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 floor preparation, whether for residential, commercial, or industrial projects. Screed provides a smooth, level surface for final floor finishes such as tiles, carpet, or vinyl, and ensures proper structural integrity. For most UK projects, you'll choose between traditional cement screed or modern anhydrite (calcium sulphate) screed, each with distinct laying methods, drying times, and cost implications. The typical project costs between £25-50 per square metre including materials and labour, with completion usually taking 1-2 days for the laying process itself, though drying times vary significantly.
The equipment you need depends entirely on your project scale and screed type. For small residential rooms under 20m², manual mixing and hand laying tools suffice. Mid-sized projects (20-100m²) benefit from forced-action mixers and screed pumps, while large commercial floors over 100m² typically require dedicated screed pumps with boom systems or laser-guided screeding machines. Anhydrite screed is almost always pumped and requires specialist contractors with certified equipment, whereas traditional sand-cement screed offers more flexibility for DIY or smaller contractors. Understanding which approach suits your project scope, timeline, and budget is essential before committing to materials or hiring equipment.
Step-by-step
1. Surface preparation and priming
Thoroughly clean the substrate, removing all dust, debris, oil, and loose material. Check for structural cracks or damp issues that require remediation first. Install damp-proof membranes (DPM) if working on ground-bearing slabs, ensuring 150mm overlaps and runs up walls. Apply appropriate primer to the substrate—bonding agents for bonded screeds or separation layers for unbonded screeds. Install edge insulation strips around the perimeter to allow for thermal expansion. This preparation stage is critical and poor execution here causes most screed failures including delamination and cracking.
2. Install level datum points and screeding guides
Establish the finished floor level using a laser level or optical level, marking clearly on walls. Install screed rails or timber battens at regular intervals (typically 1.2-1.5m apart) set to the exact finished level, accounting for screed thickness. For bonded screeds, minimum 25mm thickness is required; for unbonded screeds, minimum 50mm; and for floating screeds over insulation, minimum 65-75mm. Secure the guides firmly as they'll be used to strike off the screed. Professional contractors using laser screeding systems may skip physical rails, instead using laser receivers on the screeding machine itself.
3. Mix and transport screed material
For cement screed, use a 4:1 or 3:1 sand-to-cement ratio (sharp sand, not building sand) mixed in a forced-action mixer—never a standard drum mixer which won't achieve adequate consistency. Mix to a relatively dry, crumbly consistency that holds together when squeezed. For anhydrite screed, specialist contractors will pump pre-mixed liquid screed from a silo truck through hoses directly to the pour location. Cement screed must be transported quickly via wheelbarrows or conveyor systems and used within 2 hours of mixing. Plan your mixing location to minimise transport distance, and have adequate labour for continuous supply to maintain workflow.
4. Lay and compact the screed
Pour mixed screed between the guide rails, slightly overfilling. Use a straight edge or beam screed to strike off excess material, moving in a sawing motion while advancing forward to achieve a level surface flush with the rails. Immediately compact the screed using tamping beams or poker vibrators to eliminate air pockets and ensure density—inadequate compaction leads to weak, friable surfaces. For large areas, work systematically in bays to maintain quality control. Anhydrite screed is self-levelling once pumped and requires minimal finishing, just light smoothing with a dappling bar to release trapped air and ensure consistent surface level.
5. Finish and protect the surface
Once initial set begins (usually 30-60 minutes for cement screed), remove guide rails if temporary and fill voids with fresh material. Use a wooden or magnesium float to work the surface to the required finish—smoother for tile adhesives, textured for mechanical keys. Avoid overworking which brings laitance to the surface. Protect the fresh screed from rapid drying, foot traffic, and frost. Cover cement screed with polythene sheets after initial set to retain moisture for proper curing. Maintain ambient temperature above 5°C and prevent draughts. Mark access routes clearly and restrict access for at least 24-48 hours for foot traffic, longer for wheeled loads.
6. Curing and drying
Traditional cement screed requires at least 7 days moist curing for strength development—keep covered and periodically dampen if necessary in warm conditions. Full drying takes approximately 1 day per mm thickness up to 50mm (so 50 days for 50mm screed), then longer for additional depth. Anhydrite screed typically allows foot traffic after 24-48 hours and dries faster, approximately 1 day per mm for the first 40mm. Before laying impermeable floor finishes, conduct moisture testing using hygrometers or calcium carbide tests to ensure moisture content is below 75% RH for cement screed or below manufacturer specifications for anhydrite. Premature covering causes failures including adhesive breakdown and floor lifting.
Cost breakdown
| Cement screed materials (sand, cement) | £8-15/m² | For 50-75mm thickness, varies by supplier and volume discounts |
|---|---|---|
| Anhydrite liquid screed materials | £18-28/m² | Includes delivery in silo truck, minimum order quantities typically 5m³ |
| Forced-action mixer hire | £60-120/day | Essential for cement screed quality, drum mixers inadequate |
| Screed pump rental (if required) | £150-300/day | For larger cement screed projects, includes operator training |
| Labour costs (professional contractors) | £12-22/m² | Experienced screed layers, varies by region and project complexity |
| DPM, insulation, edge strips | £3-8/m² | Essential ancillary materials, depends on specification |
| Equipment and consumables (floats, rails, protective sheeting) | £50-150 total | One-off or minimal costs for typical domestic project |
Common pitfalls
- Inadequate substrate preparation—screed delaminates within months, requiring complete removal and re-laying costing £40-60/m²
- Insufficient screed thickness for unbonded or floating systems—cracking occurs under load, typically requiring £35-50/m² repair or replacement
- Laying screed in freezing conditions below 5°C—frost damage causes surface breakdown and loss of strength, necessitating grinding or overlay at £25-40/m²
- Covering floor finishes before screed is fully dry—trapped moisture causes adhesive failure, tile lifting, and potential mould growth requiring £30-55/m² remediation
- Using incorrect sand-cement ratios or poor mixing—weak, dusty screed surface requires expensive resin hardeners or complete replacement
- Failing to install movement joints in large bays—uncontrolled cracking develops, requiring cutting and filling joints retroactively at £8-15 per linear metre
FAQ
- Do I need Building Regulations approval or permits to lay screed in the UK?
- For most screed replacement or new screed in existing buildings, you don't need separate Building Regulations approval specifically for the screed itself. However, if the work is part of a larger project (such as an extension, loft conversion, or significant renovation), the overall project will require Building Control approval, and your screed specification must comply with relevant standards including thermal insulation U-values and sound transmission requirements in Part L and Part E respectively. For ground-bearing floors, compliance with damp-proofing requirements is essential. Always inform Building Control of your floor construction methods during the approval process. Listed buildings may have additional conservation requirements.
- What's the realistic cost difference between DIY screed laying and hiring professionals?
- DIY cement screed for a typical 30m² room costs approximately £240-450 for materials plus £150-250 for equipment hire (mixer, rails, tools), totalling around £390-700 or £13-23/m². Professional installation for the same area costs £750-1,500 (£25-50/m²) including all materials and labour. The £350-800 premium buys you guaranteed quality, proper mixing and compaction, appropriate thickness, faster completion, and crucially, comeback rights if problems emerge. For anhydride screed, DIY isn't realistic—it requires specialist pumping equipment and certified installation, so professional costs of £25-35/m² are unavoidable. First-time DIY screed layers commonly make costly errors in levels, mixing ratios, or curing that require expensive remediation, often negating initial savings.
- Should I choose cement screed or anhydrite liquid screed for my project?
- Cement screed suits smaller projects under 50m², renovation work, and situations requiring traditional methods or minimal drying time constraints. It's more forgiving for DIY, allows localised repairs, and works in varied temperatures. However, it requires 1mm/day drying time, heavy manual labour, and careful mixing. Anhydrite liquid screed is superior for larger areas over 75m², underfloor heating systems (better thermal conductivity), and projects requiring rapid installation with guaranteed flatness. It's pumped quickly, self-levels, and dries faster (1mm/day up to 40mm). Disadvantages include higher material costs, minimum order quantities (typically 5-8m³), requirement for specialist contractors, and sensitivity to moisture before sealing. For underfloor heating, anhydrite is generally preferred by installers due to improved heat transfer and reduced thickness requirements.
- How long must I really wait before laying tiles or vinyl on new screed?
- This depends critically on screed type and floor covering. For tiles with flexible adhesive on cement screed, wait minimum 3-4 weeks (or 1 day per mm up to test moisture levels). Moisture content must be below 75% RH measured with a hygrometer. For impermeable vinyl or LVT, cement screed must reach below 75% RH throughout its full depth, taking 6-8 weeks for 50mm screed in good drying conditions, potentially much longer in cold or humid environments. Anhydrite screed typically allows tiling after 5-7 days for foot traffic areas, but still requires moisture testing before impermeable coverings—usually 3-4 weeks for domestic projects. Premature covering is the single most common cause of floor failures. Always conduct calcium carbide or electronic moisture testing before proceeding; hiring a moisture meter costs £30-50 and prevents thousands in remediation costs. Never rely solely on surface dryness or elapsed time.
- What equipment do I actually need for a 40m² residential room screed project?
- Essential equipment includes: a forced-action mixer (£80-120/day hire—never use a standard cement mixer as it won't properly blend screed), wheelbarrows for transport (2-3 for continuous workflow), screed rails or timber battens for level guides, a long straight edge or beam screed (2-3m length), a laser level or optical level for establishing datum, hand tamps or tamping beam for compaction, wooden or magnesium floats for finishing, buckets and shovels, protective polythene sheeting, and edge insulation strips. For this size, manual laying is feasible but physically demanding—budget 2-3 labourers for efficient workflow. A small site mixer for larger batches may be cost-effective versus multiple forced-action mixer loads. You'll also need PPE: gloves, knee pads, and dust masks. Total equipment hire for a weekend project: £150-250. If considering screed pump hire (£200-300/day), the project scale needs to exceed 60-80m² to justify costs versus manual methods.
- Can I lay screed in sections over multiple days for a large area?
- Yes, but you must create proper construction joints between pours to manage this correctly. Each section or 'bay' should be a complete area bounded by walls or purposely installed joint formers. Stop each day's work at a straight edge, cutting back to sound material, then treat the joint edge with bonding agent before continuing the next day—this creates a deliberate construction joint rather than a cold joint that will crack. Maximum bay sizes are typically 40m² for bonded screed, 30m² for unbonded. Always plan your bay layout before starting to ensure logical workflow and joint placement in low-traffic areas where possible. For large floors, also install movement joints at doorways and where different floor areas meet, using compressible foam strip before screeding. Professional contractors often complete large areas in a single continuous pour to avoid joints, which is why gang sizes of 4-6 workers are common on commercial projects. Poor joint execution is a primary cause of cracking in phased screed projects.