Lintels support masonry over windows and doors. Cracking that rises diagonally from an opening, dropped brickwork or distortion can indicate inadequate, corroded or altered support, but similar cracks may have other causes. A competent inspection should identify the lintel type and movement before repair.
When this guide fits
Clues worth recording
- Diagonal cracks from window or door corners
- Dropped or stepped masonry over an opening
- Rust staining or spalled masonry
- A replacement window with little visible support
Why openings are vulnerable
Removing masonry for a window or door interrupts the normal load path. A lintel bridges the gap. Older construction, corrosion, alterations or replacement frames can reveal or create inadequate support.
Lintel cracks versus wall tie cracks
Lintel-related movement often concentrates around an opening, while tie corrosion may create longer horizontal cracks along mortar beds. Real walls can have more than one defect, so pattern recognition must be checked against the construction.
What an inspection should establish
The inspector should consider the lintel material and bearing, movement pattern, cavity details, wall ties near the opening and any window replacement history. Opening up may be needed where support is concealed.
Loose masonry over a door or window can pose a falling-debris risk. Restrict access and seek prompt professional advice.
Repair scope
Depending on the finding, work may involve installing or replacing a lintel, local rebuilding, corrosion treatment, crack repair and making good. Temporary support and sequencing are safety-critical contractor matters.
Questions homeowners ask
What people usually want to know
Do uPVC windows support the brickwork?
A window frame should not be assumed to replace a properly designed lintel. Construction varies, so inspect the actual opening.
Can a lintel be repaired without removing the window?
Sometimes, depending on construction and the selected system. A specialist should define access, temporary support and sequencing.
Is rust staining proof of lintel failure?
No, but it is useful evidence. Other embedded steel and fixtures can also corrode.
Sources & review
Evidence behind this guide
Reviewed 1 September 2026. We use primary guidance where available and label trade-body advice clearly.