Ready Mixed Floor Screed Calculator
Ready Mixed Floor Screed Calculator (UK & USA)
This calculator helps builders, contractors, and DIYers estimate the volume and weight of ready mixed screed needed for any flooring project. Whether you're working on a garage in Glasgow or a basement in Boston, get accurate figures in seconds!
Technical Guidance
- 🇬🇧 UK: Typical screed mix is 1:4–1:5 (cement:sand) with a density of 2100–2200 kg/m³.
- 🇺🇸 USA: Use pre-blended ready-mix screeds or jobsite mixes with ASTM C472 standards.
- Recommended depth: 50mm for domestic, 75mm for commercial or underfloor heating.
Screed Thickness Guide
| Application | Minimum Thickness |
|---|---|
| Domestic Floors | 50 mm |
| Commercial | 75 mm |
| Floating over Insulation | 65 mm |
| Underfloor Heating | 75 mm (min. 30mm above pipes) |
Density & Conversion Table
| Material | Density (kg/m³) | Weight per m³ (tonnes) |
|---|---|---|
| Ready-Mixed Screed | 2200 | 2.2 |
| Dry Sand Screed | 1850 | 1.85 |
Pro Tips
- Order 5–10% extra to account for waste, over-pour, and settlement.
- Plan for curing: avoid rapid drying or draughts during first 48 hours.
- Use insulation and vapour barriers where needed under screed.
Common Mistakes
- Pouring screed too thin or uneven.
- Not allowing enough drying time — usually 1mm/day.
- Skipping bonding agents on existing concrete bases.
FAQs
- How much screed for 20m² at 50mm?
Answer: 1m³ of screed. - Can I walk on screed next day?
No, wait 24–48 hours minimum depending on mix and weather. - Is fibre screed better?
Yes — it reduces cracking and improves cohesion.
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.
