A steel lintel is a horizontal steel member, usually an L-shaped angle, that spans the top of a window, door or other opening in a masonry wall and carries the brick, block or stone above it to the wall on each side. Without it, the masonry over the opening would sag onto the window frame or fall out. In an Ontario brick house there is one over almost every window and door, even though you rarely see more than a thin dark line of steel under the bottom course of brick.
This post explains what a lintel does and how it works. For when the code requires one, see when is a steel lintel required; for the different shapes, see types of steel lintels.
What a steel lintel does
A lintel has three jobs, and only the first is obvious.
- It carries the masonry over the opening. Brick and stone are strong in compression but can't span a gap on their own. The lintel picks up the masonry above the opening and delivers it to the solid wall at each side, so the window or door frame below carries nothing.
- It keeps the wall true. The bottom course of brick over the opening sits on the lintel's horizontal leg. A stiff lintel keeps that course straight and level, which keeps mortar joints from cracking.
- It anchors the water management at the head of the opening. In a brick-veneer or cavity wall, water that gets behind the brick runs down the cavity. Flashing laid over the lintel turns that water out through weep holes above the window. The lintel is the base of that detail.
"Steel lintel meaning" in one line: it's the beam over an opening in a masonry wall. "Lintel" is the general word for that member in any material; in Ontario housing, the masonry ones are almost always steel.
How a steel lintel carries the load
You might expect a lintel to carry all the brick from the window up to the roof. It doesn't, because brickwork arches.
Once the mortar has set, the bricks above an opening lock together and push sideways into the wall at each side, like a flat arch. The masonry outside a triangle over the opening carries itself into the jambs. The lintel only has to hold up the bricks inside that triangle. The design notes behind the 2024 Ontario Building Code's veneer lintel table assume exactly this: brick weight within a 45 degree angle from each edge of the opening is not counted in sizing the lintel.
That's also why the code's table for lintels in solid masonry walls (Table 9.20.5.2.-A) tells you to leave out the floor load when the distance from the lintel to the bottom of the floor framing is greater than the width of the opening. A floor that sits high enough above the opening is carried by the arching masonry, not by the steel.
Arching only works when there's enough solid wall around it. It can break down when:
- the masonry above the opening is short, such as a window just under the eaves or a floor;
- another opening sits close beside or above, cutting into the arch;
- a post, girder truss or beam end lands on the wall over the opening;
- the wall has been altered, cracked or poorly built.
In those cases the lintel may carry far more than its table assumes, and it needs to be designed for the real load. This is one reason enlarging or adding an opening in an existing wall is a job for a designer or engineer and usually needs a permit.
Where you'll find steel lintels in a house
The kind of wall decides what kind of lintel you have:
| Wall | What the lintel looks like |
|---|---|
| Brick or stone veneer over wood framing | A single steel angle in the brick, with a separate wood header in the frame behind it |
| Concrete block wall | Two angles back to back, or a pair of angles with a plate, under both faces of the block |
| Solid (double) brick, common in older Ontario houses | An exterior angle plus interior angles carrying the inner wythes and often a floor |
| Wide opening in a brick house (garage door, patio wall) | A W-beam or tube with a plate welded on to carry the brick, on steel posts |
Note the first row. In a brick-veneer house, two members span each opening: the steel angle carries the brick, and a wood lintel (header) in the stud wall behind carries the floor and roof. That catches out many renovators. The difference is explained in steel lintel vs beam. If you want to know what's in your own wall, our post on is my lintel steel or concrete covers how to tell.
What a steel lintel needs to work
A lintel is a simple piece of steel, but it only performs if four things are right:
- Size. For ordinary openings, the 2024 OBC sizes the angle from its tables by span and wall type. The tables for loose lintels are based on a mid-span deflection limit of span/700, which is much stiffer than a floor beam, because brick cracks if the steel under it sags. Openings outside the tables are designed.
- Bearing. Lintels sized from the code tables need at least 150 mm of even, level bearing at each end, on masonry, concrete or steel (Sentence 9.20.5.2.(3.1)). Short bearing crushes the brick at the jamb. See steel lintel bearing length.
- Corrosion protection. Steel angle lintels supporting masonry must be prime painted or otherwise protected from corrosion (Sentence 9.20.5.2.(4)). Exterior lintels are often hot-dip galvanized.
- Flashing and weeps. Water has to be shed off the lintel, not left sitting on it. Flashing over the lintel, end dams and open weep holes do that job.
When those go wrong, the usual failure is rust. Steel expands as it corrodes, lifting the brick above it and cracking the mortar. The signs and the fix are covered in replacing a rusted steel lintel.
Lintel, header, beam: sorting the words
These terms overlap on site, so it helps to pin them down:
- Lintel: the member over an opening in a wall, steel or concrete in masonry.
- Header: in wood framing, the wood lintel over a window or door. In some trades, any member over an opening.
- Beam: a horizontal member carrying floors, roofs or walls between supports, not tied to an opening. A wide opening can need a beam acting as a lintel.
- Sill: the member at the bottom of the opening, not the top.
Getting a steel lintel made
We supply angle lintels for masonry openings, cut to length and punched or welded as needed, and fabricate beam and tube lintels with welded plates to your drawings. We can prime or galvanize to suit, our welding is CWB certified, and we deliver across the GTA and Ontario. If you're replacing a lintel or cutting a new opening, have the size confirmed by your designer, then send us the span, wall type and finish.
Request a quote for your lintel, or see our steel products.
Frequently asked questions
What is a steel lintel?
A steel lintel is a horizontal steel member, usually an angle, that spans the top of a window, door or other opening in a masonry wall and carries the brick, block or stone above it to the wall on either side.
What does a steel lintel do?
It carries the masonry over the opening so the window or door frame takes no load, keeps the bottom course of brick straight and level, and gives the flashing above the opening something to sit on so water in the wall drains out.
How does a steel lintel work?
It acts as a short beam. Thanks to arching in the brickwork, it usually carries only a triangle of masonry above the opening rather than the whole wall, and it passes that load into the masonry at each end through its bearing.
Does every window have a steel lintel?
Every opening with masonry above it needs a lintel or an arch. In a brick-veneer house that is normally a steel angle over each window and door. Walls with siding over wood framing use wood headers instead, and concrete walls use reinforced concrete.
