Apply the answer
Turn the symptoms into the next useful check.
RoofHub can help separate likely roof, moisture, drainage and maintenance issues before you decide whether pricing is the next step.
Start with the symptom, then test the likely causes
| What you notice | Possible areas to investigate first | Do not assume |
|---|---|---|
| Ceiling stain after wind-driven rain | Nearby penetrations, valleys, wall junctions, flashings, laps and damaged cladding. | That the stain is directly below the entry point. Sources: NZ Metal Roofing Manufacturers; NZ Metal Roofing Manufacturers. |
| Droplets/mould in roof space in cold weather | Indoor moisture, ceiling air leakage, insulation, underlay and ventilation strategy. | That every droplet means a hole in the roof. Sources: Building CodeHub / BRANZ; BRANZ. |
| Rust around cuts, laps, fixings or unwashed areas | Coating condition, contaminants, compatible materials and whether corrosion has perforated the sheet. | That painting can rebuild failed steel. Sources: NZ Metal Roofing Manufacturers; NZ Metal Roofing Manufacturers. |
| Spouting overflows in heavy rain | Blockage, fall/outlets/downpipes, roof catchment and whether the gutter was sized for the design rainfall. | That adding another downpipe always solves the system. Sources: NZ Metal Roofing Manufacturers; Building CodeHub / MBIE. |
| Loose or noisy roofing in wind | Fixings, sheet edges, wind damage and local movement. | That tightening a random screw is a complete wind-load assessment. Sources: Roofing Association of New Zealand. |
| Cracked, shifted or deteriorated tiles | Local tile condition, fixings/battens, underlay and the extent of repeated failures. | That one broken tile means the whole roof must be replaced. Sources: Roofing Association of New Zealand. |
What information makes a roof problem easier to diagnose?
- When it occurs: only heavy rain, wind-driven rain, winter mornings, all the time.
- Exact indoor location and whether it moves or spreads.
- Roof material and approximate age if known.
- Nearby roof features: valley, chimney, skylight, wall junction, solar panel or gutter.
- Photos from the ground and inside the roof space where safe.
- Any recent roofing, solar, aerial, HVAC or cleaning work.
- Whether the issue is isolated or repeated in several areas.
This context helps separate a roofing defect from condensation, plumbing or another source. It also gives a roofer something more useful than “the roof leaks somewhere”. Sources: Building CodeHub / BRANZ.
When should you treat it as urgent?
- Active water entry near electrical fittings.
- Loose roofing or debris after a storm.
- Sagging, visibly unstable or severely corroded roofing.
- A suspected asbestos roof that has been broken, drilled or high-pressure cleaned.
- Overflow from internal gutters or drainage that can enter the building.
- Any situation that would require an untrained person to climb onto an unsafe roof to investigate.
Does a problem mean repair or replacement?
Not by itself. A local failed flashing or isolated sheet can be a repair; repeated failures, widespread corrosion, brittle roofing or a roof system at the end of its practical service life can make replacement more sensible. The condition and extent matter more than the drama of a single symptom. Sources: Roofing Association of New Zealand.
Related questions
Why is my roof leaking only when it is windy?
Wind-driven rain can expose junctions that do not leak in vertical rain, including flashings, penetrations and laps. The entry point can also be upslope or sideways from the visible ceiling stain. Sources: NZ Metal Roofing Manufacturers; NZ Metal Roofing Manufacturers.
Does rust mean I need a new metal roof?
Not automatically. Surface corrosion can sometimes be prepared and protected, while perforation or widespread loss of substrate is a different problem. The extent and location of corrosion matter. Sources: NZ Metal Roofing Manufacturers.
Why does my gutter overflow only in very heavy rain?
Possible causes include blockage, outlet/downpipe constraints, poor fall or a system that is undersized for the catchment and design rainfall. Roof drainage should be checked as a system rather than by guessing from one component. Sources: Building CodeHub / MBIE; NZ Metal Roofing Manufacturers.
Sources and review notes
Prepared by RoofHub editorial. Reviewed . A source check confirms what a page states, not an independent inspection or invoice audit. Published project accounts are attributed to their publishers.
- 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
- primaryNZ Metal Roofing Manufacturers: Code of Practice v26.09: Preventative maintenance - Current MRM guidance on preventative maintenance in vulnerable areas, including severe marine micro-environments and unwashed areas. Used alongside the selected product manufacturer warranty and care requirements. Page checked 2026-10-21. Publication date not stated. · industry-technical
- primaryBuilding CodeHub / BRANZ: Roof space moisture – it’s complicated - Build 202 (2024) (2024-06-01) - BRANZ discussion of roof-space moisture sources and controls. It warns that the moisture source is not always the roof and covers warm roofs, cold roofs and ventilation as part of a wider moisture strategy. Page checked 2026-10-21. Publication date shown above. · industry-technical
- primaryNZ Metal Roofing Manufacturers: Code of Practice v26.09: Roof penetrations - Current NZMRM roof-penetration guidance. Penetration detailing depends on hole size and shape, roof pitch and type, catchment area, position and durability/compatibility requirements. Page checked 2026-10-21. Publication date not stated. · industry-technical
- primaryBRANZ: Roof space ventilation (2018-12-01) - BRANZ bulletin explaining that roof-space ventilation in NZ is primarily about moisture management above ceiling insulation and below roof cladding. Retained as technical background alongside the current MRM Code of Practice. Page checked 2026-10-21. Publication date shown above. · industry-technical
- primaryNZ Metal Roofing Manufacturers: Code of Practice v26.09: Overpainting - Current NZMRM generic preparation and overpainting guidance for metal cladding. It stresses correct preparation, compatible primers/coatings and following the coating supplier instructions. Page checked 2026-10-21. Publication date not stated. · industry-technical
- primaryNZ Metal Roofing Manufacturers: Code of Practice v26.09: Roof drainage terminology - Current NZMRM terminology for external gutters/spouting, internal gutters, secret gutters, valleys and related roof-drainage terms. Page checked 2026-10-21. Publication date not stated. · industry-technical
- primaryBuilding CodeHub / MBIE: Acceptable Solution E1/AS1: Surface Water, Amendment 12 (2023-11-02) - Current Building CodeHub record for E1/AS1 Amendment 12. Provides one compliance pathway for disposal of surface water, including roof drainage; project design must use the applicable current compliance route and local rainfall information. Page checked 2026-10-21. Publication date shown above. · government
- primaryRoofing Association of New Zealand: Maintenance Tips - RANZ homeowner maintenance guidance covering drainage, signs of deterioration and working-at-height safety. Used as practical industry context alongside product-specific manufacturer requirements. Page checked 2026-10-21. Publication date not stated. · industry-technical
- 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
- primaryWorkSafe New Zealand: Roof restoration and maintenance - WorkSafe guidance for roof restoration and maintenance tasks. It applies the working-at-height control hierarchy and identifies brittle roofing, inspections, cleaning, repairs and coating work as roof-access hazards requiring suitable controls. Page checked 2026-10-21. Publication date not stated. · government
- 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
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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