Guides · checked 29 October 2026
Screed vs concrete
Which layer carries the floor, which levels it, and which one your job needs.
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- Sources under every figure
Figures checked against each source on 29 October 2026. How we check
Concrete and screed are both cement, aggregate and water, but they do different jobs. A concrete slab is structural: it carries the floor. A screed is the layer on top that gives a flat, level surface for the floor finish.
BS 8204-1 defines a levelling screed as one finished to a defined level to receive the final flooring. Concrete uses larger aggregate; a fine concrete screed tops out at 10 mm aggregate.
The difference
| Concrete slab | Screed | |
|---|---|---|
| Job | Structural: floor slabs and foundations | Levelling: a flat surface at the right height for the floor finish, or a wearing surface |
| Aggregate | Larger, coarse aggregate | Sand, or up to 10 mm for a fine concrete screed |
| Where | On hardcore and membranes, or as a suspended slab | On the slab, or floating on insulation |
| Standards | Concrete standards | BS EN 13813 for screed material; BS 8204 for laying |
Sources: Flowcrete, Concrete vs floor screeds (12 June 2023); Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023). Checked 29 October 2026.
- Floor finish
- Screed Levelling layer, here floating.
- Insulation
- Damp-proof and radon membrane Radon membrane required in High Radon Areas since 1 July 1998 (EPA).
- Concrete slab Structural.
- Hardcore Compacted fill under the slab.
Source: EPA, Radon advice for builders. Checked 29 October 2026.
Why not just pour the slab flat
A slab can be finished flat and level, and some floors, such as warehouses, are left as exposed concrete. In houses the screed does other jobs: it covers insulation and heating pipes, provides falls, and sets an exact level for the floor finish, the Mineral Products Association notes.
In the UK, NHBC asks for a ground-bearing slab at least 100 mm thick, including any monolithic screed.
Sources: Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023); Designing Buildings Wiki, Screed (last edited 15 September 2020); NHBC Standards 5.1.17, ground floor slab and concrete (UK). Checked 29 October 2026.
When people mean concrete but need screed
- Levelling an existing floor before tiles or timber: a screed, or a levelling compound for a few mm.
- Covering underfloor heating: a screed.
- A new ground floor: a concrete slab first, then usually insulation and a screed.
Questions people ask
Is screed the same as concrete?
No. Concrete is structural and has larger aggregate. Screed is a levelling layer of sand and cement, or a flowing screed, laid on the slab or on insulation.
Can I use concrete instead of screed?
For a structural slab, yes. For covering insulation and heating pipes, and for an exact level under a floor finish, a screed does the job.
How thick is a concrete floor slab?
In the UK, NHBC asks for at least 100 mm for a ground-bearing slab, including any monolithic screed. Your engineer's design sets it.
Does a concrete slab always need a screed on top?
Not always. Designing Buildings Wiki notes concrete floors are generally covered with screed unless they're left exposed, as in some warehouses.
Sources (4)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Flowcrete, Concrete vs floor screeds: flowcrete.eu
- Mineral Products Association, Mortar Data Sheet 22: Screeds: mortar.org.uk
- Designing Buildings Wiki, Screed: designingbuildings.co.uk
- NHBC Standards 5.1.17, ground floor slab and concrete (UK): nhbc-standards.co.uk
Get your floor priced
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