Most brick walls develop cracks at some point — it's a normal part of a building's life. The key question is whether a crack is simply a cosmetic blemish caused by minor movement or weathering, or a warning sign of something more serious going on with your home's structure. Here's how to read the signs.
Start With a Close Visual Inspection
Before you panic, grab a torch, a tape measure, and a piece of chalk. Mark the ends of any crack with the date so you can monitor whether it grows over time. Look carefully at:
- Width — hairline cracks under 1 mm are usually cosmetic; cracks wider than 3–5 mm deserve closer attention
- Length and pattern — short, isolated cracks differ from long cracks that run continuously across multiple bricks and mortar joints
- Direction — horizontal, diagonal (stair-step), or vertical cracks each tell a different story (see below)
- Depth — does the crack go all the way through the wall, or is it surface-only?
- Displacement — is one side of the crack higher or further out than the other? Any stepping or bulging is a red flag
What the Crack Pattern Tells You
| Crack Type | Typical Appearance | Likely Cause | Concern Level |
|---|---|---|---|
| Hairline vertical | Thin, straight, in mortar joints | Thermal expansion/shrinkage | Low — usually cosmetic |
| Stair-step diagonal | Follows mortar joints in a staircase pattern | Differential settlement | Moderate to high |
| Horizontal | Runs along mortar joints, often mid-wall | Soil pressure, wall tie failure | High — seek advice |
| Wide diagonal | Large, tapered crack, often near openings | Foundation movement | High |
| Crack around window/door | Radiates from corners of openings | Lintel movement or settlement | Moderate to high |
Stair-step cracks are one of the most common patterns in NZ brick veneer homes. A small stair-step crack that hasn't changed in years is often benign, but a widening or lengthening one needs investigation.
Horizontal cracks are the most serious. They can indicate that the wall is being pushed inward by soil pressure (common in retaining walls) or that wall ties — the metal connectors between the brick veneer and the timber frame — have corroded and failed. Wall tie failure is a known issue in NZ homes built from the 1940s through to the 1980s, where galvanised ties have had time to rust.
Active vs. Dormant Cracks
One of the most important distinctions is whether a crack is active (still moving) or dormant (stable). Use your chalk marks and check back every few weeks. You can also press a small dab of plaster or filler across the crack — if it breaks again, the crack is still moving.
Active cracks always warrant professional assessment. Dormant hairline cracks in mortar joints are often simply repointed and left at that.
NZ-Specific Factors to Consider
New Zealand's geology and climate add some unique considerations:
- Earthquake damage — even minor seismic events can cause brick veneer cracking. If cracks appeared after a quake, treat them as potentially structural until assessed. Check guidance from MBIE Building Performance on post-earthquake building assessment.
- Expansive clay soils — common in parts of Auckland, Hawke's Bay, and Canterbury. These soils shrink in dry summers and swell in wet winters, causing cyclic foundation movement.
- NZ Building Code compliance — brick veneer construction in NZ is governed by NZS 3604 (timber-framed buildings) and the Building Code clauses around structure (B1) and weathertightness (E2). Significant cracking may indicate non-compliance that needs remediation.
- Healthy Homes and rental properties — if you're a landlord, structural issues affecting weathertightness can also have implications under Tenancy Services Healthy Homes standards.
BRANZ is an excellent NZ resource for understanding how brick veneer systems perform and what constitutes acceptable movement.
Simple DIY Checks You Can Do
- Check inside as well as outside — does the crack correspond with interior cracking in the plasterboard or GIB lining? Interior cracking alongside exterior brick cracking increases the likelihood of structural movement.
- Look at doors and windows — are they sticking, jamming, or sitting out of square? This can indicate frame distortion from foundation movement.
- Inspect the foundation — if accessible, look for cracking or crumbling at the base of the wall or in the concrete foundation.
- Check the roofline — a sagging or uneven roofline seen from the street can indicate significant structural movement.
When to Call a Professional
You should contact a licensed building practitioner (LBP) or a structural engineer if you notice any of the following:
- Cracks wider than 5 mm or that are visibly growing
- Horizontal cracks anywhere in a brick wall
- Bulging, bowing, or leaning sections of brickwork
- Cracks accompanied by sticking doors/windows or sloping floors
- Any cracking that appeared suddenly or after an earthquake
- You're buying or selling a property with visible brick cracking
A structural engineer can carry out a proper assessment and, if needed, specify repairs. For wall tie failure specifically, a specialist remediation contractor will be required. Building consent may be needed for structural repairs — always check with your local council first. You can find qualified bricklayers and building professionals in your area on tradedirectory.co.nz.
For LBP verification, visit Licensed Building Practitioners.
Sources & Further Reading
- MBIE Building Performance — Building Code and guidance
- BRANZ — Building research and technical guidance
- Licensed Building Practitioners — Find or verify an LBP
- Standards NZ — NZS 3604 and other building standards
- Tenancy Services — Healthy Homes Standards
- WorkSafe NZ — Safety when working at height or near structures
Licensed Building Practitioner (LBP)
