Stepped cracks in brick walls, those zig-zag lines that travel diagonally up through the mortar joints, are the most recognisable sign of foundation movement in a brick home. Unlike cracks that run straight through the brick itself, stepped cracks follow the weakest line in the wall, which is always the mortar between the courses. They are worth taking seriously, but the pattern, direction and width all tell you something specific before you call anyone. This guide explains how to read them and when to book a foundation inspection.
Why brickwork cracks in steps and not straight lines
Brick is much stronger than mortar. When a wall is placed under differential stress from movement below, the stress travels through the weakest path, which is the bond line between each course of bricks. The crack finds its way diagonally by alternating between horizontal and vertical mortar joints, producing the characteristic staircase or zig-zag pattern.
A crack that runs straight through the brick face rather than along mortar lines is typically a sign of much greater force, such as an impact or a severe structural load. Stepped mortar cracks are almost always movement-related rather than impact-related, and in Wagga homes on reactive clay the source is usually the soil shifting beneath the footings. The broader context of why this happens is covered in our cracks in walls guide.
Cracks widening at the top versus at the bottom
The direction of a stepped crack and where it is widest tells you something about what is happening below.
Wider at the top: The base of the wall at that point has dropped while the upper section is still supported. This is classic settlement: one part of the footing has sunk into the ground, pulling the brickwork downward on that side and leaving the top section unsupported and opening.
Wider at the bottom: The base of the wall at that point has been pushed upward while the upper section has not moved. This is heave: the soil is expanding under one section of the footing, lifting it relative to the rest of the structure. Heave is less common than settlement in Wagga but does occur after heavy rainfall following a drought, or when a large tree is removed and the clay rehydrates.
Consistent width along the full length: This can indicate an older crack that has since stabilised, or a slow uniform settling movement. Consistent-width cracks that are no longer growing may be historical rather than active.
These are indicators, not diagnoses. The actual cause requires professional inspection and cannot be determined from crack pattern alone. See the cracks above door frames guide for the typical crack pattern that appears specifically at window and door openings.
Where stepped cracks show up in Turvey Park and Kooringal
Wagga’s older brick suburbs see stepped cracks more often than newer areas, for straightforward reasons. The homes are older, the footings were often built to earlier standards, and decades of reactive clay movement have had more time to accumulate.
In Turvey Park, many homes are double-brick construction from the 1950s to 1970s. These were typically built on strip footings that were engineered for the expectations of the time. On the highly reactive clay that underlies much of this suburb, fifty years of drought-flood cycling has placed significant cumulative stress on these footings. Stepped cracks at the corners of external walls and above windows are common findings in pre-purchase inspections in this area.
In Kooringal, the housing stock is broadly similar in age and includes many brick veneer homes with single-brick external skins tied back to a timber or steel frame. Brick veneer is more flexible than double-brick and can accommodate some movement without cracking, but significant foundation movement still produces stepped cracks in the veneer, particularly at the corners of the structure where movement concentrates.
Gaps appearing at the skirting boards inside these homes often accompany exterior stepped cracks. If you are seeing both, see our gaps between skirting and floor guide alongside this one.
Photograph, measure, monitor
Before calling a professional, set up a basic monitoring record. This takes five minutes and gives you genuinely useful data.
- Photograph each stepped crack clearly, with a ruler or coin in frame for scale
- Note the date in the photo or file name
- Mark the ends of the crack on the wall with a pencil cross and write the date beside it
- Measure the widest point of the crack and record it alongside the mark
- Re-photograph and re-measure every four to six weeks
What you are looking for: a crack that has not grown in three months is more likely to be historical or slow-moving. A crack that has grown by 2 mm or more in six weeks is active and warrants prompt inspection. A crack that has changed direction or spawned secondary cracks nearby is also a concerning sign.
Repair options: from repointing to underpinning
The right repair depends on whether the underlying movement has been arrested or is still occurring.
Repointing: Raking out and replacing the cracked mortar is a cosmetic repair appropriate only once the cause has been addressed and movement has stopped. Repointing active cracks will fail within months as the movement reopens them.
Crack stitching: A structural repair technique that installs stainless steel ties across the crack to stitch the wall back together and prevent further separation. Used for cracks that have stabilised or where the footing movement has been addressed.
Foundation crack repair: Specialist repair that addresses the crack structurally, sometimes using epoxy injection or tie-bar systems. Our foundation crack repair service covers the full scope of what this involves.
Underpinning: When the crack is caused by active footing movement that will continue without intervention, the footing itself needs to be stabilised. Our underpinning service addresses the cause; cosmetic repair of the crack follows after the structure has been stabilised and given time to settle.
How much brick crack repair usually costs
The following ranges are indicative patterns for the Wagga region and are not quotation prices.
| Repair type | Appropriate when | Indicative cost range (AUD) |
|---|---|---|
| Mortar repointing | Movement has stopped; cosmetic repair only | $500 to $2,500 |
| Crack stitching | Structural stabilisation of stable or arrested crack | $1,500 to $5,000 |
| Foundation crack repair | Active crack with underlying movement addressed | $2,000 to $8,000+ |
| Underpinning (where required) | Active footing movement causing the crack | See underpinning cost guide |
These figures assume access is straightforward and the work is limited to the visible cracking. If underpinning is required, the foundation repair is the major cost driver and the crack repair is a secondary scope item that typically follows after stabilisation.
FAQs
Are all stepped cracks in brick walls caused by foundation movement?
Most stepped cracks in mortar joints are related to differential movement somewhere in the structure, whether that is the footing, the sub-floor support, or differential thermal movement. Very fine hairline cracks in mortar are sometimes the result of original construction shrinkage and may be stable. Wide, stepped cracks that have clearly opened, or that have changed over time, should be assessed by a professional.
How wide does a stepped crack have to be before it is serious?
As a rough guide: hairline cracks up to about 0.2 mm are very low concern. Cracks between 0.5 and 2 mm are worth monitoring. Cracks over 2 mm, particularly if they show displacement (one side of the crack higher than the other), should be professionally assessed. Displacement in any crack, regardless of width, is a significant indicator of structural movement.
Can I just patch stepped cracks myself?
You can patch the mortar cosmetically, and this is fine if you are confident the movement has stopped and you are treating the repair as decorative. Patching cracks that are still moving is generally a waste of money: the new mortar will crack again within a year. Address the cause before the crack.
How do I know if my stepped crack is getting worse?
The monitoring protocol above is the practical answer: mark the ends, measure the width, photograph regularly. If you would rather have a simple quick check, stick a small strip of paper tape across the crack. If the tape tears within a few weeks, the crack is still moving.
Do stepped cracks affect the resale value of my home?
Yes, they typically do, particularly if there is no professional report confirming the cause and status. An engineer’s report that says the crack is historical, monitored and stable is far better for resale than leaving it unexplained. Our foundation inspections service produces the kind of written assessment that satisfies both buyers and conveyancers.