Concrete Crack Repair: Methods, Materials & Step-by-Step Fix

Cracks in concrete can affect appearance, water resistance and, in some cases, structural performance. Effective concrete crack repair starts with correctly identifying the crack. Hairline and shrinkage cracks may need a suitable concrete crack filler, while wider or active cracks may require professional assessment and a repair system.

For plastered surfaces, Dr. Fixit Crack-X is designed for cracks up to five millimetres. Dr. Fixit Crack-X Shrinkfree is intended for plaster cracks up to 10 millimetres. Neither product is intended for structural cracks in concrete or slabs.

 

Types of Concrete Cracks
 

Understanding the type of cracks you’re dealing with helps you choose the right repair approach.
 

Hairline cracks
 

Hairline cracks are narrow surface cracks. They can occur in plaster and cementitious surfaces because of drying, shrinkage, or minor movement. Small, non-structural cracks can allow moisture to enter exposed surfaces. A flexible filler can help seal suitable surface cracks before further waterproofing treatment.
 

Shrinkage cracks
 

Shrinkage cracks can develop as cementitious materials lose moisture and cure. A suitable non-shrink crack filler, such as Dr. Fixit Crack-X Shrinkfree, can help address these cracks.
 

Structural cracks
 

Structural cracks can involve concrete members, slabs or other load-bearing elements. Widening cracks, recurring cracks, or cracks accompanied by movement need closer assessment. Do not treat a suspected structural crack as a simple surface defect. A qualified professional should assess the cause before recommending repairs or renovations. 

 

How to Repair a Concrete Crack (Step by Step)
 

The right concrete crack repair depends on the crack and substrate. For suitable non-structural plaster cracks, the typical sequence is to clean the surface, prepare the crack, apply the appropriate filler, and finish the surface. Structural cracks need professional assessment and may require injection or a polymer-modified repair system.
 

Non-structural cracks
 

For non-structural cracks, follow this sequence through a trained applicator:
 

1. Inspect the crack: Check its width, location, and visible movement.
    
2. Clean the surface: Remove dust, loose particles, grease, etc.
    
3. Prepare the crack: Where specified, form a suitable V-shaped groove.
    
4. Apply the filler: Press the selected crack-filling inside the crack.
    
5. Finish the surface: Level the repair and let it dry.
    
6. Protect the surface: Use the appropriate waterproofing system where moisture exposure is involved.
    

Structural Cracks
 

Structural crack repair begins with diagnosis, not simply filling the visible opening. A professional may assess the crack pattern, width, location, and signs of movement. Depending on the diagnosis, the repair system may involve injection, repair mortar, or other structural repair techniques. Severe structural damage may also require complete renovation. 

 

Materials & Tools
 

The materials depend on the crack and substrate. Common requirements can include:

Dr. Fixit Pidicrete URP is a styrene-butadiene co-polymer latex that improves bonding between old and new concrete or plaster. It also enhances the water resistance of repair mixes. For product-specific application requirements, always follow the relevant technical data sheet.

 

When to Call a Structural Expert
 

Professional assessment is important when the crack appears active or is associated with structural movement.
 

Red flags
 

Seek professional assessment when you notice:
 

• Cracks that continue to widen or return
   
• Cracks across concrete slabs or structural members
   
• Significant displacement along the crack
   
• Multiple connected cracks across an area
   
• Water ingress associated with a concrete crack
   
• Cracks accompanied by visible deterioration or spalling
   

Waterproofing also matters where cracks allow moisture ingress. External walls, balconies and other exposed surfaces can need crack treatment followed by an appropriate waterproof exterior coating system. For professional guidance, fill out the form below to connect with a Dr. Fixit waterproofing expert.

 

Frequently asked questions
 

How do I repair a crack in concrete?

First, identify whether the crack is non-structural or structural. You can fill suitable surface cracks after proper preparation. Suspected structural cracks need professional assessment before repair.


What is the best product for concrete crack repair?

No single product works for every crack. Dr. Fixit Crack-X is intended for suitable plaster cracks up to five millimetres, while Crack-X Shrinkfree is intended for plaster cracks up to 10 millimetres. Structural cracks require a different assessment and repair system.


How do I tell a structural crack from a non-structural one?

Look at the crack's location, width, pattern, and movement. Cracks affecting slabs or structural members need professional assessment. Do not assume that a wide or recurring crack is only superficial.


Can I fix concrete cracks myself?

The repair method depends on the crack and substrate. For safety, have a qualified professional assess suspected structural cracks. Follow the manufacturer's technical guidance when applying products.


How do I stop cracks from coming back?

Address the underlying cause rather than only filling the visible crack. Correct surface preparation, suitable repair materials and appropriate waterproofing can help reduce recurring moisture-related problems.


Does waterproofing help prevent crack-related seepage?

Waterproofing can help manage moisture ingress through suitable surfaces after cracks have been correctly treated. The right system depends on the substrate, exposure, and water source.