Having Screed Laid or Laying It Yourself — Which Machine, Which Providers?
- Recommended class
- Zement-/Anhydrit-Estrich
- Typical duration
- 1-2 Tage
- Cost estimate
- 25-50 €/m²
Overview
Laying screed is a critical stage in any construction or renovation project, providing a smooth, level base for final floor finishes such as tiles, carpet, or timber. Whether you're working with traditional cement screed or modern anhydrite (calcium sulphate) screed, the choice between DIY installation and professional contractors depends on project scale, substrate condition, and required tolerances. For small domestic projects under 30m², manual application or compact screeding equipment may suffice, whilst commercial jobs and areas exceeding 100m² typically demand truck-mounted pumps and laser-guided screeding machines to achieve consistent thickness and flatness.
The two dominant screed types—cement-based (sand and cement) and anhydrite (liquid flowing screed)—each require different equipment and expertise. Cement screed can be mixed on-site with a forced-action mixer and laid using straightedges and screeding bars, making it accessible for skilled DIYers. Anhydrite screed, however, arrives ready-mixed in specialist tankers and is pumped into place, offering superior flatness and faster drying but necessitating professional installation. Typical project duration ranges from one to two days for curing to walking strength, though full cure takes significantly longer. Costs generally fall between £25–50/m² including materials and labour, with DIY projects saving on labour but requiring equipment hire and careful execution to avoid costly remedial works.
Step-by-step
1. Substrate Preparation and Assessment
Inspect the base slab or subfloor for cleanliness, structural integrity, and level variations. Remove all debris, dust, oil, and loose material using industrial vacuum cleaners or sweeping compounds. Repair cracks wider than 3mm with appropriate repair mortar. Check for damp using a moisture meter—readings above 75% relative humidity require remedial damp-proofing. Install damp-proof membrane (DPM) if not integral to the slab, overlapping joints by minimum 150mm and turning up at walls. Mark screed finished floor level (FFL) on walls using a laser level or water level, accounting for screed thickness (typically 65–75mm bonded, 50mm unbonded, or 35mm floating).
2. Installation of Insulation and Edge Strips
For floating screeds, lay rigid insulation boards (polyurethane, PIR, or EPS depending on thermal and load requirements) tightly together without gaps. Tape joints with aluminium foil tape to prevent screed penetration. Install compressible edge strips around all perimeters, columns, and penetrations to allow thermal expansion—typically 10mm thick closed-cell polyethylene foam. These movement joints are critical to prevent cracking and curling. For underfloor heating installations, clip pipework securely to the insulation using proprietary fixings at 300mm centres, pressure-test the system to 6 bar, and leave pressurised during screeding.
3. Priming and Batching (Cement Screed) or Delivery Coordination (Anhydrite)
For bonded cement screeds, apply a slurry bond coat of 3:1 sharp sand to cement mixed with water to a creamy consistency, brushing vigorously into the substrate immediately before screeding. For unbonded screeds, lay polyethylene separating membrane with 150mm overlaps. Batch cement screed using a forced-action mixer at typical ratios of 1:4 cement to sharp sand (or use factory-bagged screed mix). For anhydrite screed, coordinate delivery timing with the supplier—pumping trucks require access within 3 metres of pour areas and level hardstanding. Plan pour sequence to avoid trapped areas and ensure continuous workflow.
4. Laying and Levelling the Screed
For cement screed, establish screed rails or dot-and-dab levelling spots at maximum 2-metre centres using the same screed mix, set precisely to FFL marks. Tip screed between rails and compact thoroughly using a tamping beam or mechanical compactor to eliminate voids, working backwards from the far corner. Strike off excess using a straightedge in a sawing motion. For anhydrite screed, the pump operator controls flow whilst operatives use simple rakes to guide material into corners—the self-levelling properties minimise manual effort. Use a dappling bar or spiked roller to release trapped air bubbles. Maintain room temperature above 5°C and ensure adequate ventilation.
5. Surface Finishing and Initial Curing
For cement screeds, allow initial set (45–90 minutes depending on conditions) then finish with a wooden or magnesium float to close the surface. Avoid over-trowelling which brings laitance to the surface. For power-floated finishes, use a helicopter trowel once the screed bears foot pressure with minimal indentation. Cover cement screed with polythene sheeting after 4–6 hours to prevent rapid moisture loss and microcracking. Anhydrite screeds require no surface finishing beyond the spiked roller treatment. Protect all screeds from traffic, direct sunlight, and draughts for minimum 24–48 hours.
6. Curing, Drying, and Handover
Cement screed reaches walking strength in 24–48 hours but requires 7 days minimum before light trafficking and 28 days for full structural cure. Moisture content must drop below 75% RH (for cement) or specified levels for anhydrite (typically 0.5% CM for tiles, 0.3% for impermeable finishes) before applying floor coverings—this may take 1 day per mm of thickness in good drying conditions. Use calibrated hygrometers or carbide meters to verify. For underfloor heating, follow a controlled commissioning schedule, gradually increasing temperature over several days. Remove edge strips where they protrude above finished floor level and seal expansion joints appropriately for the chosen floor finish.
Cost breakdown
| Cement screed material (25kg bags or bulk) | £8–15/m² | Factory-mixed bags more expensive but consistent; bulk sand/cement cheaper for large areas |
|---|---|---|
| Anhydrite liquid screed (supplied and pumped) | £18–28/m² | Includes delivery, pumping, and material; minimum order quantities typically 5–8m³ |
| Insulation boards (100mm PIR or equivalent) | £12–20/m² | Varies by thermal performance and compressive strength rating required |
| DPM, edge strips, tapes, and sundries | £3–6/m² | Includes 1200-gauge polythene, 10mm edge foam, and fixing/jointing materials |
| Equipment hire (mixer, laser level, floats, etc.) | £80–180/day | Forced-action mixer £60–100/day; rotating laser £40–80/day; spiked roller £20–30/day |
| Labour for professional installation | £12–22/m² | Typically 2-person gang laying 100–200m²/day depending on complexity and screed type |
| Underfloor heating pipework and manifold | £18–35/m² | If applicable; includes pipe, manifold, controls, and installation by specialist subcontractor |
Common pitfalls
- Insufficient substrate preparation—laying screed over dusty or contaminated surfaces causes debonding, resulting in hollow-sounding drums and potential failure requiring £30–50/m² removal and replacement.
- Omitting edge expansion strips—thermal and moisture movement causes perimeter cracking and curling, particularly noticeable with large floor areas and underfloor heating, necessitating expensive crack injection repairs.
- Inadequate screed thickness—floating screeds thinner than 35mm or bonded screeds under 25mm lack structural integrity and crack extensively, requiring complete removal at £25–40/m² plus re-screeding costs.
- Premature floor covering installation—laying impermeable finishes before screed dries traps moisture causing adhesive failure, tile debonding, and vinyl bubbling; remediation costs £40–80/m² including finishes replacement.
- Poor batching consistency in cement screed—varying water content between mixes creates differential shrinkage and surface level variations exceeding tolerances, requiring costly grinding or self-levelling overlay at £15–30/m².
- Ignoring ambient conditions—screeding in temperatures below 5°C or in unventilated spaces prolongs curing dramatically and may cause surface dusting or weak strength development requiring surface hardeners or replacement.
FAQ
- Do I need Building Regulations approval or permits for laying screed in the UK?
- Floor screeds themselves don't typically require separate Building Regulations approval, but the overall floor construction must comply with Approved Documents, particularly Part L (thermal insulation) and Part C (moisture resistance) for ground floors. If you're adding screed as part of an extension, loft conversion, or structural alteration requiring Building Control involvement, the screed specification will be reviewed as part of the floor construction detail. For replacement screeds in existing buildings without structural changes, notification isn't usually necessary, but any new damp-proof membranes or insulation must meet current standards. Always verify with your local authority Building Control department for projects involving structural floors or where the property use is changing.
- What's the realistic cost difference between DIY screeding and hiring professionals?
- For a typical 50m² domestic project, DIY cement screeding costs approximately £650–1,000 (materials £400–750, equipment hire £150–250, sundries £100) versus £1,850–3,500 for professional installation including materials and labour. The savings of £1,200–2,500 must be weighed against the skill required, physical effort, and risk of costly mistakes—poorly laid screed requiring remedial work can exceed professional costs. Anhydrite screed is rarely viable for DIY as it requires specialist pumping equipment and trained operatives; professional installation costs £1,350–2,100 for the same area but offers superior flatness and faster project completion. For areas exceeding 100m² or requiring tight tolerances (SR2 or better), professional installation becomes increasingly cost-effective due to economies of scale and specialist equipment.
- Should I choose cement screed or anhydrite screed for my project?
- Cement screed suits smaller projects, refurbishments with restricted access, and situations requiring traditional sand/cement systems for compatibility or specification requirements. It's DIY-feasible, readily available, and familiar to most builders, but requires skilled laying for flatness, has higher shrinkage risk, and takes longer to dry (typically 1mm per day). Anhydrite screed excels in new-build projects over 80m², installations with underfloor heating (superior thermal conductivity), and where speed and flatness are priorities—it's pumped rapidly, self-levels to superior tolerances, and can achieve faster drying with forced drying protocols. However, it costs 20–40% more, requires specialist suppliers and applicators, needs surface preparation (light scabbling or priming) before tiling, and demands careful protection from water during curing. For domestic refurbs under 60m², cement screed is usually most practical; for commercial projects and new-builds with UFH, anhydrite offers better performance and overall project speed.
- How long must I wait before installing floor coverings after screeding?
- Waiting times depend critically on screed type, thickness, and drying conditions. Cement screed requires minimum 1 day per mm thickness in good conditions (20°C, 60% RH, adequate ventilation)—so 65mm screed needs approximately 9 weeks to reach 75% RH suitable for most coverings. Forced drying with dehumidifiers can halve this time but shouldn't start until after 7-day initial cure. Anhydrite screed dries faster, often achieving tile-ready moisture (0.5% CM) in 3–5 weeks for 50mm thickness, and can be force-dried from day one. Always verify with calibrated moisture testing—hygrometers (for cement) or carbide meters (for anhydrite)—as laying impermeable coverings over wet screed causes guaranteed failure. Carpet and breathable finishes tolerate higher moisture than vinyl, resin, or sheet materials. For underfloor heating, commission the system progressively after initial cure but before final finishes to drive out residual moisture.
- What thickness of screed do I need for different floor types and loadings?
- Bonded screeds (adhered directly to structural concrete) require minimum 25mm for light domestic use, preferably 40mm for reliability. Unbonded screeds (separated by membrane) need minimum 50mm, ideally 65–75mm to resist curling and cracking. Floating screeds (over insulation) must be minimum 65mm for domestic foot traffic, 75mm for areas with wheeled traffic or point loads. For commercial or industrial loadings, increase to 75–100mm depending on load specifications. These minimums assume proper reinforcement where required—welded steel mesh (A142 or A193) for larger areas or where cracking risk is high. Anhydrite screeds can often be 10mm thinner than cement equivalents due to higher flexural strength. For underfloor heating, pipes should be covered by minimum 30mm screed above the pipe crown, so a 16mm pipe diameter in 65mm total screed provides adequate coverage and thermal response. Always consult structural engineers for heavy loadings, and follow manufacturer specifications for proprietary screed systems.
- Can I lay screed myself with just basic DIY skills or should I hire professionals?
- Laying cement screed is physically demanding and requires good technique to achieve acceptable results—it's feasible for competent DIYers with construction experience but challenging for those with only basic DIY skills. Critical skills include accurate level-setting with laser or optical levels, consistent mixing to correct consistence, thorough compaction without segregation, and proper timing of finishing operations. Small areas (under 20m²) with forgiving floor finishes offer reasonable learning opportunities; larger areas, tight tolerances (within 3mm over 2m), or preparations for sensitive finishes like vinyl warrant professional installation. Anhydrite screed installation is not realistic for DIY—it requires specialist pumping equipment, trained operatives familiar with flow characteristics, and quality assurance protocols. A middle-ground approach involves hiring professionals for the bulk screeding and tackling small ancillary areas yourself, or engaging a professional for one day to demonstrate technique before you continue. For projects where the floor finish cost exceeds £40/m² or where remedial access is difficult, professional screeding is cost-effective insurance against expensive failures.