What is it?
Cracks appearing in the masonry or plaster directly above a window opening.
What does it look like?
[Insert Photos] Often diagonal “stepped” cracks in brickwork or vertical cracks in plaster above the window frame.
Common causes
1. Corroded or failing lintels
2. Foundation settlement
3. Thermal movement
4. Window replacement without proper support
How serious is it?
Rating: High Concern. Cracks above windows often point to lintel failure, which can lead to localized collapse of masonry if ignored.
How to tell which cause you have
Check if the window pane is cracked or if the frame is bowing. These are strong signs of lintel failure.
What should you do next?
Check the exterior for signs of “blown” bricks. Contact a builder or surveyor to inspect the lintel.
Typical repair options
Installing a new steel lintel, masonry reinforcement, or repointing.
Typical repair costs (UK)
£400 – £2,000 per window.
Frequently Asked Questions
1. Why do window cracks happen after new windows? Lack of temporary support.
2. Is it subsidence? Possibly, if cracks are wide.
3. Can I just fill it? Not if the lintel is failing.
4. Are wooden lintels bad? They rot over time.
5. What is a soldier course? A row of vertical bricks often prone to sagging.