What Are the Main Types of Cracks in Walls?

Wall cracks fall into a handful of visible types: hairline, vertical, horizontal, diagonal, stair-step, map or crazing, cracks around doors and windows, and cracks that come with wall bowing or displacement.

Crack shape tells you where to investigate, but it does not establish the cause by itself. The table and atlas below list each type, what can cause it, and what to check next.

Why Wall Crack Pattern Alone Does Not Tell You the Cause

Two cracks with the same shape can come from different causes. ACI 224.1R and USACE both stress that a crack is a symptom, and the mechanism behind it decides the repair.

• A diagonal crack in a concrete block wall can come from block shrinkage or from settlement.
• A vertical shrinkage crack can look like one from differential settlement.
• A horizontal crack from construction effects can look like one from lateral soil pressure.

HUD’s inspection guide discusses shrinkage cracking in concrete-block foundation walls alongside settlement cracking, which is why context, such as movement and the rest of the building, matters.

How to Describe a Wall Crack Correctly

Good descriptions make diagnosis easier. Record these details for any crack:

• Direction.
• Length.
• Width.
• Taper, meaning wider at one end.
• Depth or continuity, where visible.
• Displacement.
• Location on the wall.
• Moisture.
• Deformation of the adjacent wall.

Later sections use these terms. A description like “vertical, 4 feet long, tapering, with a small offset near the floor” tells a professional far more than “a big crack.”

Stable, Active and Cyclical Cracks

Behavior is one of the most useful ways to classify a crack. ACI treats whether a crack is active or dormant as an important consideration when choosing repairs.

• Stable or dormant: little or no ongoing change.
• Active: still widening, extending, or moving.
• Cyclical: opens and closes with temperature or seasons.

HUD notes that cracks may open and close seasonally and describes joint movement indicators for documenting behavior. USACE adds that a crack of unknown cause should be treated as active.

Structural vs. Nonstructural Wall Cracks

A screening-level split helps. Nonstructural cracks mainly affect appearance, water resistance, and durability. Structural concern rises when cracking comes with displacement, bowing, load-path problems, or foundation movement.

Do not classify by width alone. FEMA’s structural training notes that most normal concrete develops narrow, hairline cracks from shrinkage, temperature change, and predictable structural behavior, so some cracking is expected.

To decide how worried to be, read When to Worry About Cracks in Walls.

Hairline Cracks in Walls

Hairline cracks are very fine, and they are the most common. They include fine shrinkage cracks, finish-coat cracks, early concrete shrinkage, and temperature effects.

They deserve more attention when they keep growing, leak, spread over a wide area, show signs of reinforcement corrosion, or sit in a structural member.

Vertical Cracks in Walls

Vertical cracks can come from drying shrinkage, thermal movement, settlement, or construction joints and details. Many vertical cracks in concrete foundation walls are relatively benign when stable.

Displacement or progressive movement changes the concern level, so check for offset and measure over time.

Horizontal Cracks in Walls

Horizontal cracks need careful attention. They can come from lateral soil pressure, wall bending, frost or heaving, backfill or construction pressure, and movement along masonry joints.

HUD describes sweeping or horizontal cracking in foundation walls from improper backfilling, vibration, or swelling or freezing of saturated soil, and treats wall bowing and leaning under lateral loading as a concern.

A horizontal crack with a measurable bow is very different from one with no deformation.

Diagonal Cracks in Walls

Diagonal cracks have several possible causes: differential settlement, stress concentration, shrinkage, openings, and load redistribution.

FEMA’s structural training says shrinkage can produce diagonal cracks at the re-entrant corners of openings such as windows and doors. HUD links settlement to diagonal patterns, so the same shape can mean different things.

The direction of taper may hint at movement, but it does not give a definitive diagnosis.

Stair-Step Cracks in Brick and Concrete Block Walls

Stair-step cracks follow the mortar joints in brick and concrete block. FEMA notes that cracks in unreinforced masonry tend to follow the weaker mortar instead of going through the units.

Causes include differential foundation movement, shrinkage, and masonry construction issues. HUD notes that block shrinkage can produce patterns resembling settlement, so context is essential.

Map Cracks and Crazing

Map cracks form a network of fine lines. NRMCA defines crazing as a network of fine random cracks caused by shrinkage of a paste-rich surface layer, and it is sometimes called shallow map or pattern cracking.

• Superficial crazing on cementitious finishes.
• Broader map cracking linked to deterioration of the material.

Do not label all map cracking as alkali-silica reaction (ASR). Crazing is usually a surface finishing issue, and it is more visible when the surface is drying after being wet.

Cracks Around Doors and Windows

Cracks at door and window corners are common because stress concentrates at those re-entrant corners. Possible causes include framing movement, settlement, lintel or header issues, and finish cracking.

A sticking door or window changes the interpretation. Cracks plus functional changes point more strongly toward movement.

Cracks at Wall-to-Ceiling or Wall-to-Floor Connections

Cracks where walls meet ceilings or floors often come from framing movement, settlement, truss movement, differential movement between materials, or foundation displacement.

Drywall cracking here is usually minor, but a gap that keeps opening or comes with sloping floors deserves a closer look.

Cracks in Poured Concrete Walls

Poured concrete walls crack from shrinkage, restraint, settlement, thermal effects, lateral pressure, and corrosion. FEMA notes that straight shrinkage cracks often occur every 5 to 20 feet in long reinforced walls, depending on reinforcement, pour joints, and curing.

For general mechanisms, read Why Is My Concrete Cracking?. For stable cosmetic cases, see the repair-before-painting guide linked in the final table.

Cracks in Concrete Block Walls

Concrete block walls crack in mortar joints, horizontally along bed joints, vertically through units, and in stair-step patterns. The Concrete Masonry & Hardscapes Association explains that concrete masonry undergoes volume changes from moisture, thermal movement, and carbonation, which is why control joints are used.

HUD discusses block shrinkage and settlement separately, but their patterns can overlap. Lateral wall pressure can also cause horizontal bed-joint cracks.

Cracks in Brick and Masonry Walls

Brick and masonry cracks include stair-step mortar-joint cracks, vertical cracks, expansion-related cracks, and lintel-related cracking.

Clay brick expands with moisture, and expansion joints are used mainly with clay masonry. Brick veneer movement and structural foundation movement are not automatically the same problem.

Cracks in Plaster and Drywall

Plaster and drywall cracks are finish cracks. Common causes include shrinkage, joint movement, framing movement, moisture, and foundation movement reflected through the finish.

They sometimes reveal building movement, but they are not themselves structural concrete defects. The table compares patterns by wall material.

Shrinkage Cracks

Shrinkage cracks come from drying and contraction. ACI lists shrinkage among the major causes of concrete cracking.

FEMA notes they usually appear within about 60 days of the pour as concrete dries, and reinforcing steel helps keep them small. They often develop early, show limited displacement, and are frequently stable after initial drying.

The Concrete Shrinkage Calculator gives background on shrinkage strain.

Settlement Cracks

Settlement cracks come from differential support movement, where one part of a foundation moves more than another. Contributing factors include poorly compacted fill, bearing soil movement, erosion, moisture changes, and nearby excavation.

Repairing settlement is different from filling the crack. See How to Fix Structural Cracks in Walls for stabilization methods.

Thermal and Seasonal Movement Cracks

Temperature and seasonal changes make concrete and masonry expand and contract. HUD notes that temperature-related cracks may open and close with the seasons.

FEMA adds that temperature cracks occur in roughly the same pattern as shrinkage cracks and are difficult to tell apart. Flexible repair may suit these, but the detailed procedures belong on other pages.

Lateral-Pressure Cracks

Basement and retaining walls resist soil pushing in from outside. Saturated soil, expansive soil, frost, and improper backfilling can all raise that pressure.

Horizontal cracking plus wall bowing warrants a more careful evaluation, because the wall may be bending under load.

The Foundation Wall Thickness Chart offers general background, not design values.

Reinforcement Corrosion Cracks

Corrosion cracks follow the reinforcing steel. The steel corrodes, the rust expands, and cracks form along the bar. Delamination and spalling may follow.

See Concrete Spalling and Concrete Delamination for the surface effects, and the Concrete Cover Chart for why cover matters.

Moisture and Freeze-Related Cracks

Water and freezing can crack walls in several ways: frost heave, repeated moisture movement, freeze-thaw effects, and water infiltration.

HUD illustrates bowed foundation walls, horizontal cracking, and floor movement in frost-heave conditions. White deposits along a crack point to a moisture pathway, covered in Concrete Efflorescence.

Load-, Design- and Construction-Related Cracks

Some cracks come from the design or construction itself. These include overload, insufficient support, poor detailing, openings, construction sequence, and restrained movement.

ACI includes design, detailing, and construction procedures among the factors that affect cracking. The table pairs common patterns with likely mechanisms.

Crack Width, Taper and Displacement: What Each Means

Width, taper, and displacement each say something different. Width is useful for monitoring, taper may suggest the direction of relative movement, and displacement shows that surfaces have moved relative to each other.

There is no universal dangerous width. A narrow crack can be moving, and a wide one can be old and stable.

How Crack Location Changes the Diagnosis

Where a crack sits can be as useful as its direction. Think about these locations:

• Near foundation corners.
• At openings.
• Mid-wall.
• Near the floor line.
• Along reinforcement.
• At joints.
• Near beams and columns.

Cracks at beam and column connections deserve more careful evaluation than those in a finish layer. Combine location with pattern and behavior.

How to Identify and Monitor Your Wall Crack

Use this workflow to identify and track a crack, then pick the right next guide:

1. Identify the wall material.
2. Identify the crack pattern.
3. Measure the width.
4. Check for displacement.
5. Photograph it with a scale.
6. Inspect for moisture.
7. Look for wall bowing.
8. Check doors, windows, and floors.
9. Monitor change over time.
10. Choose the correct next guide.

HUD recommends monitoring movement and describes commercially available joint movement indicators. FEMA’s training material also describes simple marking methods, such as drawing an X across the crack, and plastic crack gauges. Its context is disaster-response training, so its collapse criteria should not be applied to ordinary home inspections.

Estimate filler only after the repair method is established. The calculator is meant for suitable sealing and filling applications.

Types of Wall Cracks FAQs