Cracked Brick Walls
Not every crack is serious — but some absolutely are. Here is how to tell the difference.
Cracks in brick walls are usually caused by foundation movement, rusting steel lintels, failed wall ties, or thermal stress. Hairline cracks that follow mortar joints are often just age. Stair-step cracks wider than 5mm, horizontal cracks, or cracks that are actively growing are the ones to take seriously. The right fix depends on the cause — filling the crack without fixing the underlying cause means it comes back. Romans Building Services assesses cracked brick walls across Sydney before recommending repair, so the visible damage and the cause are both dealt with.
Last updated: 2026-05-29
What is cracked brick walls?
A crack in a brick wall can mean anything from a small cosmetic issue to a serious structural problem. The pattern, width and direction of the crack tell the story. Hairline cracks that follow the mortar joints are usually just age or minor movement. Stair-step cracks that run diagonally through the wall, or cracks that keep widening, are telling you something is moving.
The most common causes in Sydney are foundation movement from reactive clay soils, rusting steel lintels above windows and doors, failed wall ties in cavity brickwork, and thermal or settlement stress in older buildings. Each cause has a different fix. Filling the crack without fixing the cause means it comes back in 6 to 12 months.
Our job is to work out what caused the crack, fix the underlying cause, and then stitch the wall back together properly with a repair that will still be holding 50 years from now.
Signs to look for
- Stair-step cracks running diagonally through mortar joints
- Horizontal cracks — these are more serious than vertical ones
- Cracks that widen or lengthen over weeks or months
- Doors and windows sticking or no longer closing properly
- Cracks wider than 5mm, or ones you can push a coin into
- Gaps opening up between walls and ceilings or floors
- Rust staining above windows (failing lintel)
Why it happens
- Foundation movement — reactive clay soils expanding and contracting with moisture
- Rusting steel lintels pushing the brickwork apart as the steel expands
- Failed wall ties in cavity walls (common in 1960s–80s brick veneer)
- Tree roots displacing footings
- Water damage from leaking pipes or poor drainage softening the ground under the wall
- Original construction defects — undersized footings or poor mortar
How urgent is this?
Hairline cracks along mortar joints can be watched over time. Stair-step or horizontal cracks wider than a credit card, or any crack that is actively growing, should be looked at soon. If doors and windows have started sticking, or if the crack has appeared suddenly after heavy rain, get it assessed now — those are signs of active movement.
How we fix it properly
Diagnose the cause
Before we touch a crack, we work out why it is there. Foundation movement, rusting lintel, failed tie, tree root, drainage issue — the fix depends on the cause. Sometimes we bring in a structural engineer for complex cases.
Stop the cause
If it is a rusting lintel, we replace it. If it is drainage, we fix the drainage. If it is foundation movement from a leaking pipe, we find and fix the leak first. Repairing the wall without stopping the cause is throwing money away.
Helical bar stitching
Stainless steel helical bars bedded into horizontal mortar joints across the crack. They tie the wall back together while letting small future movement happen without re-cracking. A quiet, non-destructive structural repair.
Rebuild or replace damaged bricks
Where bricks are broken or spalled around the crack, we cut them out and replace with matched bricks (reclaimed handmade for heritage, new pressed for modern). The repair blends so you can barely see it.
Repoint and finish
New mortar matched to the existing in colour and profile. On heritage walls, lime mortar. On modern, appropriate cement mix. Finished so the wall looks right.
Typical cost range
$800 – $8,000 for typical domestic crack repairs. Major structural work with engineer involvement can run $15,000+.
Every job is different. We give a firm quote after inspection.
Common questions
How do I know if my cracked wall is dangerous?
Width over 5mm, horizontal orientation, or cracks that are actively growing are the warning signs. If you can see daylight through the crack, or if the wall is bulging out of line, call someone that day. For smaller cracks, monitor them over a few weeks to see if they are stable or still moving.
Will filling the crack with sealant fix it?
Only if the cause has been fixed. Otherwise the crack just opens up again beside the sealant. We often see old caulked repairs that have failed — the original crack is still there, with new cracks either side of the sealant. Fix the cause first.
What is helical bar stitching and is it invisible?
Helical bars are stainless steel spiral rods bedded into the horizontal mortar joints. After repointing, they are completely hidden. They hold the wall together across a crack while allowing minor future movement without re-cracking. One of the best structural repair techniques for brick.
Do I need a structural engineer?
For most typical cracks, no. We can diagnose and repair within our scope. For major structural issues — footing failure, wall replacement, significant movement — yes, and we work with engineers regularly. We will tell you up front if yours is one of those cases.
Services that fix this
Cracked Brick Walls in your area
The causes and right fix for cracked brick walls vary with local housing stock and exposure. Read the version closest to where you are:
Where we see cracked brick walls most often
Some suburbs have more of this problem than others — the local housing stock, age, and coastal exposure all play a part. Click through for the local context.
Think you might have cracked brick walls?
Send a photo or call Minas directly. We will tell you straight whether it needs doing now, or whether it can wait.