Existing slab assessment and repair
Concrete Floor Repair Before Screeding
A new screed needs a suitable base. Assess cracks, broken patches and joint edges in the existing concrete before deciding what to repair or cover.
Discuss a damaged concrete base
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Concrete floor repair concerns the slab beneath the screed or floor covering. A chipped edge, a damaged patch and a crack running through the slab can need different approaches, even when they look similar from above. The starting point is the cause and extent of the damage, not simply a choice of filler.
For a floor being prepared for screeding, the repair must work with the proposed build-up. It should leave a sound base without hiding movement, trapping unresolved moisture or creating an incompatible patch beneath the next layer. Share photographs and the planned finish so the repair and screeding requirements can be considered together.
Concrete damage or a screed fault?
Many floors have a concrete slab, a separate screed and a covering. A crack visible at the top does not identify which layer has failed. Establishing the build-up helps avoid treating a screed defect as slab damage, or assuming a new screed will solve a problem in the concrete underneath.
Our screed repair service covers cracks, curling and hollow areas in the screed layer. This page focuses on the existing concrete base: broken surface patches, damaged joint edges and cracks that need assessment before a new floor is laid. Where the floor construction is unclear, that distinction should be established before selecting materials.
Assessing cracked concrete floor repair
The important questions are whether a crack is stable, whether its edges are level and whether the surrounding concrete is sound. Its position relative to joints, thresholds and changes in construction can help explain why it appeared. Photographs are useful, but they do not establish whether the slab is still moving.
Cracks with a step, continuing movement or signs of settlement need investigation rather than a cosmetic fill. Where the slab's structural condition is in doubt, an appropriate structural assessment should guide the next step. Filling a crack does not correct the reason it formed, and a levelling screed is not a structural repair to the slab.
Repairing local patches and joint edges
Local damage can require loose or weak concrete to be removed back to sound material, followed by a compatible repair product. The product's permitted depth, substrate preparation and curing requirements all matter. A patch needs to suit the floor's use and the primer, screed or covering that will follow it.
A damaged movement joint is a different detail from a stable surface crack. The joint may need to remain able to move and continue through the next layer. Rigidly filling it without considering the floor design can transfer movement into a new crack alongside the repair.
From assessment to the next floor layer
- 1
Record the damage
Mark affected areas and share photographs showing both close-up details and the surrounding floor. Note any changes over time, previous repairs and signs of damp.
- 2
Define the repair
Separate stable local defects from wider movement or weak concrete. Agree repair materials, preparation and joint details against the intended build-up.
- 3
Prepare and repair
Remove unsound material and contamination as required by the repair system. Keep repair edges and depths within its instructions rather than feathering an unsuitable product too thinly.
- 4
Allow for the following layer
Respect curing requirements and check compatibility before priming or screeding. A repaired area may be ready for traffic before it is ready for the next floor product.
Planning a repair alongside screeding
Repair and levelling do different jobs. A repair restores a suitable local substrate; a levelling layer addresses the floor height and flatness. If several sound repairs leave an uneven surface, floor levelling may form part of the next stage, but only after the base has been assessed.
Cost and programme depend on the extent and depth of damage, access, removal of existing coverings, preparation and curing. Include the floor area, planned use and any specification in your enquiry. Agree who undertakes each stage and what condition the slab must be in before screeding begins, so separate trades do not leave a gap in the preparation scope.
Frequently asked
Discuss a damaged concrete base
Send photographs, the affected floor area and the screed or covering planned so the repair requirements can be considered before the next layer.