Moisture trapped behind exterior cladding is one of the most damaging — and common — problems facing New Zealand homes, particularly those built between the late 1980s and early 2000s. The good news is there are several practical ways to check for warning signs yourself, though a licensed building inspector should always carry out a thorough assessment if you have real concerns.
Why Moisture in Cladding Is Such a Big Deal in NZ
New Zealand's climate — especially in wetter regions like Auckland, the West Coast, and Wellington — creates ideal conditions for moisture to penetrate cladding systems. When water gets in and can't get out, it causes rot, mould, structural damage, and can compromise your home's compliance with the NZ Building Code, particularly Clause E2 (External Moisture). Homes with monolithic cladding (such as fibre cement or EIFS/plaster systems) are especially vulnerable if they lack adequate drainage cavities.
Visual Checks You Can Do Yourself
Start with a thorough walk-around of your home. Look for these warning signs:
- Cracking or bubbling paint on the cladding surface
- Staining or discolouration, particularly dark streaks running downward
- Soft or spongy areas when you gently press on the cladding (never force this)
- Gaps, cracks, or failed sealant around windows, doors, penetrations, and junctions
- Rust stains bleeding through from fixings underneath
- Mould or lichen growth concentrated in certain areas
- Interior signs like peeling wallpaper, damp smells, or staining on internal walls near exterior faces
Pay particular attention to low-slope roof-to-wall junctions, deck connections, window heads and sills, and any area where two different materials meet — these are the most common entry points for water.
The Screwdriver Tap Test
A simple but useful field test is the tap test. Using the handle of a screwdriver, gently tap across the surface of your cladding. Healthy, dry cladding produces a consistent, solid sound. A dull thud or hollow sound in isolated spots can indicate delamination, rot, or a void behind the surface — all potential signs of moisture damage. This works particularly well on fibre cement and timber weatherboard cladding.
Safety note: Never use excessive force. If cladding feels very soft or crumbles, stop and contact a professional — disturbing deteriorated material can expose you to hazards including older paint systems that may contain lead.
Using a Moisture Meter
A pin-type or non-invasive moisture meter is the most practical DIY tool for checking cladding. These are available from hardware stores like Bunnings or Mitre 10 and give you a percentage moisture reading.
How to use one:
- Take baseline readings on a known-dry area of cladding (e.g., a sheltered, north-facing wall).
- Systematically test suspect areas — around windows, at the base of walls, near penetrations.
- Compare readings. Elevated readings (generally above 18–20% for timber) in specific zones suggest moisture accumulation.
Keep in mind that surface moisture from recent rain can skew results. Test after a few dry days for more reliable readings. Non-invasive (capacitance) meters are useful for scanning large areas without damaging the surface, but pin meters give more accurate depth readings.
Checking Sealants and Flashings
Run your finger along all sealant joints around windows, doors, pipes, and roof-to-wall junctions. Sealant that is cracked, shrunk, pulling away, or missing entirely is a direct water entry path. Similarly, check that flashings are correctly lapped, not corroded, and properly bedded. Failed flashings are a leading cause of moisture ingress in NZ homes.
BRANZ provides excellent technical guidance on cladding and weathertightness details that can help you understand what good installation looks like.
What the Results Might Mean
| Finding | Likely Implication | Next Step |
|---|---|---|
| Consistent low moisture readings, no visual defects | Cladding performing well | Monitor annually |
| Isolated elevated readings near junctions | Localised moisture ingress | Reseal and monitor; consider inspector |
| Widespread elevated readings or soft spots | Significant moisture retention | Get a professional inspection urgently |
| Visible rot, structural softness | Active damage underway | Licensed building inspector + builder ASAP |
When to Call a Professional
DIY checks are a useful starting point, but they have real limits. You should engage a licensed building inspector if:
- You find elevated moisture readings in multiple areas
- Your home has monolithic or EIFS cladding (sometimes called "leaky home" cladding types)
- You're buying or selling a property
- You suspect structural damage or widespread rot
- You want a report for insurance or legal purposes
A qualified inspector has access to thermal imaging cameras, calibrated moisture meters, and borescope cameras that can assess moisture without destructive investigation. They can also advise whether any remediation work requires a building consent — always check with your local council, as requirements vary. For guidance on consent requirements and Schedule 1 exemptions, visit MBIE Building Performance.
You can find experienced, local building inspectors and cladding specialists on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
BCITO Qualified
