Finding a crack in a wall can be worrying for any property owner. Some cracks are caused by normal drying, temperature changes or minor settlement. Others may indicate foundation movement, poor construction, water damage or excessive pressure on part of the structure.

Appearance alone cannot confirm whether a crack is harmless or serious. However, its location, direction, width and rate of change can help determine whether professional assessment is needed.

Why Do Buildings Develop Cracks?

1. Normal Drying and Shrinkage

Concrete, plaster and other materials contain moisture when first applied. As they dry, they may shrink slightly and develop fine surface cracks, particularly in newly plastered walls, concrete floors, ceiling finishes and joints between different materials.

2. Natural Building Settlement

A newly constructed building may settle slightly as its weight adjusts to the soil beneath it. Minor settlement can produce small cracks around doors, windows or wall joints. Uneven or continuing settlement is more concerning because it can place stress on walls, floors, columns and foundations.

3. Poor Foundation Construction

Foundation problems can arise from inadequate soil investigation, poorly compacted ground, insufficient foundation depth, weak concrete, incorrect reinforcement or building alterations made without structural assessment.

4. Poor Drainage

Water gathering around a building can weaken surrounding soil and contribute to foundation movement. Common causes include blocked drains, broken underground pipes, roof water discharging beside the building, flooding and surfaces sloping towards the property.

5. Expansion and Contraction

Building materials expand and contract as temperature and moisture conditions change. Without adequate movement joints, repeated expansion and contraction may cause cracks in walls, concrete surfaces and external finishes.

6. Water Leakages

A concealed plumbing leak, damaged roof or broken drainage pipe can weaken plaster, concrete, timber and surrounding soil. Moisture can also corrode reinforcement inside concrete, causing the surrounding concrete to crack or break away.

7. Excessive Structural Load

Adding another floor, installing heavy equipment or removing a load-bearing wall changes how weight is distributed. Alterations carried out without structural assessment can overload foundations, beams, columns, walls or floor slabs.

8. Poor Workmanship or Materials

Incorrect mixtures, inadequate curing, poor reinforcement placement and weak construction practices can contribute to cracking months or years after completion.

Common Types of Building Cracks

Hairline Cracks

Hairline cracks are very narrow surface cracks, often found in plaster, paint or concrete finishes. They may result from drying shrinkage, minor temperature changes, poor plastering or slight settlement.

Monitor a hairline crack if it becomes longer, begins to widen, returns after repair, allows water into the building or appears in several connected locations.

Vertical Cracks

Vertical cracks move upward and downward along a wall. A narrow stable crack may be caused by shrinkage or minor settlement. A wide vertical crack extending through several floors or visible on both sides of a wall requires investigation.

Horizontal Cracks

Horizontal cracks can indicate pressure against a wall, structural movement or inadequate support. Cracks in foundations, retaining walls, columns or load-bearing walls should not be ignored, especially if the wall is bulging, leaning or separating.

Diagonal Cracks

Diagonal cracks commonly appear near corners of doors and windows. They may indicate that one part of the building is moving differently from another, possibly because of uneven settlement.

Stair-Step Cracks

Stair-step cracks follow the joints between blocks or bricks. They can indicate movement within the wall or foundation, particularly when wide, growing or visible on both the interior and exterior.

Cracks Around Doors and Windows

Openings create locations where stress can concentrate. Seek closer assessment when cracks grow, several openings are affected, doors no longer close properly, frames become distorted or gaps develop between frames and walls.

Ceiling Cracks

Ceiling cracks may result from joint movement, moisture damage, poor installation or structural movement. A ceiling needs urgent attention if it is sagging, soft, water-stained, pulling away or making cracking sounds.

Floor and Concrete Slab Cracks

More serious floor cracks may be accompanied by uneven surfaces, sinking sections, broken tiles, water entry, gaps between floors and walls, or a height difference on opposite sides of the crack.

Warning Signs That a Crack May Be Serious

How to Monitor a Crack

What Property Owners Should Not Do

Do Not Keep Filling a Recurring Crack

A crack that repeatedly returns may have an unresolved cause. Filler and paint can hide evidence without solving the underlying problem.

Do Not Ignore Water Around the Foundation

Repair leaking pipes, blocked drains and poorly directed roof water promptly. Water can change the condition of the ground supporting the building.

Do Not Make Structural Alterations Without Approval

Do not remove walls, columns, beams or major building sections without professional assessment. A wall that looks ordinary may be supporting the structure above it.

Do Not Rely Only on Online Photographs

Two cracks can look similar but have completely different causes. Proper assessment may require physical inspection, measurement, drainage investigation, foundation examination, soil assessment, structural calculations and review of building plans.

When Should You Call a Structural Engineer?

• A crack is growing quickly.
• It passes through a beam or column.
• Several areas of the building are affected.
• A floor is sinking or sloping.
• A wall is leaning or bulging.
• Doors and windows suddenly stop closing.
• Concrete reinforcement is exposed.
• The property has suffered flooding or major water damage.
• The building has been altered or extended.
• You are uncertain about the seriousness of the problem.

Why Early Inspection Matters

A small crack may be inexpensive to correct when detected early. If the underlying cause continues, the damage can spread to other parts of the property.