A floor screed must be level to support the final floor covering properly. If it isn’t, problems such as cracked tiles, uneven flooring, or trip hazards may occur. Screed is installed over the base slab to create a flat surface before floor finishes are applied.
In the UK, floor flatness is assessed using Surface Regularity (SR) measured with a 2-metre straightedge:
- SR1: up to 3mm deviation
- SR2: up to 5mm deviation
- SR3: up to 10mm deviation
Liquid screeds commonly achieve SR2 or better, while traditional sand and cement screeds may fall within SR3 if not carefully installed.
Why flatness matters
An uneven screed can lead to several issues.
- Floor coverings may crack or fail due to uneven support.
- High areas may wear faster while low areas trap debris or moisture.
- Uneven surfaces can create trip hazards.
- Underfloor heating may distribute heat unevenly.
- Flooring warranties may become invalid if SR tolerances are not met.
Common causes
Uneven screeds are often caused by poor preparation, incorrect mixing ratios, staged pours creating ridges, lack of spiked rolling, or poor site conditions during installation.
Fixing an uneven screed
Minor imperfections can often be corrected by grinding or applying a thin levelling compound. In more serious cases, sections of screed may need to be removed and replaced.
Why choose Floor Screeding Surrey?
Floor Screeding Surrey provides professional screeding services across Surrey, ensuring floors meet the required SR tolerances.