Screed calculator
The volume of screed for a floor, and the cement and sharp sand for a 1:4 sand and cement screed, or the liquid screed to order.
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Worked example
A 20 m² extension floor with a 65 mm sand and cement screed:
1.30 m³ of screed
- Sand and cement 1:4: 19 bags of cement (25 kg) and 2.08 tonnes of sharp sand
- Liquid screed: order about 1.50 m³ (5% extra, rounded up to the next quarter)
How the sum works
Volume = area × depth. For a mixed-on-site 1:4 screed the dry materials bulk down when water goes in, so the calculator allows 1.25 m³ of dry mix per m³ of screed, then splits it one part cement (about 1,440 kg per m³) to four parts sharp sand (about 1.6 tonnes per m³).
Liquid (anhydrite) screed comes ready-mixed by the m³, so the calculator adds 5 percent and rounds up to the next quarter.
Depth
The depth comes from the specification and the screed type: bonded, unbonded or floating screeds need different minimum depths, and so does screed over underfloor heating. Check the maker's or the designer's figure before you order.