Above every door and window in a masonry wall sits a small beam called a lintel. Often there is also a thin projecting slab called a chajja. They are easy to overlook, but they prevent cracks above openings and keep rain and sun out of your rooms.
What a lintel does
When you cut an opening in a wall, the bricks above it have nothing to rest on. A lintel spans the opening and carries the masonry above, transferring the load to the wall on either side. Without a proper lintel, you get the classic diagonal crack rising from the corner of a door or window.
Lintel basics
- Most modern lintels are reinforced concrete, cast in place or precast.
- They should extend into the wall on each side, commonly at least about 150 mm, so they rest securely.
- Depth and reinforcement depend on the span and load. Wide openings need deeper, more heavily reinforced lintels, as designed by the engineer.
- In framed buildings, a continuous lintel band at door-top level often runs around the whole floor, which also helps in earthquakes.
The lintel band and earthquakes
In earthquake-prone regions, a continuous reinforced concrete band at lintel level ties all the walls together, so they act as one box rather than separate panels that can fall outward. Guidance for earthquake-resistant masonry buildings in India recommends such bands.
Chajjas and sunshades
A chajja is a cantilevered projection above a window or door. It throws rainwater clear of the opening and shades the glass from high summer sun. On west and south walls, a deeper chajja, or vertical fins on west windows, keeps rooms noticeably cooler.
Details that prevent leaks
- Give the chajja top a slight slope away from the wall.
- Form a drip groove under the front edge so water drips off instead of running back to the wall.
- Seal the junction between the window frame and the wall.
Leaks around windows are a common cause of damp. See our damp walls guide for diagnosis.
Frequently asked questions
Why is there a crack above my window?
A missing, undersized or poorly bearing lintel, or differential movement between the lintel and masonry. Fine cracks are common; widening cracks need an engineer.
How deep should a chajja be?
It depends on the window height and sun direction. Deeper chajjas give more shade but cost more and need adequate reinforcement as a cantilever.