Screed is the layer of material, typically a cementitious mix, applied to a structural concrete floor slab or existing substrate to create a smooth, level surface ready for finished floor coverings. It is an essential component of most UK ground floors and any floor incorporating underfloor heating, and the choice of screed type significantly affects both cost and programme.
What Is Screed Used For?
Screed serves several functions:
- Levelling an uneven or rough concrete slab to receive tiles, stone, engineered timber, vinyl or carpet
- Encapsulating underfloor heating pipes or electric mat systems
- Achieving the correct finished floor level in new builds and extensions
- Providing a consistent base that allows floor coverings to be bonded or laid evenly
Screed is distinct from concrete: concrete is a structural material; screed is a wearing or receiving surface. Screed should not be relied on for structural load-carrying.
Types of Screed
| Type | Description | Thickness | Drying Rate | Cost (per m², installed) |
|---|---|---|---|---|
| Traditional sand-and-cement (unbonded) | Mixed on site or bagged; laid over a slip membrane | 65–75 mm | 1 day per mm | £15–£22 |
| Traditional sand-and-cement (bonded) | Laid directly onto primed concrete | 25–40 mm | 1 day per mm | £18–£25 |
| Calcium sulphate (anhydrite) liquid screed | Pumpable; self-compacting; contains no cement | 35–50 mm | 1 day per mm + drying aids | £18–£341 |
| Self-levelling compound (SLC) | Thin repair or finishing layer; polymer-modified | 3–10 mm | 24–48 hrs typically | £12–£25 |
| Rapid-drying screed | Modified binders that accelerate moisture release | 40–65 mm | 1 day per 1.5 mm | £28–£45 |
| Heated screed (UFH encapsulant) | Any of the above; must be thermal-cycle commissioning | As above | Extended | As above + UFH cost |
Sand-and-Cement Screed
The traditional and most widely used type in the UK, mixed at approximately 1:3 to 1:4.5 cement to sharp sand.2 It is placed as a semi-dry mix (sometimes described as a “paving consistency” or “floor screed consistency”) and tamped or floated level. Minimal equipment needed, wide contractor base, and easily repaired. The main drawback is its long natural drying time: allow about one day per millimetre of thickness for the first 50 mm, and progressively longer for each millimetre beyond that.3
Liquid Calcium Sulphate Screed (Anhydrite)
Increasingly common in UK construction, anhydrite screed is pumped as a free-flowing liquid and self-compacts. It is particularly well-suited to underfloor heating because it flows around the pipes without leaving voids, generally conducts heat better than sand-and-cement, and can be laid thinner: a floating calcium sulphate screed can be as little as 35 mm thick, against 65 mm or more for a traditional floating screed, reducing floor build-up.2 Key disadvantages: it needs good ventilation and often drying aids before most floor coverings can be applied, and it is generally not suitable where it could get damp or wet.2
Self-Levelling Compound
Not a structural screed but a thin repair or levelling product poured over an existing sub-floor to fill low spots and create a smooth, flat surface. Useful for renovations where the existing floor is serviceable but uneven. Not suitable as a standalone screed over new construction.
Screed Depths and Building Regulations
In England and Wales, Part C of the Building Regulations (Site preparation and resistance to contaminants and moisture) requires that ground floors are protected from moisture. A damp-proof membrane (DPM), typically 1200-gauge polythene laid over the slab, should be incorporated.4 Screed is laid over the DPM and insulation.
Minimum screed depths:
- Bonded screed (directly onto concrete, no membrane): minimum 25 mm, typically 25–40 mm2
- Unbonded screed (over a DPM): minimum 50 mm, with at least 70 mm usually specified to allow for level tolerances2
- Floating screed (over insulation): minimum 65 mm for lightly loaded floors, 75 mm for heavily loaded ones5
- Floating screed over UFH (anhydrite): minimum 30 mm cover over the pipes2
- Floating screed over UFH (sand-and-cement): minimum 25 mm over pipes and 75 mm overall5
When underfloor heating is incorporated, the screed must be commissioned (heated progressively from cold to operating temperature and back) before floor coverings are laid. This process typically takes two to three weeks.
Screed Drying Times
This is the most frequently misunderstood aspect of screed. Applying floor coverings, particularly moisture-sensitive materials such as engineered timber, solid wood, or adhesive-fixed tiles, before the screed has dried to the required moisture content causes significant damage: timber swells and cups, adhesives fail, tiles debond.
| Screed Type | Rule of Thumb | Typical Wait (65 mm) |
|---|---|---|
| Sand-and-cement | 1 day per mm for the first 50 mm, longer beyond | 65+ days |
| Anhydrite liquid | 1 day per mm + drying aids | 45–75 days (with dehumidification) |
| Rapid-drying | 1 day per 1.5 mm | 40–45 days |
| Heated rapidly (specialised) | Per manufacturer’s specification | 10–28 days |
Required moisture content before laying:
- Most floor coverings: ≤75% relative humidity measured in situ (using a hygrometer probe or Tramex meter)3
- Moisture-sensitive wood flooring: ≤65% RH
- Adhesive-critical applications: check adhesive manufacturer specification
Dehumidification, forced ventilation and underfloor heating commissioning all accelerate screed drying but do not eliminate the requirement for moisture testing before flooring.
Underfloor Heating and Screed
UFH is typically embedded in screed rather than below it to maximise heat transfer to the room above. Pipe centres are typically 100–200 mm for water-fed systems. The screed acts as a thermal store and radiator.
Key specification points:
- Anhydrite screed: generally conducts heat better than sand-and-cement, and makers declare their own values, for example 2.5 W/mK for Tarmac’s Topflow Screed A6
- Sand-and-cement screed: lower conductivity than most liquid screeds, so use the declared or design value in the heating calculation
- Always commission the UFH system before laying finished floor covering
Cost Summary (2026)
| Scope | Typical Cost |
|---|---|
| Traditional screed, average room (25 m²) | £375–£550 |
| Liquid screed, average room (25 m²) | £450–£850 |
| Rapid-drying screed, average room | £700–£1,125 |
| Self-levelling compound, average room | £300–£625 |
| Full ground floor, 4-bed house (80 m²) | £1,200–£3,600 |
| UFH installation before screeding | £60–£120/m² additional |
Materials represent roughly 40–60% of the installed cost; specialist pumped liquid screeds carry a higher proportion of materials cost.
Choosing a Screeding Contractor
Not all general builders have experience with liquid anhydrite screeds. For pumped screeds, look for contractors using equipment supplied by manufacturers such as Gypsol, Cemfloor or Tarmac. Ask for evidence of moisture testing on previous projects before floor coverings were laid, this is the clearest indicator of a contractor who understands the critical interface between screeding and flooring.
References (6)
Figures in this note were checked against the sources below on 30 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.
- 1costsupplier figureMidland Screed Floor.RN-8AU4X6A price, true at 2026-06. A Midlands liquid screed contractor's 2026 price guide, with per square metre rates for domestic and commercial installations. Useful alongside the London figures as a second published rate from a different region, which is a cleaner way to show regional variation than applying a multiplier.
- 2technicalgoodThe Concrete Centre (Mineral Products Association), guidance.RN-H7BYXYThe Concrete Centre on floor screeds: the traditional 1:3 to 1:4.5 cement to sharp sand mix, minimum thicknesses for bonded, unbonded and floating screeds, and the difference between laying onto an in-situ slab and onto precast units. This is the source for the thickness a screed has to be, which is the number that decides whether a floor build-up fits under a door.
- 3technicalvery strongLABC Warranty, guidance.RN-AHXL1OSection 4 of the LABC Warranty Technical Manual version 10, on ground floors: suspended beam and block, ground supported slab, suspended slab, general requirements for concrete floors, and suspended timber. A structural warranty provider's requirements, which are usually tighter than the Building Regulations minimum because the provider is carrying the risk for ten years. Useful as the practical specification for each floor type.
- 4technicalvery strongMinistry of Housing, Communities and Local Government.RN-NPO8FJThe statutory figures behind a damp diagnosis, and the numbers to quote when a note explains why ground levels or a bridged damp proof course cause rising damp. Paragraph 5.2 requires that in an external wall the damp-proof course should be at least 150mm above the level of the adjoining ground (Diagram 8) unless part of the building protects the wall, and that in an external cavity wall the cavity should be taken down at least 225mm below the level of the lowest damp-proof course, or a damp-proof tray provided (Diagram 9a). For suspended timber ground floors it requires a ventilated air space of at least 75mm from the ground covering to the underside of any wall-plates and at least 150mm to the underside of the suspended timber floor or insulation, with ventilation openings on two opposing external walls of not less than 1,500mm2 per metre run of external wall or 500mm2 per square metre of floor area, whichever is greater; for suspended concrete floors the clear ventilated space is at least 150mm with the same opening sizes. Section 2.39 onwards covers radon, referring to BRE Report BR 211 for protective measures. The 2013 edition was published on 3 September 2013 with changes in effect from 1 October 2013.
- 5technicalgoodThe Concrete Centre (Mineral Products Association), guidance.RN-06S45EThe Concrete Centre's comparison table of screed materials: traditional cement-sand, modified cement-sand, cementitious self-smoothing and calcium sulfate self-smoothing, each with its advantages, drying behaviour and build-up. This is the table that answers why an anhydrite screed can go down thinner and in larger bays than a sand and cement one, and why it then has to be sanded before a floor finish.
- 6technicalsupplier figureTarmac, guidance.RN-Z83W9HTarmac's product page for its calcium sulphate liquid screed. It states the daily output a pumped liquid screed can achieve, up to 1,200 square metres.
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Liquid Screed Cost UK | 2026 Price Guide per m2, Midland Screed Floor, accessed 30 September 2026. Priced at 2026-06, so no calibration is needed. midlandscreedfloor.co.uk
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Floor screeds, The Concrete Centre (Mineral Products Association), accessed 7 September 2026. concretecentre.com
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Technical Manual Version 10, Section 4: Ground floors, LABC Warranty, accessed 7 September 2026. labcwarranty.co.uk
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Approved Document C: Site preparation and resistance to contaminants and moisture, 2004 edition incorporating 2010 and 2013 amendments, HM Government (GOV.UK), accessed 7 September 2026. assets.publishing.service.gov.uk
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Screed specification: Table 1, comparison of screed materials and types of screed build-up, The Concrete Centre (Mineral Products Association), accessed 7 September 2026. concretecentre.com
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Topflow Screed A, Tarmac, accessed 30 September 2026. tarmac.com
