Lintel Rust Above External Window
Steel lintels above external windows corrode when protective coatings fail or moisture reaches bare metal, causing the steel to expand as it oxidises. The expansion exerts lateral pressure on the brick courses above, leading to cracking in the masonry. Left unaddressed, the lintel may lose structural capacity, making the brickwork above the window opening unstable.
Severity rationale
Across 616 observations the modal score is 3, recorded in 384 cases (62.3%). Scores of 2 account for 199 findings (32.3%), and the average sits at 2.76, confirming this is predominantly a moderate-severity defect. Only 32 observations (5.2%) reached a 4 or 5, which typically correspond to advanced corrosion with active cracking and structural loss. The lower scores reflect early-stage surface rust that is straightforward to treat; the score climbs when the lintel has expanded noticeably and brick cracking is visible and widening.
Causes
- Loss of protective paint or galvanising coating exposing bare steel to moisture
- Prolonged weathering and UV exposure degrading factory-applied coatings
- Water tracking behind render or cladding and pooling at the lintel bearing
- Age-related coating breakdown on uncoated or under-specified lintels in older homes
- Moisture ingress through failed window head flashings or sill junctions
Symptoms to look for
- Visible orange or brown rust staining on the face of the lintel or on the wall below
- Hairline to moderate cracks in brick courses immediately above the window opening
- Paint or render blistering and flaking adjacent to the lintel
- Rust streaking running down the external wall face from the lintel position
- Spalling or displaced mortar at the lintel-to-brick interface
Remedies
- Engage a licensed painter to grind back rust, apply rust converter, and re-coat with a compatible metal primer and topcoat
- Engage a bricklayer to repoint or rebuild cracked courses above the lintel once the corrosion is treated
- Assess and repair any failed window head flashing or sealant allowing water to track to the lintel
- Where the lintel is extensively corroded and structurally compromised, engage a structural engineer to assess and specify replacement
Where we see this most
These suburbs show the highest concentration of lintel rust above external window in our inspection data (minimum five observations). Click a suburb to see its full defect profile.
Worth asking our inspector about this specifically.
Surface rust without cracking can be treated as a maintenance item at the next trade visit. Where cracking above the window is visible and growing, engage a bricklayer to assess before it progresses to a structural concern.