Screed faults and repairs
Screed Repair for Cracked, Curling and Hollow Floors
A crack in a screed is not always a failure, and a failure is not always a crack. The right repair starts with finding out why it happened.
Got a cracked or hollow screed?
Name, phone, email — we'll reply the same working day with a fixed price.
Or call our landline on 01392 237700
Does screed crack? Sometimes. Cement screeds shrink as they dry, anhydrite screeds can crack where restraint or a missing joint stops them moving, and a floor heated too early can open up along the pipe runs. Most of these cracks are fine hairlines; a few are a sign of something worse underneath.
Screed repair is about telling the two apart. A stable hairline crack can often be filled and the floor finished. A floor that rocks, sounds hollow or lifts at the edges usually needs the affected area cut out and re-laid, or a new screed over the top.
Common screed faults and usual repairs
| Fault | Usual approach |
|---|---|
| Fine shrinkage cracks in cement screed | Check they are stable, then fill with a resin repair before coverings |
| Cracks over doorways or at internal corners | Usually a missing joint; form a joint or bridge the crack in resin |
| Anhydrite screed cracking after first heating | Check the heat-up was gradual; repair once the floor is stable |
| Screed curling at the edges | Let drying even out, then grind or cut back and re-bed the edge |
| Hollow-sounding or debonded areas | Map the area, cut out and re-lay, or inject where suitable |
Cracked screed: when to fill and when to re-lay
Cracks in screed matter most under rigid finishes. Tiles and stone will follow a moving crack, while carpet may hide it. Before any repair we check whether the crack is still moving, whether the two sides are level, and whether the screed around it is bonded or hollow.
For the causes in detail, read our guides to cracked screed repair, shrinkage cracks in anhydrite, curling at screed edges and hollow-sounding debonded areas.
How a screed repair is assessed
- 1
Look and listen
Map cracks and tap the floor to find hollow areas.
- 2
Check the cause
Joints, edge strip, heating start-up, drying conditions and the base underneath.
- 3
Check moisture
A wet screed is repaired after it has dried, not before.
- 4
Choose the repair
Fill, joint, cut out and re-lay, or a new screed over the top.
Cement floor repair or a new screed?
- Small, stable cracks in an otherwise sound floor: repair in place
- Large hollow areas, crumbling surface or lifting edges: cut out and re-lay
- An old, uneven floor being renovated anyway: a new screed over the top
Assessing cracks before choosing repair or re-pour
The decision between repairing and re-pouring rests on three questions. Is the crack still moving? Are both sides at the same level? Is the screed either side still bonded to the base? A fine crack with level edges in a well-bonded floor is a surface defect. A crack with a step, or one running through an area that sounds hollow, points to a problem with the base, the joints or the bond, and filling it alone will not last.
It also helps to know the screed type and its age. A young cement screed may still be shrinking, so repairs are best left until drying has settled. An anhydrite screed that cracked after the first heat-up should be checked once the heating has been brought up gradually and the floor is stable.
Hollow and debonded areas
Tapping the floor with a hammer or dragging a chain across it shows up hollow areas by sound. These are places where the screed has lost contact with the base or the layer below. Small, stable areas under a flexible covering may not need work, but under tiles or stone a hollow patch can crack the finish. Larger or growing areas are usually marked out, cut back to sound screed and re-laid, so the new section sits on a firm, clean base.
Sealing or stitching fine cracks before coverings
Once a crack is confirmed as stable, it can be opened slightly, cleaned and filled with a low-viscosity resin so the two sides act as one again. Wider cracks can be stitched with resin and metal staples set across the line. Cracks that follow a joint position are often better turned into a formed joint, carried through to the covering, so the floor can keep moving there without damaging tiles.
Before any covering goes down over a repaired floor, the screed should be dry enough for that covering. See screed moisture testing for how readings are taken and what they are compared against.
When a levelling layer over a repaired base helps
Where a floor has several repairs, old patches at different heights, or is generally uneven, a new self-levelling screed over the repaired base can give one flat, continuous surface for the finished flooring. The base is made sound first, then the new layer is bonded or laid unbonded over a membrane depending on its condition. Our floor levelling page explains the depths and options.
If the damage is in the concrete slab beneath the screed rather than the screed layer itself, see our concrete floor repair page for assessment and preparation before a new floor build-up.
Frequently asked
Got a cracked or hollow screed?
Send photos, the floor area and the covering planned. We reply the same working day.