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

September 4, 2026

The most common masonry call in Kettering, Huber Heights, Beavercreek, and Centerville sounds like this: there is a crack over the living room window that follows the mortar joints up in a staircase, somebody repointed it two years ago, and it is back. It is back because it was never a mortar problem. On a brick house built after about 1950, a stair-step crack that starts at the top corner of an opening is a rusted steel lintel until proven otherwise, and no amount of new mortar will hold a joint that a swelling piece of steel is pushing apart from below.

Here is how to read the crack, what each cause costs, and why the order of repairs matters.

Three cracks that look alike

The lintel crack. Starts at the top corner of a window or door, steps up and outward along the joints, and often opens a horizontal gap right along the top of the lintel. The brick directly above the opening may bow outward. Rust streaks stain the brick under the lintel, and if you look up at the steel from below you can see it flaking or bellied. Worst on the north and west faces of the house, which stay wet longest, and the crack tends to open a little wider in a wet April and close slightly in a dry August as the rust swells and shrinks.

The settlement crack. Starts low, at a lower window corner or at the foundation, and runs diagonally toward a corner of the house. It shows up at more than one opening on the same side, and often inside as diagonal plaster cracks or doors that stick. The cause is the ground: the Miamian series soil that dominates Montgomery, Greene, and Clark counties is 35 to 45 percent clay in its subsoil with a perched water table 2.5 to 3.5 feet down from January through May, and a footing riding that clay rises in a wet spring and drops in a dry fall.

The mortar crack. Joints eroded or washed out along a run, with no displacement of the brick, usually under a leaking gutter or at a weather corner, and not tied to an opening at all. Ohio’s roughly 110 freeze-thaw cycles a year do this to any joint that holds water. This one really is a repointing job.

The distinction matters because the fixes cost different money and the wrong one buys a season.

Why lintels rust in Dayton

Every opening in a brick veneer wall has a steel angle, the lintel, carrying the brick above it. The brick on a postwar house in the Dayton suburbs is a veneer over a wood frame, and the lintels of the 1950s through the 1970s were routinely installed bare: no primer, no flashing over the steel, no weep holes in the joints above it. Kettering became a city in 1955 and added more than 30,000 residents through the 1970s; Charles Huber started his first plat of brick ranches in 1956 and Huber Homes built 10,707 houses by 1992; Beavercreek’s subdivisions filled in around the former villages and incorporated in 1980. Tens of thousands of lintels went in the same way in the same years.

Water always gets behind brick veneer. Dayton supplies 41.33 inches of normal annual precipitation, spread through the year, and 25 inches of snow. That water runs down the cavity, reaches the lintel, and sits on the horizontal leg of the angle with nowhere to drain. Steel rusts. Rust occupies several times the volume of the steel it consumes, so the lintel grows thicker. The brick sitting on it has nowhere to go but up, and the joints above the corners of the opening, where the lift is concentrated, open in a staircase. Then Dayton’s winter, with its January normal high of 37.1 and low of 21.8, freezes the water in the new crack roughly a hundred times and widens it.

A repointed lintel crack fails because the steel is still rusting under it. By the following spring the new mortar has cracked along the same line.

What each fix costs

Several lintels on the same elevation cost less per opening than one, because the setup is shared. The pricing page has the full table.

How a lintel replacement actually goes

1. Shore the wall above the opening and remove the brick above the lintel course by course, saving sound units.
2. Pull the rusted steel and inspect the sheathing and wrap behind it, which has been holding water for years.
3. Set a new lintel in galvanized or primed steel sized for the span, bearing at least several inches onto sound brick at each end, on a mortar bed.
4. Flash and weep. Flashing is lapped over the lintel and turned up behind the veneer so water that reaches the steel drains out; weep holes are left in the head joints above it. This is the step the original builders skipped and the reason the new lintel will outlast the old one.
5. Relay the brick in matched mortar, toothed into the existing courses, with salvage replacements for any cracked units. See brick repair.
6. Repoint the crack line. Now that the cause is gone, the step crack gets cut out to depth and repointed, in Type N on a postwar house.

The lintel and sill page has the same sequence with the details on sills, which usually get done at the same window since the scaffold is already up.

Old houses have stone lintels, and different cracks

On Dayton’s 19th-century brick in the Oregon District, St. Anne’s Hill, South Park, and Dayton View, the opening is carried by a stone lintel, a brick jack arch, or a segmental arch, not steel. A stone lintel cracked at midspan has usually been overloaded or is bearing on a corner that settled, and the repair is a stone repair: pinning and patching, or replacement in matching limestone. A jack arch that has dropped a wedge of brick in the middle is a bearing problem at its ends. And on these houses the diagonal settlement crack is far more common than on postwar veneer, because the foundations are rubble stone in lime mortar on the same clay. The stone page and the foundation page cover those.

When it is settlement

If the crack starts low and runs toward a corner, if it shows at more than one opening on the same side, or if the basement wall below it has a step crack of its own, the ground is moving. Preservation Brief 2 makes the general point for every masonry repair: fix the cause first, whether a leaking gutter, a downspout dumping at the footing, or differential settlement, or the repointing is wasted. In practice, most Dayton settlement cracks trace to water at one corner: a downspout with no extension, a grade that slopes toward the house, a window well that fills. Extending the downspout and regrading is cheap, and the crack line gets repointed only after a season shows the movement has stopped. A wall that keeps moving after drainage is fixed is a foundation conversation, and we will say so rather than repoint it a third time.

What to photograph

A straight-on shot of the whole window so the crack pattern is visible, a close-up of the crack with a coin for scale, a photo looking up at the underside of the lintel from below, and one of the foundation wall in the basement directly under that window. From those four pictures we can usually say lintel, settlement, or mortar, and quote it against the published ranges. If it is the lintel, replacing it is a one-day job per opening in the mortar season, mid-April through October between Dayton’s average freeze dates of April 16 and October 25, and it is the last time that crack gets fixed. Process questions are on the FAQ.