Yes, as a homeowner you can absolutely do a visual check of your garage for warning signs of structural problems — and it's a smart habit to develop. However, correctly diagnosing the cause and severity of what you find, and deciding what remedial work is needed, is a job for a qualified building inspector or Licensed Building Practitioner (LBP). Think of your role as the first line of observation, not the final word.
Why Garages Are Worth Inspecting
Garages are often built to a lower specification than the main house, and in older NZ homes they may predate modern building standards. They're exposed to weather, vehicle fumes, moisture, and heavy use — all of which can accelerate wear on structural elements. Under the NZ Building Code, garages attached to a house must meet specific requirements around fire separation, drainage, and structural integrity, so problems here can affect your whole home.
What You Can Realistically Check Yourself
A careful walk-around with fresh eyes can reveal a lot. Here's what to look for:
Foundation and Slab
- Cracks in the concrete slab — hairline cracks are common, but wide cracks (wider than about 3 mm), stepped cracks, or cracks where one side has heaved up or sunk down are red flags.
- Gaps between the slab and walls — this can indicate settlement or movement.
- Pooling water or damp patches — poor drainage can undermine foundations over time.
Walls
- Bowing or leaning walls — stand back and sight along each wall. Any visible lean or bulge warrants further investigation.
- Cracking in cladding or framing — diagonal cracks running from corners of windows or doors often indicate structural movement rather than simple shrinkage.
- Rot or softness in timber framing — probe exposed timber with a screwdriver. If it sinks in easily, the timber may be rotted and structurally compromised.
- Rust staining or corrosion on steel posts or brackets, especially in coastal areas where salt air accelerates corrosion.
Roof Structure
- Sagging roofline — viewed from outside, the ridge line should be straight. Any dip or sag suggests rafter or purlin failure.
- Damaged or missing roof bracing — if you can safely access the roof space, look for broken or disconnected bracing.
- Water stains on the ceiling or rafters — ongoing leaks weaken timber over time.
Doors and Openings
- Garage door that won't sit square in its frame — this can be a sign of frame racking or foundation movement, not just a hardware issue.
- Sticking or binding doors and windows — again, this can point to structural movement rather than just swelling timber.
A Simple Inspection Checklist
| Area | What to Look For | Concern Level |
|---|---|---|
| Concrete slab | Wide or stepped cracks, heaving | High |
| Walls | Bowing, diagonal cracking, rot | High |
| Roof | Sagging ridge, broken bracing | High |
| Cladding | Gaps, cracking, moisture damage | Medium |
| Doors/windows | Racking, won't close square | Medium |
| Drainage | Pooling water near foundations | Medium |
Understanding NZ-Specific Risks
NZ's varied climate and seismic activity create specific risks. In earthquake-prone areas, look for signs of previous movement that may not have been properly repaired — cracked piles, twisted framing, or poorly patched cladding. In high-rainfall regions like the West Coast or Northland, moisture and rot are the bigger enemies. BRANZ publishes useful guidance on building performance in NZ conditions that can help you understand what you're seeing.
If your garage was built before the 1990s, it may have been constructed under older standards and could lack the bracing, fixings, or foundation depth required today under NZS 3604 (the standard for timber-framed buildings).
What You Should NOT Try to Diagnose Yourself
Some things genuinely require professional assessment:
- Whether a crack is structural or cosmetic — this requires knowledge of load paths and building behaviour.
- Foundation depth and condition — you can't see below ground without investigation.
- Whether the building is earthquake-damaged — subtle damage can be invisible to an untrained eye.
- Compliance with the NZ Building Code — only a qualified person can make this call.
When to Call a Professional
If you spot any of the warning signs above — particularly sagging rooflines, bowing walls, wide or stepped cracks, or soft/rotted framing — stop and call a qualified professional before doing anything else. Attempting DIY structural repairs without understanding the cause can make things worse or create safety hazards.
A Licensed Building Practitioner (LBP) or professional building inspector can carry out a thorough assessment and give you a written report. For consent-related or compliance questions, contact your local council. If you're buying or selling a property, a pre-purchase building inspection is strongly recommended.
You can find qualified local building inspectors and LBPs on tradedirectory.co.nz — it's always worth getting someone with local knowledge of your region's specific conditions and common building types.
Important: Any structural repair work on a house or attached garage may require a building consent from your local council. Schedule 1 of the Building Act lists some exemptions, but these are limited — always check with your council before starting work. Visit MBIE Building Performance for guidance on when consent is required.
Licensed Building Practitioner (LBP)
BCITO Qualified
