A screed (mortar bed) levels the slab before tile, vinyl or laminate. Its volume is the area times the thickness; the mix ratio says how much of it is cement and how much is sand.
The calculator gives both options: mixing cement and sand on site, and buying bagged ready-mix screed.
How to use
- Enter the floor area.
- Type the average thickness. Measure the low and high points if the slab isn't level.
- Choose the mix: 1:3 is stronger, 1:4 is the usual floor screed, 1:5 for thick fills.
- Read the cement, sand and ready-mix bags.
Cement and sand per cu yd of screed
| Mix | Cement per cu yd | 94 lb bags per cu yd | Sand per cu yd | Cement for 100 sq ft × 2 in |
|---|---|---|---|---|
| 1:3 | 950 lb | 10.1 | 1.25 cu yd | 586 lb |
| 1:4 | 777 lb | 8.3 | 1.37 cu yd | 480 lb |
| 1:5 | 642 lb | 6.8 | 1.41 cu yd | 396 lb |
From the Brazilian SINAPI cost tables (cement:sand by volume, damp sand). Without waste.
How thick should a screed be?
Bonded to the slab: from about 3/4 in (2 cm). Unbonded or floating over insulation: at least 1 3/4 to 2 in (4.5 to 5 cm). Very thin layers crack; for less than 3/4 in, use a self-leveling underlayment instead.
Ready-mix bags
Bagged screed weighs about 20 kg per m² for each cm of thickness (Würth and Baumit data sheets), roughly 4 lb per sq ft per inch. An 80 lb bag covers about 3.8 sq ft at 2 in.
Where the numbers come from
Coverage and consumption figures come from manufacturer data sheets and published standards: