Yes, as a homeowner you can absolutely do a preliminary check for leaky building warning signs — and it's a smart habit to develop. However, a DIY visual inspection has real limits. Many of the most serious moisture problems hide behind cladding, inside wall cavities, and under floors where only a trained building inspector with specialist tools can find them. Think of your own check as a first filter, not a final verdict.
What Is the Leaky Building Problem in NZ?
New Zealand has a well-documented history of weathertight failures, particularly in homes built roughly between the mid-1980s and mid-2000s. Monolithic cladding systems (such as fibre cement or EIFS/plaster systems), complex rooflines, and inadequate detailing around penetrations allowed moisture to enter wall cavities and cause severe framing timber rot. The MBIE Building Performance website has background on weathertight issues and the NZ Building Code requirements (particularly Clause E2 – External Moisture) that now govern new construction.
Visual Signs You Can Check Yourself
A careful walk-around of your property — inside and out — can reveal a surprising amount. Here's what to look for:
Outside the House
- Cladding type: Monolithic plaster or EIFS cladding, especially on homes with parapets, low-pitched roofs, or complex angles, carries higher risk.
- Cracking or bubbling: Fine cracks in plaster cladding, particularly around windows, doors, and corners, are a red flag.
- Missing or deteriorated sealant: Check around window and door frames, penetrations (pipes, vents, meter boxes), and where different cladding materials meet.
- Staining or discolouration: Dark streaks or green algae growth on cladding can indicate persistent moisture.
- Rusting fixings: Rust stains running down from screws or flashings suggest water is tracking in.
- Flashing condition: Look at roof-to-wall junctions, parapets, decks, and balconies. Poorly installed or missing flashings are a leading cause of leaks.
- Deck and balcony waterproofing: Cracked or lifting waterproof membranes on decks that sit over living areas are a serious concern.
Inside the House
- Musty or damp smell: A persistent musty odour, especially in cupboards, under stairs, or in rooms with exterior walls, often signals hidden moisture.
- Staining on walls or ceilings: Yellow-brown water stains, bubbling paint, or peeling wallpaper point to moisture ingress.
- Soft or spongy walls: Gently press on wall linings near windows and exterior walls. Softness can mean the framing behind is wet or rotting.
- Mould growth: Mould on walls, window reveals, or in corners — particularly on exterior walls — is a warning sign. Note that some surface mould is condensation-related rather than a structural leak, but both need attention. Tenancy Services has useful guidance on moisture and mould under the Healthy Homes Standards.
- Sticking doors and windows: Timber framing that has swollen or distorted due to moisture can cause doors and windows to bind.
- Subfloor check: If you have a suspended timber floor, get under the house (safely) and look for wet or discoloured piles, bearers, and joists, or signs of pooling water.
A Simple DIY Inspection Checklist
| Area | What to Check | Warning Sign |
|---|---|---|
| Exterior cladding | Cracks, bubbling, staining | Any cracking at joints or corners |
| Window/door frames | Sealant condition | Gaps, shrinkage, missing sealant |
| Roof flashings | Condition and continuity | Rust, gaps, lifting edges |
| Interior walls | Paint, lining condition | Staining, softness, mould |
| Smell | Musty odour | Persistent damp smell |
| Subfloor | Timber condition | Wet, dark, or soft timber |
The Limits of a DIY Check
Your eyes and nose can only go so far. A qualified building inspector uses tools such as moisture meters, thermal imaging cameras, and sometimes borescopes to detect moisture inside wall cavities without destructive opening. BRANZ — New Zealand's building research authority — has published extensive research on weathertight failures and the difficulty of detecting them without specialist equipment. A professional can also assess risk factors systematically against the NZ Building Code and relevant standards.
If you are buying a property, a pre-purchase building inspection by a Licensed Building Practitioner or similarly qualified inspector is strongly recommended — especially for homes of the era and cladding types described above.
When to Call a Professional
Call a qualified building inspector if:
- You find any of the warning signs listed above during your DIY check.
- The home has monolithic plaster or EIFS cladding, parapets, or complex rooflines.
- You are buying or selling the property.
- You notice a musty smell but can't find an obvious source.
- You want a written report for insurance, legal, or mortgage purposes.
- You are planning renovation work and need to know the true condition of the structure before opening walls.
A Licensed Building Practitioner (LBP) or a building inspector with recognised qualifications can provide a thorough assessment. You can find experienced local building inspectors on tradedirectory.co.nz.
Safety note: When inspecting subfloor spaces, always ensure adequate ventilation, watch for unstable ground, and never enter a confined space alone.
Licensed Building Practitioner (LBP)
BCITO Qualified
