Short answer: a traditional floor screed is usually mixed at 1 part cement to between 3 and 5 parts sharp sand by volume, with 1:4 a common choice. It is laid semi-dry, with only enough water to hold together when squeezed, then compacted and finished. Stronger mixes are used for thinner or more heavily loaded screeds.
Why semi-dry?
Extra water makes a screed easier to spread but weaker, more prone to shrinkage cracking, and slower to dry. A semi-dry, “earth-damp” mix compacted properly gives a dense, strong floor.
The right sand
Screeds use sharp sand (grit sand), which has angular grains that lock together. Soft building sand, used for bricklaying, makes a weak, crumbly screed.
Fibres, additives and pre-mixed screeds
- Polypropylene fibres help control early shrinkage cracking.
- Admixtures can improve workability without adding water, or speed up drying.
- Factory-batched or pre-blended screeds give a consistent mix every time, which matters on larger floors.
Common mistakes
- Too much water, for an easy finish
- Building sand instead of sharp sand
- Inconsistent mixing between batches
- Poor compaction, especially at edges and around pipes
We lay pumped, properly compacted sand and cement screeds across Essex. Read why the depth matters as much as the mix.
Written by Ben Phillips, director of Chelmsford Floor Screeding Ltd, floor screeding contractors based in Billericay with 20+ years of experience across Essex and London. More about us.