Lintel failure: signs and replacement

A lintel is the beam that carries the wall over a window or door opening, and lintel failure is when it rots, cracks, corrodes or sags so it no longer supports the masonry above properly. The usual signs are cracks running up from the corners of the opening, sagging brickwork and windows or doors that stick, and the fix is usually a replacement lintel.

What does a lintel do?

A lintel carries the weight of the wall, and sometimes floors or a roof, over a window or door opening, passing the load down into the masonry on each side. Its ends sit on bearings built into the wall either side of the opening. If the lintel weakens, or its bearings are too short or crumbling, the brickwork above starts to drop into the opening. Older houses may instead have a brick arch, or a timber lintel hidden behind the outer brickwork.

What are the signs of a failing lintel?

The commonest sign of a failing lintel is cracking in the brickwork or plaster just above an opening, often stepping up from one or both top corners. A lintel can fail at one end only, so cracks may show on one side. Check the plaster inside as well as the brickwork outside, because many cavity walls have a separate lintel for each leaf. Several signs together, or signs that are getting worse, suggest the lintel should be inspected soon.

• Stepped cracks rising from the top corners of an opening
• Brickwork above the opening sagging or dropping
• Windows or doors starting to stick or bind
• Rust staining or flaking steel above an opening
• Cracked, spalling concrete with exposed reinforcement
• Soft or crumbling timber where it is visible

How do timber lintels fail?

Timber lintels usually fail through rot or insect attack. They are common in older houses, sometimes only on the inner leaf or behind a brick arch, and they last well while dry. Damp from leaking gutters, failed pointing or condensation lets wet rot set in, and woodworm can weaken timber further. A rotten lintel can compress and sag, letting brickwork drop. Because timber is often hidden, the first sign may be a crack or a soft spot when you press a screwdriver into it.

How do concrete and steel lintels fail?

Concrete lintels usually fail when the steel reinforcement inside them rusts. Water reaches the steel through cracks or thin cover, and the rust expands, splitting the concrete and pushing off pieces, a process called spalling. Steel lintels fail by corroding, particularly where the protective coating has worn away. Rust expands as it forms and can lift the brickwork above, which is sometimes called rust jacking. Both types can also fail because the bearings were too short, or because the wall around them has moved.

Could the crack be caused by something else?

Yes, cracks above windows and doors are not always caused by the lintel. Subsidence often shows first at openings, because they are the weakest points in a wall, giving diagonal cracks that run beyond the opening. Wall tie corrosion gives horizontal cracking, and a sagging floor or roof can load an opening unevenly. If cracks extend well past the opening, or appear at several openings, get the cause checked. If subsidence is possible, tell your insurer before permanent repairs start.

How is a lintel replaced?

Replacing a lintel usually takes 1 to 2 days for a standard opening. First the wall above is propped with temporary steel props and supports passed through the brickwork, so it is held while the old lintel comes out. The brickwork directly above the opening is carefully removed, the old lintel is taken out, and a new lintel of the right size and type is bedded on sound bearings. The brickwork is rebuilt to match, with any cavity tray and weep vents needed, and the inside is made good.

How much does lintel replacement cost?

Lintel replacement over a standard window or door opening is a guide £750 to £2,500 inc VAT. A wide or bay opening is about £2,000 to £4,500, and making good inside and out about £150 to £600 per opening. Where a brick arch needs rebuilding instead, one side is about £900 to £1,300. Replacing a lintel is structural work, so building control is often involved in England and Wales; check before work starts. Prices vary by region and access and are confirmed in writing after a survey.

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