The quickest way to tell is to stand outside and look up at the underside of the brick over a window or door. If you see a thin, flat strip of metal tucked under the bottom row of brick, often painted or rust-stained, it's a steel lintel, and a magnet will stick to it. If instead there's a solid band of grey or stone-coloured concrete on the face of the wall, as tall as a course or more of brick, it's a concrete lintel. In most brick veneer houses in Ontario, the answer is steel.
This post walks through what each type looks like, the simple checks that confirm it, the cases that fool people, and why it matters when you're dealing with cracks, rust or a replacement.
What a steel lintel looks like
Most steel lintels in houses are angles: an L-shaped piece of steel with one leg standing up behind the brick and the other leg lying flat under it. Once the wall is built, most of the angle is hidden.
What you can see:
- From below: a flat steel strip running the full width of the opening and a bit beyond, about as wide as the brick it carries. In the 2024 Ontario Building Code's table for angle lintels supporting masonry veneer (Table 9.20.5.2.-B), the horizontal legs range from 76 mm to 102 mm, roughly the width of a brick.
- From the front: just a thin edge, the thickness of the steel. The angles in that same table range from 6.4 mm to 13 mm thick, so you're looking at a line, not a band.
- Colour and finish: usually painted black, brown or a colour matched to the trim, sometimes galvanized grey, and often streaked with rust where the paint has worn.
- Flashing: a strip of flashing or membrane may show at the joint just above or below the lintel.
On solid masonry walls, such as older double-brick houses, there may be two or more angles side by side under the full wall thickness, sometimes bolted together. The interior ones are hidden behind plaster.
What a concrete lintel looks like
Concrete lintels are reinforced concrete beams, either precast and set in place or cast with the wall. They show on the face of the wall:
- A solid band of concrete over the opening, typically as tall as one or more courses of brick or block.
- Bearing on each side of the opening, so the band runs past the edges of the window or door.
- A plain grey or tinted finish, sometimes made to look like stone.
- No metal visible from below, just concrete on the underside.
In concrete block walls (basements, garages, commercial buildings), you may also see block lintels: special U-shaped lintel blocks laid over the opening and filled with grout and rebar. From outside they look like a regular course of block, sometimes a little different in texture. The reinforcement is inside, out of sight.
Quick checks to confirm
| Check | Steel lintel | Concrete lintel |
|---|---|---|
| Look at the underside of the opening | Thin flat metal strip | Concrete surface |
| Look at the face of the wall | Only a thin edge, or nothing | A visible band, a course or more tall |
| Magnet on the underside | Sticks | Doesn't stick (unless it finds a buried bar or nail) |
| Tap with a screwdriver handle | Sharp metallic ring | Dull knock |
| Common signs of age | Rust streaks, flaking paint, cracks in brick above | Cracks, spalled corners, rust stains from bars inside |
The magnet test is the most reliable. Use a strong fridge or pick-up magnet on the flat underside, not on the brick.
Cases that fool people
- Decorative precast or stone "lintels." Many houses have a cast stone band or keystone over windows. It looks like a concrete lintel, but there's often a steel angle under or behind it doing the structural work. Check underneath with a magnet.
- Soldier courses. A row of bricks standing on end over a window looks like a structural feature, but in veneer walls it usually sits on a steel angle.
- Brick arches. True masonry arches carry themselves and may have no lintel at all, though many arch-shaped openings in newer veneer have a bent steel angle or a flat angle behind.
- Painted steel that looks like concrete. Thick paint or trim coverings can hide the steel. Again, the magnet settles it.
- Inside the house. Behind the brick veneer of a typical frame house, the wood-frame wall has its own header, usually wood. That header is separate from the steel angle carrying the brick.
- Poured concrete foundation walls. An opening in a poured wall, such as a basement window, usually has no separate lintel. The wall above spans the opening, and any reinforcement is cast inside it.
Why it matters
Knowing the type tells you what you're dealing with when something goes wrong:
- Steel lintels rust. When the steel corrodes, the rust takes up more room than the steel did and can lift the brick above, causing stepped cracks from the corners of the opening, a sagging line of brick or displaced mortar. Our post on whether steel lintels rust explains why it happens and how coatings help.
- Concrete lintels crack and spall. Cracks across the lintel, broken corners or rust stains coming from inside suggest the reinforcement is corroding or the lintel is overloaded.
- Repairs differ. A rusted steel angle can be cleaned and painted while it's still sound, or replaced by removing the brick above, shoring and installing a new angle. Our guide to replacing a rusted steel lintel walks through the process. Concrete lintels are usually repaired with concrete patching methods or replaced as a unit.
- Widening an opening. If you're making a window or door wider, the existing lintel almost never works for the new span. The new lintel is sized from the OBC tables or by a designer; see steel lintel sizes under the Ontario Building Code.
For a fuller comparison of the two materials, see steel lintel vs concrete lintel.
When to get a closer look
Have a mason, contractor or engineer look at a lintel if you see:
- Stepped or vertical cracks running up from the corners of a window or door.
- Brick above an opening that has dropped, bulged or separated from the frame.
- Heavy rust with flaking layers on a steel lintel.
- Cracks across a concrete lintel or chunks breaking off.
Structural work on lintels, including replacing one or widening an opening, usually needs a building permit, and the replacement lintel has to be sized for the span and the wall it carries.
Steel lintels cut to your opening
We cut, drill and fabricate steel angle lintels and steel beams for wider openings, and we can prime or galvanize them to suit, with delivery across the GTA and Ontario. Send us your opening sizes or drawings for a quote, or see the lintels and beams we fabricate.
Frequently asked questions
How do I know if I have a steel lintel?
Look up at the underside of the brick directly above a window or door from outside. A steel angle lintel shows as a thin, flat strip of metal, often painted or rust-stained, running the width of the opening and tucked under the bottom course of brick. A magnet will stick to it.
What does a steel lintel look like?
From the front you usually see almost nothing, because the vertical leg of the angle is hidden behind the brick. From below you see a flat metal strip about as wide as the brick, with a thin edge at the front. It may be painted, galvanized grey or rust-coloured.
What does a concrete lintel look like?
A precast or cast-in-place concrete lintel shows on the face of the wall as a solid band of grey or stone-coloured concrete over the opening, usually as tall as one or more courses of brick or block, extending past each side of the opening.
Are most lintels in Ontario houses steel?
In brick veneer houses, the brick over windows and doors is almost always carried on a steel angle lintel, with a wood header behind it carrying the framed wall. Decorative stone or precast bands over windows often hide a steel angle behind or under them.
