Vertical Foundation Cracks: Common, Varied and Worth Recording

Vertical cracks in a foundation wall, defined

A vertical foundation crack is a line that runs from top to bottom, or part way, in a plumb direction. It may be straight or slightly wavy. It may be thin or wide, dry or damp. Unlike a level crack, which often hints at sideways pressure, a vertical crack can come from several different processes.

HUD’s foundation guide puts the causes in a single sentence.

Basement wall and floor cracks can be caused by a variety of factors, including drying shrinkage, thermal contraction, restraint to shortening, subgrade settlement, and applied loads, including those due to expansive soils, hydrostatic pressure from high water tables, and in some parts of the country, seismic activity ¹.

That range is why this page does not diagnose. It describes the pattern, the usual contributors and the facts that help an engineer read it. The live guide on foundation cracks compares all patterns.

Vertical cracks: pattern, possible contributing factors and what to record

How a vertical crack can form

Two common routes are shown. They are simplified, and real walls can combine them.

1. Drying route: block or concrete shortens as it dries, the wall is held at its ends or base, and tension builds until a crack opens ¹².
2. Temperature route: a wall contracts as it cools, and a joining wall does not follow, so a vertical crack opens where they meet ².
3. Settlement route: part of the footing loses support, so one part of the wall drops against its neighbor, and a nearly vertical crack opens with edges that do not line up ².
4. Water route: water pressure or frozen soil acts on the wall and adds to cracking ¹.
5. Result: a crack that looks the same from the room can have come from different causes.

Example: two vertical cracks, two readings

The two-crack example below is an illustration of how details change the reading. The walls are invented. The mechanisms come from HUD’s guides ²¹.

Crack B is not “worse” by shape. It simply has more details that call for an engineer’s look. Neither can be judged from a photograph.

Where vertical cracks show up

Vertical cracks show up in poured basement walls, block walls and stem walls, and in the above-ground masonry that sits on them. HUD’s guide places vertical cracks near wall ends and at short offsets among thermal-movement cracks in above-ground masonry ².

They also appear near door and window corners inside the house, where drywall tapes crack. Those are cosmetic when they come from small movement, but a new, sharp crack may indicate movement behind the wall that should be investigated ².

In slab-on-grade houses, floor cracks follow different patterns. See cracks in slab foundations.

Why naming the pattern helps

What this pattern does not tell you

• A vertical crack does not show whether it is active. Only repeat readings do. See foundation movement monitoring.
• It does not separate drying shrinkage from settlement by looks alone. HUD says many masonry cracks blamed on settlement come from moisture or thermal movement ².
• It does not give a safe width. No width is given here, and none should be trusted from a blog.
• It does not prove water will come in, or that it will not.

What drives the cost of dealing with a vertical crack

We print no prices. If a crack is stable and dry, the work may be small: sealing as a professional directs and water control. If it is leaking, drainage or waterproofing questions enter. If it marks settlement, the cost depends on the soil and an engineer’s design.

Drivers include whether the crack is active, whether water comes through, the wall material and height, access, and how many cracks there are. Investigation adds a cost before any repair is chosen.

See the cost guide and the cost calculator for factors tied to your inputs.

What to do if you find one

1. Photograph it with a ruler or coin, and note the date and spot ¹.
2. Check the edges. Do both sides sit flush? Write down what you see.
3. Check for water. Look for damp, staining or white mineral deposits after rain.
4. Monitor it. Photograph from the same spot each month, or add a crack gauge.
5. Describe it with the crack identification tool.
6. Ask a licensed structural engineer if the crack changes, leaks, shows an offset, or comes with sticking doors.

Habits that protect the wall

• Keep gutters clear and downspouts discharging well away from the wall.
• Keep surface soil sloping away from the foundation. See grading around a foundation.
• Keep a dated log of every crack and of any dampness or leaks.
• Do not stack heavy material against the wall.
• Keep irrigation heads from soaking the soil next to the foundation.

Risks of ignoring a vertical crack

The first risk is that a crack tied to settlement keeps growing. HUD says large differential settlements are more serious, because they cause movement in joists, floors and roofs that must be evaluated ². The second risk is water entry, which can damage finishes and add to the problem.

The third is the opposite: panic. HUD’s foundation guide says settlement usually happens over time and is not a dramatic event, which leaves time to research the cause ¹. Calm, recorded observation and a professional’s look beat both ignoring and rushing.

Never assume a specific crack is harmless, and never assume every crack needs underpinning.

Codes, standards and crack control

Model building codes do not prescribe crack-control steel or control joints for low-rise masonry in most regions, according to a HUD study of concrete masonry homes. The same study says the masonry industry makes crack-control recommendations, and that cracking can occur from temperature and moisture change or differential settlement of foundation soils ³.

In other words, a vertical crack does not by itself prove a code violation. Whether a wall met the code in force when it was built is a question for the local building department and, for existing walls, an engineer. This page quotes no code section numbers.

Edition and adoption vary. Check the code your jurisdiction adopted.

Vertical cracks compared with other patterns

Myths about vertical cracks

Myth A vertical crack is always harmless.

Reality The same pattern can come from drying shrinkage or from settlement at a projection ². Never assume a specific crack is harmless.

Myth A vertical crack always means settlement.

Reality HUD notes many signs of masonry distress are wrongly blamed on settlement when moisture or thermal movement is the cause ².

Myth If it leaks it needs underpinning.

Reality A leak points to water. Underpinning is a footing repair. They are not the same problem.

Myth Caulking fixes it.

Reality A filler may stop a leak. It does not tell you why the crack opened, and it can hide change.

Myth One vertical crack is the whole story.

Reality Look at the whole house. Other cracks and door behavior add context.

Climate and soil context

Choosing your next step

Match what you see with a first move.

Related terms

Horizontal Foundation Cracks

Horizontal foundation cracks are cracks that run roughly level along a foundation wall, often across the middle of a block or poured basement wall.

Diagonal Foundation Cracks

Diagonal foundation cracks are cracks that slant across a foundation wall rather than running level or plumb.

Stair-Step Cracks in Brick and Block Walls

Stair-step cracks in brick and block walls are cracks that follow the mortar joints in a zigzag, rising like the steps of a staircase.

Foundation Movement Monitoring

Foundation movement monitoring is the practice of measuring a house at set intervals, with crack gauges, floor-level readings or survey targets, to learn whether the structure is moving, in which direction, and whether the movement is changing.

Differential Settlement

Differential settlement is uneven settlement, where one part of a foundation sinks more than another.

Cracks in Slab Foundations

Cracks in slab foundations are breaks in the concrete slab that forms a house floor and foundation, caused by shrinkage as the concrete dried, by temperature, by loads, or by movement of the soil beneath, and read as clues, not as a diagnosis.

Signs of Structural Foundation Damage

Signs of structural foundation damage are visible clues that a foundation or the ground under it may have moved, such as growing cracks, sticking doors, sloping floors or bowing walls, which call for a licensed engineer to interpret.

Also referenced from: Horizontal Foundation Cracks, Diagonal Foundation Cracks, Stair-Step Cracks in Brick and Block Walls, Cracks in Slab Foundations, Foundation Crack Width and Monitoring, Signs of Structural Foundation Damage