Not every crack above a window in a Wagga Wagga home is a foundation-movement crack. A specific and easy-to-miss cause sits right above the glass itself: a corroding steel lintel or a shifted brick arch, expanding as it rusts and physically jacking the brickwork above it apart, with nothing happening at footing level at all. Confusing this with reactive-clay settlement cracking means paying for the wrong repair. This guide explains how to tell the two apart and what fixes each one.
Two very different causes, one crack location
Cracks above windows get a lot of coverage on this site as a foundation-movement symptom, and rightly so: diagonal cracks radiating from the top corners of an opening are a classic sign of a footing dropping or heaving on one side, as covered in our guide to foundation crack types: serious vs cosmetic. But there’s a second, entirely separate mechanism that produces cracking in almost exactly the same location, and it has nothing to do with the ground under the house.
Lintel corrosion, sometimes called “rust jacking”. Most brick veneer homes built from the 1960s onward use a galvanised steel angle lintel to bridge the masonry above a window or door opening. Where the galvanising has worn through, or where the lintel wasn’t adequately protected to begin with, moisture (from a failed damp-proof course, a blocked weep hole, or just decades of weather) corrosifies the steel. Rusting steel expands to several times the volume of the original metal, and that expansion physically pushes the brick course sitting directly on top of the lintel upward and outward.
Brick arch movement. Older homes, particularly Federation and inter-war construction common around Turvey Park and Central Wagga, sometimes use a brick soldier or segmental arch above a window instead of a steel lintel. These arches rely on the bricks wedging against each other in compression. Where mortar has deteriorated, or where the wall either side of the arch has shifted (from footing movement or otherwise), the arch can lose its keying action and crack or drop slightly at the crown.
Both of these produce a crack roughly along the top of the window opening, which is exactly where a footing-driven diagonal crack often finishes too. That overlap is the trap.
Reading the difference
A handful of details separate a lintel or arch problem from footing movement:
- A horizontal crack running the full width of the lintel, sitting just above the steel angle or the arch, with no diagonal component, points strongly toward corrosion jacking or arch movement rather than settlement.
- Rust staining bleeding through the mortar or paint directly above the window, sometimes visible as an orange-brown tide mark, is close to a confirmed sign of a corroding lintel.
- The brick course immediately above the opening sitting slightly proud of the coursing either side, as if it has been physically pushed up, is characteristic of rust jacking rather than settlement.
- A diagonal crack running up and away from one top corner of the opening, with no horizontal component along the lintel line itself, is the classic footing-movement pattern covered in our guide to cracks in walls: when to worry.
- Symptoms elsewhere in the house, sticking doors, sloping floors, cracking at other openings on the same wall, support a footing-movement diagnosis; a lintel or arch issue confined to one window with no other symptoms in the house points the other way.
It’s genuinely possible to have both at once, particularly in an older home: a corroding lintel above one window and ordinary reactive-clay cracking elsewhere on the same wall. That’s exactly why reading the pattern in isolation isn’t enough, and why a proper inspection looks at the whole wall rather than one crack.
Why the wrong diagnosis costs you twice
If a corroding lintel is mistaken for footing movement, a homeowner may pay for underpinning that does nothing to address the rusting steel above the window, and the crack keeps opening regardless of what happens at footing level. Conversely, if genuine footing-driven cracking above a window is dismissed as “just an old lintel” and simply repointed, the crack reopens as the underlying movement continues, and worse, no one has checked whether the movement is worsening.
A foundation inspection is the sensible starting point either way. Part of that inspection process involves checking whether cracking correlates with floor level changes, drainage issues or sticking doors elsewhere in the house (pointing to footing movement) versus being isolated to one opening with visible corrosion or arch displacement and no other symptoms (pointing to a lintel or masonry issue specific to that opening).
What repair involves for each cause
Corroded lintel replacement. Where a steel lintel has corroded significantly, the affected section of brickwork above the window is carefully propped and supported, the old lintel is removed, and a new galvanised (or stainless, in more exposed situations) lintel is installed with adequate cover and a functioning damp-proof course above it. The brickwork is then reinstated and repointed to match. Where corrosion is caught early and is only cosmetic surface rust with minimal section loss, treating and repainting the exposed steel plus repointing the affected joint may be sufficient; a tradesperson experienced in this specific defect can tell the difference on site.
Brick arch repair. A displaced or cracked masonry arch is typically repaired by carefully removing and rebuilding the affected arch section, addressing whatever caused the original movement (often repointing degraded mortar, sometimes correcting a footing issue on the wall below first), and reinstating with matched bricks and mortar profile.
Footing-driven cracking above a window. Where the diagnosis points to genuine footing movement rather than a lintel or arch defect, the sequence follows the same path as any other structural crack: the underlying movement is addressed first (commonly underpinning, or drainage correction on a milder case), and foundation crack repair makes good the masonry afterward.
In every case, filling and painting over the crack without identifying which of these is actually happening is the single most common mistake, because the crack simply reopens along the same line once the underlying cause (rust expansion, arch displacement, or footing movement) continues.
Lintel and brick arch crack FAQs
How do I know if my window lintel is rusting without pulling the wall apart?
Look for a horizontal crack running the width of the lintel, rust staining bleeding through paint or mortar directly above the opening, and a brick course that sits slightly proud of the coursing either side. Any combination of these is worth having assessed rather than just repainted over.
Is a rusting lintel urgent?
It’s rarely an emergency, but it doesn’t improve with time either: corrosion is progressive, and the longer it continues, the more brickwork gets disturbed and the larger the eventual repair. Getting it assessed sooner rather than later generally keeps the job smaller.
Can a corroding lintel actually cause the wall to fail?
In advanced, long-neglected cases, ongoing expansion can displace enough brickwork to become a genuine structural concern, but this typically takes many years of untreated corrosion to reach that point. Most cases are caught well before then when addressed on reasonable notice.
Does home insurance cover lintel corrosion repairs?
This varies significantly by policy, and gradual corrosion or wear-and-tear style damage is commonly excluded by insurers, unlike sudden events. Check your specific policy; a written assessment of the cause helps if you do need to make a claim.
My crack is above a window with a brick arch, not a steel lintel. Does the same logic apply?
Largely yes: a horizontal or crown crack confined to the arch, with no diagonal component and no other symptoms in the house, points toward arch or mortar deterioration rather than footing movement. Older arches also age simply from mortar breakdown over many decades, independent of any corrosion mechanism.
Should I get an engineer involved?
For genuine footing-movement cracking, yes, usually as part of the broader inspection process. For a straightforward corroded lintel with no other symptoms in the house, an experienced builder or foundation specialist can typically diagnose and quote the repair without a separate engineering report, though your contractor will flag it if the situation looks more complex than a standard lintel replacement.
Get your window cracking properly diagnosed
Cracking above a window can mean a rusting lintel, a tired old brick arch, or genuine footing movement, and treating the wrong one wastes money either way. Get a free quote and an independent licensed contractor can look at the actual cause before recommending any repair.