporarily reduces the building’s weather protection. The contractor should plan staging around the forecast, the amount of roof opened at once, temporary protection and how unexpected rain will be handled. The exact method depends on the building and roofing system. Sources: Roofing Association of New Zealand.

Roof work is also work at height. WorkSafe guidance expects a work plan covering safe access, roof condition, fall hazards, brittle roofing, weather and appropriate controls. Major roof work normally needs purpose-designed access and edge/fall protection rather than treating a ladder as the work platform. Sources: WorkSafe New Zealand.

3. Remove the old system and inspect what was hidden

Once old cladding, tiles or membrane are lifted, previously hidden substrate, purlins/battens, framing, underlay and fixings can be assessed. This is the point where a quote allowance for unknown repairs may turn into an actual variation. Sources: Roofing Association of New Zealand.

4. Rebuild the roof as a system

The replacement is more than roof sheets. Depending on the system it can involve underlay, battens or purlin interfaces, cladding, fasteners, ridges, hips, valleys, barges, aprons, penetrations and drainage components. Manufacturer instructions and applicable NZ detailing govern the actual installation. Sources: NZ Metal Roofing Manufacturers; NZ Metal Roofing Manufacturers.

If the roofing has been removed from an inaccessible skillion or low roof, it can also be an important opportunity to assess insulation before the cavity is closed again. Sources: Building Performance; Tenancy Services.

5. Finish with records, warranties and maintenance information

• Confirm all agreed roof, flashing, penetration and drainage work is complete.
• Photograph or record any hidden repairs if useful to the owner.
• Collect product and workmanship warranty documents.
• Collect maintenance requirements and product identification.
• For consented/restricted building work, collect the required records and completion documentation.
• Keep the final contract, quote, variations and invoices together.

MBIE consumer-protection guidance requires contractors to provide certain post-build information such as maintenance requirements, guarantees or warranties and applicable insurance documents, regardless of project size. Sources: Building Performance.

How long does the process take?

The on-roof replacement period and the total project lead time are different. Weather, scaffold, material lead times, complex flashings, hidden repairs, inspections and consent can all change the programme. RoofHub keeps its separate reroof-time guide focused on that question. Sources: Roofing Association of New Zealand.

Related questions

Sources and review notes

Prepared by RoofHub editorial. Reviewed 21 October 2026. A source check confirms what a page states, not an independent inspection or invoice audit. Published project accounts are attributed to their publishers.

1. primaryRoofing Association of New Zealand: RANZ Re-Roofing Guide - RANZ describes this as an annually updated NZ consumer guide to reroofing materials, systems, terminology, scope and workmanship. Used for project-planning context rather than contractor ranking. Page checked 2026-10-21. Publication date not stated. · industry-technical
2. primaryBuilding Performance: Check if you need consents (2026-01-15) - MBIE Building Performance guidance. All NZ building work must comply with the Building Code; some low-risk work is exempt from consent, and owners should confirm uncertain cases with their council or an appropriate professional. Page checked 2026-10-21. Publication date shown above. · government
3. primaryWorkSafe New Zealand: Working on roofs - good practice guidelines - WorkSafe roof-work guidance covering safe access, fall hazards, brittle roofing, weather and preferred temporary access such as scaffolding or work platforms. Page checked 2026-10-21. Publication date not stated. · government
4. primaryBuilding Performance: Contracts for your building project (2026-01-15) - Building Performance guidance last updated 15 January 2026. Residential building work costing $30,000 or more including GST requires a written contract; disclosure and checklist requirements also apply at that threshold or when requested. Page checked 2026-10-21. Publication date shown above. · government
5. primaryBuilding Performance: Implied contract terms - MBIE guidance on default residential building contract terms, including payments, variations, consents, subcontractors and disputes where a contract is missing required provisions. Page checked 2026-10-21. Publication date not stated. · government
6. primaryNZ Metal Roofing Manufacturers: Code of Practice v26.09: Underlay - Current MRM guidance describing underlay as temporary moisture absorption/release rather than a substitute drainage plane, and recommending no more than one compliant layer on a profiled-metal reroof except at laps. Page checked 2026-10-21. Publication date not stated. · industry-technical
7. primaryNZ Metal Roofing Manufacturers: Code of Practice v26.09: Flashings - Current MRM flashing guidance. Defines the purpose of flashings and identifies common types including ridge/hip, barge/verge, parapet cappings, apron and valley; penetration flashings are treated separately. Page checked 2026-10-21. Publication date not stated. · industry-technical
8. primaryBuilding Performance: Insulation for existing homes (2025-03-31) - MBIE existing-home insulation guidance. For ceilings without accessible roof spaces, replacing the roofing or ceiling lining can be a useful opportunity to insulate; moisture and clearance details still need correct design and installation. Page checked 2026-10-21. Publication date shown above. · government
9. primaryTenancy Services: Insulation standard (2025-09-25) - Healthy Homes insulation guidance, last updated 25 September 2025. Rental-property obligations have specific rules and exemptions; inaccessible roof cavities may need attention when reroofing makes them accessible. Page checked 2026-10-21. Publication date shown above. · government
10. primaryBuilding Performance: Protection for homeowners - Homeowner consumer-protection guidance covering the $30,000 including GST contract threshold, disclosure/checklist requirements and documents that contractors must supply when work is completed. Page checked 2026-10-21. Publication date not stated. · government
11. primaryBuilding Performance: Restricted building work (2026-01-15) - Explains restricted building work and the requirement for appropriately licensed practitioners where residential work is consented and affects primary structure or weathertightness. Page checked 2026-10-21. Publication date shown above. · government

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.

Keep exploring