Why does a rusting lintel crack the wall?

Steel that corrodes turns into iron oxide, and that rust takes up several times the volume of the metal it came from. The steel sits in a tight pocket of brick with nowhere to expand, so the growing rust lifts the masonry above it. Masons call it rust jacking. It is why the first crack is a clean horizontal line along the joint sitting directly on the steel.

What does the stair-step part of the pattern mean?

The lintel lifts the brick above it in the middle of the opening while the wall beside the opening stays put. That difference has to go somewhere, so the wall shears diagonally through the joints at each end of the lintel. You get a horizontal crack across the opening with short diagonal cracks climbing from both ends, which is close to a signature for the problem.

Can the old lintel just be painted?

Only if you catch it early. Surface rust on a steel angle that has not yet lifted the brick can be wire brushed, primed and painted, and that buys years. Once the wall above has cracked, the steel has already expanded and painting the visible edge does nothing about the corrosion inside the wall. At that point it has to come out.

Do I have to replace the window too?

No. The lintel sits in the masonry above the window frame and can usually be replaced without disturbing the window. We protect the glass and the frame during the work. If the window is being replaced anyway, doing both at once saves a second mobilization and is worth scheduling together.

How long does one opening take?

A standard residential window opening is generally a one to two day job once we are set up, and longer if the bearing pockets have crumbled or the brick above has to be rebuilt. We support the opening, cut, replace and lay back in one sequence rather than leaving a wall propped overnight where we can avoid it.

Why galvanized steel?

Because the failure you are paying to fix is corrosion. Bare mild steel in a damp brick wall starts over again the moment it goes in. Hot dip galvanized angle has a zinc coating that protects the steel for decades, and where the exposure is severe we prime and paint over the galvanizing. A drip or flashing above the lintel matters just as much as the coating.

Lintel Replacement in St. Louis, MO | Gateway Brick & Tuckpointing

Lintel Replacement in St. Louis, MO

Lintel replacement in St. Louis runs $950 to $3,200 per opening. The signal is a straight horizontal crack in the joint a course or two above a window or door, often with short stair-step cracks running up from each end. That is rusting steel swelling behind the brick. We support the opening, cut the old steel out and set new galvanized angle on sound bearing.

Signs you need this

A straight horizontal crack in the joint just above a window or door head

Short diagonal stair-step cracks climbing from each end of that crack

Rust staining bleeding down the brick below the opening

Brick above the window sitting proud of the wall below it

Paint on the exposed steel angle blistering, flaking or gone

A window or door that has started to bind at the top

The crack pattern every brick owner should learn

Stand across the street from your house and look at the heads of the windows. If you see a straight horizontal line in the mortar a course or two above an opening, with short diagonal cracks climbing away from each end of it, you are looking at a rusting steel lintel. The pattern is consistent because the mechanism is consistent. The steel grows, it lifts the brick directly over it, and the wall shears at the points where the lifted section meets the wall that has not moved.

Nothing else on a brick house makes that shape. Settlement gives you diagonal stair-step cracking without the straight horizontal run. Thermal movement gives you vertical cracking at corners and long walls. A bad bearing under a beam gives you crushing rather than lifting. The horizontal crack plus the two diagonals is the lintel.

Why so many St. Louis openings have steel

Older buildings here carried window heads on segmental brick arches or on cut stone. Once steel became cheap, flat steel angles took over, and most of the housing stock from the 1900s onward has a painted angle sitting over every window and door. It is a good detail while the paint holds. The angle is exposed on its outer face, its back sits inside a damp masonry wall, and the only thing between it and corrosion is a coat of paint that nobody has touched since the Carter administration.

Water reaches the steel in two ways. From above, through failed joints or a sill that leaks into the wall. From in front, where the paint has gone and the exposed edge collects every drip running down the face. Both end in the same place. We see the worst of it on north elevations and on walls shaded by a neighboring building, because they stay damp longer.

Supporting the wall before anything is cut

The part of this job you are paying for is the part that happens before the old steel comes out. Brickwork over an opening is carrying load, and on many St. Louis flats it is carrying a second floor. We needle through the wall above the opening or set a shoring frame, take the load off, and only then cut the lintel free. Work done without proper support drops brick, and on a party wall in Soulard it can drop your neighbor’s brick too.

Details that stop it happening again

The new angle is hot dip galvanized and set with full bearing at each end on rebuilt masonry. Where the wall detail allows it, flashing goes in over the lintel with end dams so any water inside the wall is carried out over the steel rather than sitting on it. Weeps go in above the flashing. The brick is laid back in the original bond and pointed with a mix suited to the age of the surrounding wall, which on pre-1930 common brick means lime rather than a portland-heavy mortar. Then we tell you to look at the paint on your other lintels, because they are all the same age.

How the work runs

Confirm the lintel is the cause

Horizontal cracking above an opening has one common cause and a few uncommon ones. We probe the joint, look at the exposed steel edge and check the crack pattern at both ends before committing.

Needle and shore the opening

The brickwork over the opening is supported before anything is cut. Needles through the wall or a shoring frame carries the load so the arch of brick above the window stays where it is.

Cut out the steel and prepare the bearing

The corroded angle comes out along with any crushed brick at each end. The bearing pockets are rebuilt solid, because a new lintel resting on broken brick fails at the ends first.

Set the new steel and lay the brick back

Galvanized angle is set with proper end bearing, flashing goes in above it where the detail allows, and the brick is laid back in the original bond and pointed to match.

What it typically costs

Job	Typical range
Lintel replacement, per opening Opening needled and supported, rusted steel cut out, galvanized lintel set and bricked back	$950 to $3,200
Wide opening or bay front Storefronts, garage openings and bay window heads that need heavier steel and more shoring	$2,800 to $6,500
Clean, prime and repaint sound steel Where the angle has surface rust but has not begun to swell the wall	$180 to $500 per opening
Rebuild a segmental brick arch Where the original head is an arch rather than a steel angle	$1,400 to $4,000
Stone or cast sill replacement Often needed at the same time, since a failed sill feeds water to the lintel below it	$650 to $2,400

Typical ranges for St. Louis and the surrounding area , reviewed September 2026. Every quote is written and fixed before work starts.