Step Cracks Over the Window: When It Is the Lintel, Not the Mortar

September 4, 2026

The most expensive mistake an Evansville homeowner makes with brick is paying to repoint a stair-step crack over a window. It looks like a mortar problem. It is a diagonal line of open joints climbing away from the corner of the opening, and every joint in it is missing mortar, so the natural call is a mason to fill them. The mason fills them, the wall looks fine for a season, and the next spring the same crack is back, a little wider. That crack is not a mortar failure. It is the wall telling you that the steel angle carrying the brick above the window has rusted and is lifting the courses above it, and no amount of mortar will hold it down. This post is about reading the crack, understanding why Evansville’s climate makes it so common, and what the actual fix costs.

How a brick opening carries its load

Brick cannot span a window on its own, so every opening has something carrying the courses above it. On Evansville’s oldest houses, in the Riverside Historic District, Washington Avenue, Bayard Park, Culver, and Lamasco, that was usually a brick jack arch or segmental arch, or a cut Indiana limestone lintel. From the 1920s on, and universally by the post-war years, it was a steel angle iron, an L-shaped section resting on the brick at each side of the opening with the outer wythe of brick sitting on its horizontal leg. Lincolnshire’s Tudor and Colonial Revival houses, platted after 1923, are full of them. So are the 1920s to 1950s East Side and every brick ranch in Newburgh’s 1960s and 1970s subdivisions.

Those angles were often bare or painted once at installation. Galvanizing became common later and was inconsistent even then. A lintel installed in 1930 has now spent nearly a century with water running down the brick face onto its top surface.

Why rust cracks brick

Steel rusts, and rust takes up several times the volume of the steel it came from. As the angle’s horizontal leg swells, it lifts the course of brick sitting on it. The brick above is bonded into the wall on either side of the opening, so the lift has to be relieved somewhere, and it relieves itself along the weakest line: the mortar joints, in a diagonal stair-step running up and away from the top corner of the window. Masons call it rust jacking. The crack is not the problem. It is the symptom of a force that is still there.

Evansville’s weather feeds it from both ends. NOAA’s 1991-2020 normals for Evansville Regional Airport count 92.6 nights a year at or below 32 degrees against only 15.5 days that stay frozen, so roughly 77 times a winter water in the crack over the lintel freezes, expands, and pries the joints wider, then thaws and runs down onto the steel. The same normals put annual precipitation at 45.31 inches, with the wettest months in March at 4.60 inches, April at 5.14, and May at 5.12, right when the last freezes of the season (11.9 freezing nights in March, 2.3 in April) are still happening. Wet steel, freezing water, and a crack that lets in more of both: the cycle is self-reinforcing, and it is why a rust line noticed ten years ago is a stair-step crack today.

Reading the crack

Here is how a mason tells the two apart from the sidewalk:

It is the lintel when:

• The crack starts at the top corner of a window or door and climbs diagonally in stair-steps, following the joints.
• There is a horizontal crack, or an open bed joint, running along the course directly over the opening.
• The brick over the opening stands proud of the wall, or the soldier course (the vertical bricks over the window) has sagged and opened at the head joints.
• There is a rust stain on the brick under the top of the opening, or you can see a flaking rust line where the steel meets the brick.
• The limestone sill under the same window has cracked, usually near the middle or at a jamb, because it is now carrying an uneven load.
• The window binds or a door no longer latches.

It is the mortar when:

• Joint loss is scattered across the wall and follows the weather: the chimney, the parapet, the north face, the joints under sills.
• The joints are recessed or crumbling but the brick courses are still straight and level.
• There is no relationship between the failed joints and the openings.

It is movement, and neither trade alone, when:

• A vertical crack runs through brick and joints alike at a corner or near mid-wall.
• One side of the house has dropped and the cracks widen toward it.
• A long horizontal crack runs at mid-height on a basement wall. That is soil pressure, and the foundation page explains why mortar is not the answer.

What repointing a lintel crack actually buys you

One season. The joints get filled, the wall looks finished, and the steel underneath keeps swelling. By the following spring the new mortar has cracked along the same line, because a filled joint has no strength against a lifting force. The homeowner has now paid for a repair that had to be cut out again to do the real one. On a house with four rusted lintels across the front, that mistake gets made four times.

What the real fix looks like

The lintel and sill page has the full process; the short version:

1. Shore the brick above the opening with needles or a temporary support.
2. Cut out the lintel course. The joints are cut, the brick over the angle is removed and saved, and the rusted steel comes out. The cavity and any weeps are checked while the wall is open.
3. Set a new galvanized or stainless angle, sized to the span, with at least 4 to 6 inches of bearing at each side, on a mortar bed, with flashing and weep holes above it where the wall has a cavity so the next ninety years of water has somewhere to go.
4. Reset the saved brick in mortar matched to the wall: lime-based on pre-1930 brick, Type N on 1920s to 1950s, Type S on modern.
5. Repoint the stair-step, now closed, ground to depth and packed in lifts like any tuckpointing job.
6. Fix the sill at the same visit if it cracked, pinned and patched or replaced with new cut limestone; see the stone page.

On the oldest houses, where the lintel is a brick arch or a stone, the repair is different: the arch is re-supported and repointed with spalled voussoirs replaced from salvage, and a cracked stone lintel is pinned or replaced with new Salem Limestone cut to the original section.

What it costs

Steel lintel replacement runs $400 to $900 for a standard ground-floor window and $900 to $1,500 for a wide or upper-floor opening; brick arch repair runs $600 to $2,000; sill repair or replacement $300 to $1,200. Most crews carry a $500 to $800 minimum, so a house with several rusted lintels should have them done in one visit, one scaffold setup, one mortar match. The full table is on the pricing page. A lintel is structural, so a permit is often required, and in Evansville the work should be done by a crew holding the Building Commission’s brick and masonry contractor license, which requires a $25,000 bond and $300,000 in liability insurance. In the Riverside Preservation Area, in-kind lintel work that puts the brick back to match is generally ordinary maintenance under city code, but a street-facing opening is worth a call to the Historic Preservation Officer first.

When to do it

Before winter. NWS Paducah puts Evansville’s average first fall freeze at October 29 and the average last spring freeze at April 6, and mortar cannot be placed with the wall below 40 degrees and falling. A stair-step crack noticed in September should be scheduled now, so the steel comes out before 77 freeze-thaw cycles work on the crack. A crack noticed in January can wait for April, with the joints temporarily sealed against water if they are wide. What it should never get is a repoint-only quote. If a bidder looks at a diagonal crack off a window corner and quotes tuckpointing without mentioning the lintel, get another bidder.

Send a straight-on photo of the whole opening, a close-up of the crack with a coin for scale, and a shot of the sill, and you will get the lintel-or-mortar answer and the number, usually the same day.