Brick cracks above windows when the lintel or arch carrying it moves. The most common cause on older brick houses is a steel lintel rusting: rust takes up more space than the steel it replaces, so it pushes the brick up and cracks the joints at the corners. Sagging steel, a failing brick arch, rotted wood and missing flashing also do it.
When you find cracks above windows in brick, look at the support before the crack. True Course Masonry Newark replaces and repairs lintels and the brick above them across Newark and Essex County, with the work carried out by licensed and insured contractors. This guide explains how openings are spanned, how each type fails, what the cracks look like, and how the repair is chosen. For the service itself, see steel lintel replacement.
What holds up the brick over an opening
A window or door is a hole in the wall, and the brick over it has to be carried across to the brick on either side. Older Newark houses do this in several ways:
- Steel angles. An L-shaped steel section with one leg under the brick and the other standing up behind it, resting on the brick at each side of the opening. It is a common support over openings in brick houses.
- Brick arches. Bricks set on end in a curve, or in a flat “jack” arch with tapered joints, carrying load by compression into the sides of the opening. Many arches also have a steel angle hidden behind them.
- Stone lintels. A single piece of stone spanning the opening, seen on rowhouse fronts and brownstone trim; stone and brownstone repair covers the stone itself.
- Wood lintels. In some older work, timbers carry the inner wythes of a solid wall, or even the face, over an opening.
What the support is cannot always be seen from outside. A thin line of steel at the head of a window, or rust bleeding from the joint just above it, is the usual clue for steel.
How a corroding lintel moves the brick
Steel rusts when it stays wet. Water reaches lintels from the wall above, from open joints and failed sills, and most of all where there is no flashing to carry water off the top of the steel and out of the wall. Rust takes up several times the volume of the steel it consumes, and it forms in layers between the steel and the brick bearing on it. Each layer pushes the brick up a little.
The movement shows up in a recognizable way. Joints crack at the ends of the lintel and step up and away diagonally. The course of brick sitting on the steel may lift or bow. Rust stains run down the face below the lintel. In time, the lintel loses enough thickness to sag in the middle, and the movement reverses: brick over the center drops, and a crack opens across the opening’s head. The ends, where the steel sits in the wall and stays wettest, are often the worst part and the least visible.
Arches, stone and wood
Arches. An arch needs its sides to stay put. If the masonry beside an opening moves outward, or mortar in the arch joints erodes, the keystone or center bricks can slip down. A dropped center brick in a flat arch is a common sign.
Stone lintels. Stone is strong in compression but weak in bending, so a stone lintel that cracks usually cracks near the middle. Steel pins or clamps inside older stonework can rust and split it, too.
Wood lintels. Timber in an older solid wall stays sound while it stays dry. Once a leak keeps it damp, rot lets it compress and the brick above settles. Signs include a sagging head, cracks above both corners and soft, spongy plaster on the interior side of the opening.
Other causes of cracks near openings
Not every crack over a window is a lintel. The Brick Industry Association’s Technical Note 18A explains that on walls with regularly spaced windows, the brick above and below openings moves more than the narrower piers between them, so expansion cracks often start at window corners. Settlement, framing movement and lack of expansion joints can all crack the same spot. The stair-step cracks guide explains how to tell these apart, and a crack pattern alone does not prove a cause.
How urgent is it?
Have it evaluated soon if:
- brick over the opening has dropped, bowed or lifted noticeably
- the lintel is visibly sagging, or rust is flaking off in thick layers
- bricks over a door or walkway are loose
- the window or door has started to stick or bind
- cracks over several openings are widening together
A sagged lintel or displaced brick overhead is a reason to bring in a structural engineer before a scope is set; the engineer or mason guide explains the split. Keep people out from under loose brick and do not tap or pry at it.
Usually plan a repair when:
- rust stains are visible but the brick above is in line
- hairline cracks at the lintel ends have not changed over a season
How lintel repairs are chosen
Clean and coat. Where the steel has only surface rust, keeps its full thickness and has not moved the brick, the exposed steel can be cleaned of loose rust and coated with a rust-inhibiting paint. The joint above the steel is sealed or repointed. This is the lightest repair, and it is only honest where the steel is still sound.
Partial removal and replacement. Where rust has lifted the brick or eaten the steel, the brick above the opening is taken down, often in a stepped pattern, with temporary support as needed. The old lintel comes out, a new galvanized or coated steel angle goes in with proper bearing at each end, and through-wall flashing with an end dam and a drip edge is installed over it. Weeps are left open at the flashing so water can leave. The brick is relaid, reusing original units where possible.
Arch and stone repairs. Dropped arch bricks can be reset, a common task in historic masonry restoration, and cracked stone lintels can be repaired or replaced with matching stone or steel behind a facing, depending on condition and appearance.
Replacement scope depends on the opening’s width, the height of the wall above, how many units can be reused, access and scaffolding, and what turns up once the brick is down. No published range covers lintel replacement here; it is priced from a site visit. Replacement brick matching is covered in the matching mortar and brick guide, and the brick repair cost guide gives ranges for the brick work. Whether a permit is needed depends on the job; the Newark masonry permits guide explains how to check, and taller walls may fall under parapet repair or brick repair.
Before you book a first look
Walk around the house and photograph the head of every window and door, not just the one you noticed. Lintels on the same wall were usually installed together and exposed to the same weather, so one rusting lintel often means others are close behind. Note which openings have rust stains, which have cracks and which have moved, then send the set through the contact page.