Yes, as a homeowner you can identify many of the visible warning signs of subsidence yourself — and doing so early can save you significant money and stress. However, confirming the cause, extent, and required remediation always needs a qualified professional. Here's what to look for and how to approach it safely.
What Is Subsidence?
Subsidence is the gradual sinking or settling of the ground beneath your home's foundations. In New Zealand, it can be caused by a range of factors including expansive clay soils drying out, poor drainage, tree root activity, erosion, historic fill material, earthquake damage, or inadequate original foundations. Some areas of NZ — particularly parts of Auckland, Wellington, Hawke's Bay, and Canterbury — have soils or histories that make subsidence more likely.
Visual Signs You Can Check Yourself
A careful walk around and through your home can reveal a lot. Look for the following warning signs:
Outside the House
- Cracks in exterior cladding or brickwork — diagonal cracks running from the corners of windows or doors are a classic sign of differential settlement
- Gaps between the wall and window or door frames that weren't there before
- Uneven or sloping paths, driveways, or decks adjacent to the house
- Visible gaps between the foundation (piles or concrete perimeter) and the floor framing above
- Leaning or bowing walls when viewed from a distance
- Separation between the house and any attached structures like garages or decks
Inside the House
- Doors and windows that stick, jam, or no longer close squarely — this is often one of the first signs homeowners notice
- Sloping or bouncy floors — place a marble or spirit level on the floor to check
- Cracks in interior plasterboard or GIB lining, especially diagonal cracks at corners of openings
- Gaps between skirting boards and the floor, or between the ceiling cornice and wall
- Cracked or lifting floor tiles
Under the House (Subfloor)
If your home has a subfloor crawl space, a careful inspection (with a torch and appropriate protective gear) can be very revealing:
- Piles that are leaning, cracked, rotting, or have sunk into the ground
- Bearers or joists that are no longer level or are pulling away from piles
- Pooled water or consistently damp soil beneath the floor — ongoing moisture can cause soil movement and timber decay
- Cracked or crumbling concrete foundations
- Evidence of past repairs that may not have addressed the root cause
Safety note: Before entering a subfloor space, check for adequate ventilation, no signs of gas leaks, and watch for sharp objects, asbestos-containing materials (common in homes built before the 1990s), and unstable framing. If in doubt, don't enter — call a professional.
Using a Simple Level Test
A long spirit level or a laser level is a handy DIY tool. Place it across floors in multiple rooms and note any consistent slope. A noticeable consistent slope can indicate a problem worth investigating, though some older NZ homes have always had minor unevenness. What matters most is change over time — take photos and measurements and check again in a few months.
What Doesn't Always Mean Subsidence
Not every crack or sticky door is a sign of serious subsidence. NZ homes naturally move with seasonal temperature and humidity changes, especially timber-framed houses. Hairline cracks in plasterboard are common and often cosmetic. The key red flags are:
- Cracks that are widening over time
- Multiple signs appearing together
- Cracks wider than about 3–5 mm
- Any structural movement you can feel underfoot
| Sign | Likely Concern Level |
|---|---|
| Hairline plasterboard cracks | Low — monitor |
| Sticking doors (one only) | Low–Medium — investigate |
| Diagonal cracks at window corners | Medium — get inspected |
| Sloping floors + sticking doors + exterior cracks | High — urgent inspection needed |
| Visible pile movement or foundation cracking | High — urgent professional assessment |
When to Call a Professional
If you spot multiple warning signs, or any signs that appear to be worsening, it's time to call in expert help. A Licensed Building Practitioner (LBP) or a registered building inspector can carry out a thorough assessment of your home's structure. For anything involving foundation design or significant ground movement, you'll also want a geotechnical or structural engineer involved.
Remediation work on foundations — such as re-piling, underpinning, or drainage improvements — will often require a building consent from your local council. Always check with your council before starting any structural work, as requirements vary. You can find guidance on what requires consent at MBIE Building Performance.
If your home was built before the 1990s, be aware that subfloor materials may contain asbestos. WorkSafe NZ has guidance on identifying and managing asbestos safely.
You can find qualified local building inspectors and tradespeople on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
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