Stair Step Cracking in Brick: What It Is and When to Worry

Stair step cracking in brick is a crack that follows the mortar joints in a zigzag, usually running diagonally across a wall one joint at a time. If you can trace it up the wall like a staircase, that is what you have. It is a symptom, not a diagnosis, and the right next step is to find out what caused it before anyone fills it.

We repair these walls, and we also tell owners when a wall needs an engineer first. This article explains how to recognize the pattern, what can cause it, and how the repair path works in Chicago. It does not tell you how serious your crack is, because that depends on what is moving and why.

What stair step cracks look like

Look for these:

• A crack that steps up or down along the mortar joints, both the horizontal bed joints and the vertical head joints.
• A crack that starts near a corner, a window or door opening, or the base of the wall and climbs from there.
• A crack that is wider at one end than the other.
• Cracks that show up together with a bulge, a leaning wall or window frames out of square. See bowing brick walls.
• Crack lines that have been patched before and have opened again.
• Rust stains or flaking at the crack, especially over a window or door.

A crack that goes straight through the face of a brick and a crack that follows the mortar joints are different things to a professional. Photograph both so the person who looks can tell them apart.

Why brick cracks in a stair step pattern

Brick and mortar both resist squeezing well and resist pulling apart poorly. When a wall is pushed or pulled unevenly, it tends to open along its weakest line, and in most brick walls that is the mortar joints. That is why the crack steps instead of running straight.

What is pushing or pulling is the question. The things that can be behind a stair step crack include:

• A failing lintel. BIA says steel lintel cracking above openings is commonly tied to excessive deflection, and that unprotected steel needs ongoing maintenance (BIA TN 31B). Cracks that start at the corners of a window or door often come back to this. See rusted lintels and cracking brick.
• Water and salt inside the wall. NPS explains that salt crystallizing inside the masonry can make the face spall or delaminate (NPS Preservation Brief 2). Wet walls move more.
• A mortar harder than the brick. NPS says mortar stronger than the masonry units causes cracking and spalling of the units that cannot easily be repaired (NPS Preservation Brief 2). If someone repointed your wall with hard modern mortar, that can be part of the story.
• Movement at the foundation. A wall that loses support at the bottom cracks above. See foundation wall repair.

We are not saying any of these is the cause of your crack. We are saying a pro has to look, and often open the wall, before anyone knows.

Why you should not patch it

Patching is the most common mistake. Caulk, a smear of cement or a quick repointing over the crack:

• Hides the movement, so nobody can tell whether it is still happening.
• Can trap water behind a hard patch. NPS says moisture and salts leave through the brick if the mortar is less permeable than the brick, and that can damage the face (NPS Preservation Brief 2).
• Gets blamed on the next contractor when the crack reopens.

If you want to know whether the crack is moving, a structural professional will tell you how to monitor it. We would rather you do that than guess.

Who looks at it first

For a stair step crack that is more than a surface blemish, start with an Illinois structural engineer or architect. They find the cause and write the repair. For a plan-based Chicago permit, the City requires plans prepared by an Illinois-licensed architect or engineer, usually an architect or structural engineer (City of Chicago).

If the engineer decides the answer is limited to the masonry, the City's Express masonry permit covers routine masonry maintenance and repair such as tuckpointing, replacing the outer wythe and replacing a lintel up to 6 feet. It does not cover rebuilding all layers of an exterior wall, and a lintel over 6 feet needs drawings by an Illinois architect or structural engineer (City of Chicago). Masonry permits need a City-licensed mason contractor, unless an eligible owner acts as their own contractor (City of Chicago). Confirm the current rules with the Department of Buildings. Our guide to the brick repair permit covers the rest.

How the repair usually goes

The sequence matters more than the technique:

1. Find the cause. Engineer or architect, often with the wall opened up in places.
2. Fix what is causing it. A lintel, a water source, the base of the wall.
3. Repair the masonry. That may be repointing, replacing bricks or rebuilding a section, depending on what the cause turned out to be.
4. Use the right mortar. On older Chicago brick, repointing mortar should be softer and more vapor permeable than the brick and no harder than the original mortar (NPS Preservation Brief 2). BIA likewise says the repointing mortar should be similar to or weaker than the original (BIA Brick Brief). See the mortar mistake that ruins Chicago brick.
5. Watch it. If the crack reopens in the same place, the cause was not fixed.

Water, salt and the white powder

Stair step cracks often travel with other moisture signs: damp patches, rust at lintels and white powder on the face. BIA says efflorescence appearing after the first year usually points to excess water getting in or poor drainage, and is often worst in winter (BIA TN 23A). If you see both cracks and white powder, tell whoever inspects the wall. See efflorescence on brick.

What to ask before you hire

1. Who is determining the cause, and are they an Illinois structural engineer or architect?
2. Will you open the wall to see what is behind the crack?
3. Who pulls the permit, and is the mason City-licensed for brick?
4. What mortar will you use on this brick, and why?
5. How will we know the crack is not moving after the repair?

Start with our self-inspection checklist to see what else is going on with your brick. When you have the cause and a plan, our masonry crew can do the work. The full overview is in the Chicago brick and masonry guide.

Common questions

This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.