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Lintels: What Holds the Brick Up Over Your Windows

Every window and door in a brick wall has something spanning the gap above it. On most homes in Rutherford County that something is a piece of steel, and steel in a wet wall does not sit still.

Brick cannot span an opening by itself

Brick is strong in compression and weak in bending. Stack it and it will hold enormous weight. Ask it to bridge a four foot gap over a window and it has nothing to hold it there.

So every opening needs a spanning element. On homes built in Middle Tennessee over the last several decades, that element is almost always a steel angle, commonly called a lintel or a shelf angle. The brick above the window sits on the horizontal leg of that angle, and the angle carries the load sideways into the brick on either side of the opening.

Older buildings solved the same problem differently, with brick arches, stone lintels or heavy timber. The physics did not change. Only the material did.

How a steel lintel actually works

Picture an L shaped piece of steel running the width of the opening. The vertical leg hides in the wall behind the brick face. The horizontal leg projects out under the first course above the window, and that course and everything above it rest on it.

The load then travels to the ends. This is why bearing length matters. A lintel needs to sit a meaningful distance onto solid masonry at each end, and one cut too short concentrates that weight on a small patch of brick at the jambs.

The other detail is what happens above the lintel. Water inside a masonry wall runs down and needs a way out. That means flashing over the lintel and open weep holes in the course directly above it, so the drainage path does not dead end on a piece of steel.

• Steel angle spanning the opening, hidden behind the brick face
• Adequate bearing onto sound masonry at each end
• Flashing above it to carry water back out of the wall
• Open weep holes in the joint directly over the opening
• A joint under the ends of long angles so the steel can move without cracking brick

Rust jacking, the failure that defines this subject

Steel corrodes when it stays wet. What makes it a masonry problem rather than a cosmetic one is volume. Rust occupies several times the space of the steel it consumed, and it forms in layers between the lintel and the brick sitting on it.

That expansion has nowhere to go but up. It lifts the brick course above the opening, opens the bed joint into a visible horizontal line, and pushes the wall outward. Masons call it rust jacking, and it is why a small maintenance issue turns into a structural repair if it runs long enough.

Our climate feeds it. Wind driven rain from spring storms pushes water into the wall, freeze thaw cycling works joints open and gives it more entry points, and humid summers keep the cavity from drying quickly. Steel in a wall here has plenty of opportunity to rust.

The warning signs above an opening

Rust jacking announces itself well before anything falls. The signs are subtle at first and they cluster directly above windows and doors, which is what distinguishes them from general settlement cracking.

Stand back and sight along the wall above each opening. A course that is no longer level, or brick that bows outward compared to the wall on either side, is the classic pattern. Then get closer and look at the joints and the visible edge of the steel.

• A horizontal crack in the mortar joint just above a window or door
• The brick course above the opening lifted or bowed out of plane
• Orange or brown staining bleeding down the brick from that joint
• Paint blistering or flaking off the exposed edge of the lintel
• Windows or doors that suddenly bind, particularly garage doors
• Cracked or crushed brick at the corners of the opening

Why it turns up so often on homes here

Three habits account for most of the lintel failures found around Rutherford County, and none of them are exotic.

The first is a drainage path that never worked. If flashing above the lintel was skipped or the weep holes were mortared shut, water sits on the steel instead of leaving the wall. The second is paint used as maintenance. A coat of paint on the visible lintel edge looks like protection, but water is reaching the steel from behind, and paint on the front does nothing about that.

The third is age plus neglect. A lot of the brick housing stock here, including much of the older rental property near MTSU, has lintels that have never been touched since construction. Steel does not need attention often. It does need it eventually.

What a lintel repair involves

This is not a caulk and paint job once jacking has started, because the expanding rust sits under the brick and has to be removed.

The sequence is fairly consistent. The brick above the opening is shored or temporarily supported, the affected courses are carefully taken down and salvaged where possible, the steel is exposed, and then it is either cleaned back to sound metal and coated or replaced outright if section has been lost. Flashing and weeps get installed or corrected, and the brick goes back with mortar matched to the existing wall.

Cost tracks the width of the opening, the courses above it, whether the brick can be reused, and access. A single window on a one story ranch is a modest job. A row of openings on a two story elevation needing scaffold is a different scale, and only a site visit produces the real number.

• Temporary support for the masonry above
• Careful removal and salvage of the affected courses
• Steel cleaned and coated, or replaced where section is lost
• Flashing and weep holes installed or restored
• Brick relaid with matched mortar and a matched joint profile

Arches, stone and what to check on new construction

Not every opening uses steel. Jack arches and segmental arches carry load through the geometry of the brick itself, wedging the units against each other so the load travels to the jambs. You see both on the older buildings around the Murfreesboro square, and when they fail it is usually because the abutment beside them moved, not because the arch was weak.

Precast concrete and cut stone lintels also appear, especially on newer builds going for a particular look. They do not rust, which removes one failure mode, though they still need the flashing and drainage above them.

On a new build in Smyrna or La Vergne, the useful moment to look is before the brick goes up past the openings. Ask to see flashing over the lintels and confirm the weep holes above them stay open. It takes five minutes and it is the cheapest lintel maintenance you will ever do.

Related services: Chimney Masonry Repair