What is it?
A lintel is the horizontal structural member that spans across the top of a door or window opening, carrying the wall above across the gap and transferring that load down to the masonry either side.
Without a lintel, the wall above an opening would have nothing to span on and would simply fail into the gap.
- 1Blockwork (external leaf)
- 2Insulated Lintel
- 3Cavity Closer
- 4Blockwork (internal leaf)
What does it do?
The lintel picks up the weight of everything bearing on it from above (masonry, floors, roof loads, depending on where in the building the opening sits) and carries it as a beam across the opening, delivering it down into the jambs (the masonry either side) rather than the opening itself.
In a cavity wall, both leaves usually need their own lintel, since each leaf is a separate structural skin: an outer lintel to carry the brickwork above, and an inner lintel to carry the blockwork, although these can be combined into a single product.
Where is it used?
Over every structural opening in a loadbearing wall: doors, windows, and any other gap that interrupts the masonry.
Types
Domestic lintels over openings like doors are most commonly pressed steel cavity lintels, a galvanised steel section profiled to support both leaves of a cavity wall and often incorporating a built-in cavity tray to direct water that gets into the cavity back out at the opening. Longer spans or heavier loads may use precast concrete or steel beam lintels instead.
How to specify
Lintel size and type are set by the span of the opening and the load coming down onto it. Wider openings and heavier loads above need deeper, stronger lintels, and this is a Structural Engineer's calculation, not a standard size picked by eye. Manufacturers publish load-span tables for their standard cavity lintel ranges, which cover most domestic situations directly.
Other considerations
A lintel needs enough bearing at each end (the length it actually rests on the masonry either side) to safely transfer its load down; too little bearing is a common site error. Where a lintel incorporates a cavity tray, that tray needs weep vents at the ends to let any water it collects escape.
Interacting elements
- Facing brick / Blockwork: the lintel bears onto and supports the masonry above the opening
- Cavity insulation: the lintel's cavity tray interrupts the cavity, so insulation continuity is detailed around it. Many pressed steel lintels designed specifically for cavity walls will include rigid insulation to fill the profile.
- Weep vents: drain water collected by the lintel's cavity tray back out of the wall