Cracks in Concrete Walls and Floors: When Should You Be Concerned?

Discovering a crack in a concrete wall or floor can be worrying. Although some cracks are caused by normal drying or minor movement, others may indicate water ingress, deterioration or a more significant structural problem.

The appearance of the crack alone does not always reveal the cause. Its location, direction, width and whether it is changing over time all need to be considered before deciding on the most appropriate repair.

At Shield Waterproofing and Preservation, our specialists assess concrete damage, identify the likely cause and recommend a repair designed for the particular structure. Request a concrete repair survey.

Why Does Concrete Crack?

Concrete is an extremely strong and durable material, but it is not completely resistant to movement or deterioration.

Common causes of cracking include:

• Shrinkage as newly placed concrete dries
• Temperature changes causing expansion and contraction
• Movement or settlement within the building
• Excessive loading or pressure
• Poorly formed construction joints
• Water entering through the concrete
• Corrosion of reinforcement within the structure
• Damage caused by previous building work

A crack may have more than one contributing cause. This is why simply filling the visible opening without investigating the surrounding structure may not provide a lasting solution.

Are Hairline Cracks in Concrete Serious?

Fine or hairline cracks can develop as concrete cures and dries. A small, stable crack does not necessarily mean that the structure is unsafe.

However, even a fine crack should not automatically be dismissed, particularly when it is found in a basement, retaining wall, concrete floor, car park or another area exposed to moisture or structural loading.

It is sensible to monitor the crack and seek professional advice if it changes, returns after being repaired or is accompanied by other signs of deterioration.

Warning Signs That a Concrete Crack Needs Investigating

You should consider arranging an inspection when:

• The crack is becoming wider or longer
• One side of the crack is higher or further forward than the other
• Water is entering through the crack
• The surrounding concrete is crumbling or breaking away
• Rust staining is visible on the surface
• Reinforcement can be seen inside the concrete
• The floor appears uneven, sunken or unstable
• Several cracks have appeared in the same area
• A previous repair has failed
• The crack is close to a supporting wall, column or structural opening

These signs do not necessarily confirm that a building is unsafe, but they do indicate that the problem should be properly assessed rather than covered with filler or paint.

Can Water Enter Through Cracks in Concrete?

Cracks and construction joints can provide a direct route for water to enter a building.

This is particularly common in basements and other below-ground structures, where water pressure from the surrounding ground may force moisture through even relatively narrow openings.

Surface sealants may temporarily disguise the problem, but they are unlikely to succeed if water pressure or continuing movement has not been addressed.

Specialist crack injection techniques can be used to seal certain water-bearing cracks and joints. Where the problem forms part of wider water ingress, a complete basement waterproofing solution may also need to be considered.

How Are Cracks in Concrete Repaired?

The correct repair depends on the cause, condition and purpose of the concrete.

Possible repair methods include:

Epoxy Crack Injection

Low-viscosity epoxy resin can be injected into suitable cracks to bond damaged sections of concrete or masonry back together. This method may be used for fine, stable cracks where a structural bond is required.

Shield recently used this technique during an epoxy crack injection project in Bath.

Polyurethane Resin Injection

Specialist polyurethane resins can be used to seal cracks and joints affected by active water ingress. The resin fills the available space and creates a barrier against further water penetration.

Concrete Patch Repairs

Where sections of concrete have broken away or deteriorated, the damaged material may need to be removed before a suitable repair mortar is applied.

If reinforcement has been exposed, it may also require cleaning and protection before the concrete is reinstated.

Structural Strengthening

More substantial cracking may require additional structural repairs, reinforcement or strengthening.

Where movement, settlement or loading has caused the damage, the underlying issue must be addressed as part of the repair plan.

Why Surface Filling Is Not Always Enough

Filling a crack from the surface may improve its appearance, but it does not necessarily repair the problem within the concrete.

A surface-only repair can fail when:

• Movement is continuing
• Water pressure remains behind the concrete
• The crack extends deeper into the structure
• Reinforcement is corroding
• Loose or contaminated concrete has not been removed
• The wrong repair material has been used

An effective repair should deal with the cause and depth of the damage, not just the section that can be seen.

Professional Concrete Repairs

Shield Preservation provides specialist concrete repair services for domestic, commercial and below-ground structures.

Every project begins with an assessment of the damage and the surrounding conditions. This allows our team to determine whether the crack is cosmetic, associated with water ingress or part of a wider structural problem.

Depending on the findings, the recommended work may include crack injection, concrete reinstatement, reinforcement treatment, waterproofing or more extensive structural repairs.

Arrange a Concrete Repair Survey

Cracks in concrete should not be ignored, particularly if they are changing, allowing water into the property or accompanied by crumbling concrete, rust staining or movement.

A professional inspection will help establish what has caused the cracking and whether repair work is required.

Request a concrete repair survey with Shield Waterproofing and Preservation or call 0800 098 2780 to discuss your property with our team.