A lintel is a structural support that sits above an opening in a wall — usually a window or a door. Its job is simple: carry the weight of the wall above so that the opening below doesn’t collapse or deform. Most openings need one, and in most houses, they’re easy to miss because they’re either built into the wall or hidden behind finishes.
There are several types of lintels. In older homes, it might be a timber beam, a stone slab, or even a segmental brick arch. In mid-century builds, you’ll often find concrete or steel. In modern cavity wall construction, a single galvanised steel lintel is typically used to support both the inner and outer leaves of the wall. These are known as cavity wall lintels, and they’re usually designed with insulation to reduce cold bridging across the cavity.
So why do lintels fail?
Over time, timber lintels can rot, especially if embedded in damp masonry. Brick arches can slump or lose their shape. Steel can rust and expand. And concrete can crack or spall, particularly if poorly made or exposed to water over time. But most of the time, failure is not about the lintel itself disintegrating — it’s about the wall above showing signs that the lintel is no longer doing its job properly.
Here are the signs surveyors look for — and that you can look for too:
- Cracks above window or door openings, especially diagonal cracks from the top corners. These are often the first sign that a lintel is sagging or not supporting the wall as intended.
- Brickwork drooping or bowing above an opening. If the bricks look like they’ve settled or stepped downward in a curve, that suggests movement or compression — sometimes due to a missing lintel altogether.
- Gaps between the window frame and masonry. In cavity walls, if the outer lintel fails, the masonry can start to lean on the window or door frame. Over time, this pressure can distort the frame, making it hard to open or close, and forming visible gaps.
- Rust staining or spalling concrete. If you see rust marks bleeding through render or brick, or pieces of concrete falling away, that can be a sign of steel lintel corrosion or concrete degradation.
- Render cracking in bands above windows and doors, particularly horizontal or stepped cracking, can often be traced back to lintel issues — especially where patch repairs have already been attempted.
The important thing is not to ignore these signs.
A failing lintel won’t always lead to a major collapse, but it will cause progressive damage to the wall if left unchecked. It can also lead to water ingress if cracks widen or the brickwork deforms. And in the worst cases, it compromises the structural integrity of the elevation.
What we always recommend is that when changing doors and windows, the contractor takes the opportunity to check the condition of lintels, as this is the best time to replace them where needed.
Professional surveys often start as non-invasive, meaning surveyors have to look for the same signs as above and can only confirm lintel construction where clearly visible. Concrete lintels are often exposed and relatively easy to identify.
At Survey Shack, we show you how to identify movement patterns which suggest lintel failure. We flag the issue so the right investigation can follow. If the windows are in poor condition, or you’re looking to replace or extend the property, this is a great time to tackle such issues. Consulting a competent builder and structural engineer for repair costs to the masonry itself is also wise, depending on the severity.
Defective lintels and associated masonry damage are fixable.
But knowing when to look further is key — especially if you’re buying or selling. Because if the wall above a window is starting to tell a story, the lintel is usually the opening line.
Looking for a “surveyor near me”? The closest one is in your pocket. Survey Shack helps you inspect a property and decide if you need a homebuyers survey, a full building survey, or a residential structural engineer. Smart, low-cost insight for today’s buyers, sellers, and property professionals.
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