Every crack has a cause
Buildings crack for a reason, and the reason decides the repair. Fill a crack caused by a rusting lintel and the steel keeps expanding until the crack reopens. Patch a crack caused by footing movement and it splits again next dry summer. That's why our first step is always diagnosis: the crack pattern, location, width and how it's changing tell us a lot about the cause.
We repair cracks in brick and block walls, render, internal plaster and concrete for Sydney homes and strata buildings, and we coordinate with structural engineers whenever the cause is structural.
Types of cracks and what they mean
| Crack pattern | Common cause | Typical repair |
|---|---|---|
| Hairline cracks in plaster or render | Shrinkage, minor seasonal movement | Cosmetic repair and repaint |
| Stair-step cracks through mortar | Footing movement, reactive soil | Cause investigation, crack stitching, possibly underpinning |
| Cracks above windows and doors with rust | Corroding steel lintel | Lintel replacement |
| Horizontal cracks in brick courses | Corroded wall ties, roof thrust | Wall tie replacement |
| Vertical cracks at corners or long walls | Thermal or moisture movement, no control joints | Stitching, control joints |
| Cracking render with drummy patches | Moisture, salt, poor bond | Render repair |
Crack stitching
Crack stitching uses stainless steel helical bars bonded into slots cut in the mortar joints across the crack. The bars tie the cracked brickwork back together and spread load across the wall. Once installed, the joints are repointed to match the existing mortar, so the repair is barely visible.
- Suits stair-step, vertical and diagonal cracks in brick and block walls
- Minimal disruption with no large-scale demolition
- Repointed to match existing joints
- Used after the cause has been fixed or confirmed as stable
Lintel replacement
Many older Sydney homes have mild steel lintels over windows and doors. When moisture gets to them, the steel rusts and expands, lifting the brickwork above and causing cracks, bowed brick courses and rust stains. Left alone, the brickwork can drop.
We temporarily support the brickwork, remove the bricks above the opening, replace the old lintel with a galvanised or stainless lintel and flashing, rebuild the brickwork with matching bricks and mortar, and repair any internal damage.
Wall tie replacement
In cavity brick homes, metal ties hold the outer brick skin to the inner wall. Older ties corrode, especially near the coast, and the outer skin can crack horizontally, bulge or separate. We install stainless steel retro-fit ties from outside, disconnect or remove failed ties where needed, and repair the cracked brickwork.
Not sure if it's serious?
Send us photos with something for scale. We'll tell you whether it looks cosmetic or needs a proper assessment.
Our crack repair process
- Inspect and mapWe record crack locations, widths and patterns and look for related signs.
- DiagnoseIdentify the likely cause, and bring in a structural engineer where needed.
- Fix the causeLintels, wall ties, drainage, roof thrust or footings.
- Repair the crackStitching, rebuilding, repointing or render repair.
- Make goodInternal plaster, cornices, paint and doors adjusted.