Floor Screed Material Calculator
Floor Screed Material Calculator
Need to mix your own floor screed? This tool helps calculate the exact amount of cement, sand, and optional additives you'll need based on the volume of screed required. Works for both traditional and fibre-reinforced screeds in the UK or USA.
Technical Guidance
- UK: Traditional screed mix is 1:4 or 1:3 cement to sharp sand
- USA: Use PSI-rated cement (e.g. 3000 psi) — often mixed 1:4 or 1:5 by volume
- One cubic metre = approx. 2.2 tonnes of material (dry volume)
- Allow 10% extra material for waste, spillage, or uneven substrate
Material Quantities Per Cubic Metre
| Mix Ratio | Cement (bags) | Sand (kg) | Total Weight |
|---|---|---|---|
| 1:4 | 12 x 25kg | 1600 kg | 1.9–2.0 tonnes |
| 1:3 | 16 x 25kg | 1500 kg | 2.1–2.2 tonnes |
| 1:4 + fibres | 12 bags + 1 fibre pack | 1600 kg | ~2.1 tonnes |
Pro Tips
- Use sharp sand, not soft or building sand, for screed mixes
- Pre-mix dry ingredients before adding water for better consistency
- Fibre additives improve crack resistance in large pours
Common Mistakes
- Forgetting to convert from m² × depth to cubic metres
- Using soft sand — leads to weak screed
- Ordering cement in tonnes instead of bags
FAQs
- How many bags of cement per m³ screed? → 12–16 bags (25kg) depending on mix ratio
- Can I use premixed screed? → Yes, just multiply required volume by supplier’s coverage rate
- What about underfloor heating? → Use flowing screed or increase thickness to 65–75mm
Related Tools
Floor Screed – What You Need to Know Before You Order
Floor screed is the unsung hero of smooth, level floors. Whether you're laying tiles, vinyl, laminate or polished concrete — a good quality screed base is essential for durability, insulation, and a crack-free finish.
This calculator helps you estimate materials for traditional site-mixed screed using a standard 1:4 cement-to-sand ratio, but here’s the technical background every builder (or DIYer) should know before diving into a screed project.
🧪 Composition & Types of Screed
Most traditional screed is made from:
- Cement – OPC (Ordinary Portland Cement)
- Sharp Sand – Washed and graded
- Water – Just enough to hydrate the mix
- Optional Additives – Plasticisers, fibres, or retarders
Common types of screed include:
- Unbonded Screed (laid over membrane)
- Bonded Screed (direct to concrete)
- Floating Screed (laid over insulation)
- Fibre-reinforced Screed (for added crack resistance)
- Flowing / Liquid Screeds (anhydrite or gypsum-based – not calculated here)
📏 Minimum Thickness Guidelines (UK & US Standards)
| Application | Minimum Thickness | Notes |
|---|---|---|
| Bonded Screed | 25–40mm | For small residential or refurbishment |
| Unbonded Screed (on DPM) | 50mm | Minimum to prevent shrinkage cracking |
| Floating Screed (insulation layer) | 65–75mm | Add 10mm extra for underfloor heating |
| Heavy Load Areas | 75mm+ | May require reinforcement |
📐 Bulk Density & Material Weight
Material densities used in calculations:
- Cement: 1700 kg/m³
- Sand: 1270 kg/m³
- Screed (dry mixed): ~2130–2200 kg/m³
This helps when ordering materials or arranging transport/skips.
💡 Plasticiser & Additives
Plasticisers reduce water content while improving workability. Benefits include:
- Higher compressive strength
- Reduced shrinkage
- Better bonding
Recommended dosage: approx 0.3 litres per 50kg of cement (included in calculator output).
📊 Compressive Strength Targets
According to BS EN 13813, typical strength classes include:
- C20-F4 – General domestic use
- C25-F5 – Heavy traffic or garage floors
- C30-F6 – Industrial or commercial flooring
Achieving these depends on correct mix, compaction, and curing (moist cure for at least 7 days).
🧯 Fire, Moisture, and Sound Considerations
- Screed is non-combustible
- Use DPM below unbonded screed to block rising moisture
- Consider acoustic layers for flats or upper floors
🔄 Metric & Imperial Conversion
| Measurement | Metric (UK/EU) | Imperial (US) |
|---|---|---|
| Length | Metres (m) | Feet (ft) |
| Depth | Millimetres (mm) | Inches (in) |
| Cement Bags | 25kg / 40kg | 50lb / 94lb |
🧱 Final Thought
A floor is only as good as the screed beneath it. Take the time to calculate your quantities, plan for waste, and choose the right type of screed for the job. You’ll thank yourself later when your tiles don’t crack, your vinyl sits flush, and your floors stand the test of time.
