Liquid screed is widely used to produce flat, smooth floors, but cracks can occasionally develop while it dries. In many cases these are small hairline cracks that form naturally as the screed cures. While these are often harmless, larger or straight cracks may suggest movement or stress and should be assessed before the final floor finish is installed.
Common causes
Shrinkage during drying
As screed cures and moisture evaporates, it naturally contracts slightly. This process can create very fine hairline cracks.
Drying too quickly
Heat, strong airflow, open windows, or early use of underfloor heating can cause the top layer to dry too fast compared with the lower layers.
Poor bonding to the subfloor
If the base surface is dusty or contaminated, the screed may not bond properly, which can lead to movement and cracking.
Lack of expansion joints
Screed needs room to expand and contract. Without perimeter edging or movement joints, tension cracks can appear.
Incorrect water content
Too much water in the mix weakens the screed and increases shrinkage.
Insufficient screed depth
Very thin layers can curl or crack more easily than properly installed screeds.
Hairlines vs structural cracks
Very fine cracks are normally cosmetic and rarely cause problems with flooring installation. Cracks wider than 1–2mm or those running across the floor in straight lines should be inspected.
Fixes
Small hairline cracks may not need repair.
Moderate cracks can be ground out and filled with resin repair products.
Structural cracks may require stitching or epoxy injection.
If the screed has detached from the base, sections may need to be replaced.
Preventing repeats
A stable base, correct screed thickness, perimeter edging, controlled curing conditions, and gradual heating start-up all help prevent cracking.
Why choose Floor Screeding Surrey?
Floor Screeding Surrey provides professional screed installation and repair services throughout Surrey with experienced installers and clear advice.