A screed floor is a layer of mortar or flowing material placed on top of the structural floor to create a flat, load-bearing base for the final floor finish. A screed evens out irregularities, embeds services (especially underfloor heating) and contributes to acoustic and thermal performance.
Types of screed
The most common types are:
- Sand-cement screed — the classic mix of sand, cement and water. Robust and suitable for almost any finish.
- Anhydrite (calcium sulphate) screed — a flowing screed that is very flat and excellent for underfloor heating.
- Cement-based flowing screed — a pumpable cement screed, flatter than a traditional sand-cement screed.
- Dry screed — built up from gypsum-fibre or OSB panels on an insulation layer, used in light retrofit projects.
Function
A screed can serve several roles:
- Levelling — providing a flat base for tiles, parquet, laminate or vinyl
- Embedding services — underfloor heating, pipes and ducts
- Acoustic insulation — as a floating screed on a soft layer
- Thermal insulation — with insulation underneath
Construction
A bonded screed sits directly on the structural slab and is bonded to it. A screed on a separating layer has a membrane between the screed and the slab to prevent bonding. A floating screed rests on insulation and is separated from walls and columns by edge strips — this prevents impact-sound transmission.
| Type | Bond | Application |
|---|---|---|
| Bonded | On structural slab | Workshops, no acoustic requirements |
| Separating layer | On membrane | Renovation, damp situations |
| Floating | On insulation | Housing, acoustic requirements |
Things to watch
- Drying time — sand-cement: roughly one day per mm; anhydrite is faster
- Shrinkage — control joints every 20–30 m² or in narrow strips
- Moisture check — before laying the finish, especially for parquet and vinyl
- Expansion joints — required with underfloor heating over large areas
Related terms
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