Cement-based liquid screed
A cement-based liquid screed flows like anhydrite but sets like cement. A typical Irish cement-based liquid screed is strength class CT-C20-F4: 45 mm floating in a house, 60 mm commercial, 25 mm over heating pipes.
It needs no sanding to the same degree, accepts cement adhesives directly and can be used in wet areas, but its bays are smaller and the heating goes on later than on calcium sulphate.
Free, no obligation. One local screeding contractor prices it, not five.
Two products, side by side
| Cement-based liquid screed | Cement-based liquid screed | |
|---|---|---|
| Supplied | Truck-mixed at ready-mix plants | 25 kg and 1,000 kg bags, mixed on site |
| Strength class | CT-C20-F4 | C25, F5 |
| Floating, house | 45 mm in the installation table (50 mm in its benefits list) | 35 mm |
| Floating, commercial | 60 mm | 40 mm |
| Unbonded | 50 mm, no services in it | 30 mm |
| Bonded | Not given | 20 mm |
| Over heating pipes | 25 mm | 25 mm |
| Biggest bay, heated / unheated | 40 m² / 80 m², no side over 8 m | 100 m² / 150 m² |
| Flatness | Easily achieves SR1 (BS 8204) | SR2 minimum |
| Heating on from | Day 14, water no hotter than 45°C | Not given |
| Surface | Lightly abrade to clean off residue and laitance | No laitance; no sanding |
| Density | About 2,100 kg/m³ dry, 2,200 wet | 2,100 to 2,200 kg/m³ fresh |
The rules for cement-based liquid screed
- The building weatherproof before screeding, with a damp-proof membrane below on a ground floor.
- Internal air between 5°C and 20°C when it's laid, and kept above 5°C in cold weather.
- Windows and doors closed for the first 7 days, then opened now and then for draught-free ventilation.
- Bays under 80 m² unheated and 40 m² heated, with joints between separately controlled heating circuits.
- No more than 80 mm thick, or the drying slows.
- Light partitions up to 50 kg/m² can stand on the floating screed where there's no sound requirement.
- Thermally cycled with the heating before any floor finish.
Cement-based liquid screed in bags
Cement-based liquid screed is the same idea for smaller jobs: a 25 kg bag takes 3.4 to 3.8 litres of water, mixed with a paddle, and has about 30 minutes of pot life at 23°C. Bagged, more than 3.8 litres of water a bag causes bleeding, longer drying, a weaker mix and a poor surface. It recommends an approved specialist screeding contractor.
Calcium sulphate or cement?
Ask for both prices if your contractor lays both. Calcium sulphate gives bigger bays, the heating on a week earlier and a thinner floor; cement-based takes cement adhesives without a barrier primer and, in cement-based liquid screed case, wet areas. Anhydrite screed in detail.
Liquid screed poured by the contractor who takes your call
Calls on this site ring JAM Floor Screeding: James Mulhall, based in Portlaoise, 25 years laying floors. Lines open Mon to Sat, 7am to 6pm. These are his jobs.
“JAM were punctual, professional and efficient and did an outstanding job on pouring our new floor as part of a renovation. Very highly recommend!”
“Excellent work, laser level finish, neat and tidy worker, highly recommend.”
“Top class work by james and his crew, highly recommend”
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Questions people ask
What is cement-based liquid screed?
A flowing screed with a cement binder and admixtures. It flows and self-levels like anhydrite but cures like cement.
How thick is cement-based liquid screed?
45 to 50 mm floating in a house, 60 mm commercial, 50 mm unbonded, and 25 mm over heating pipes.
When can the heating go on under cement-based liquid screed?
After 14 days, with the water no hotter than 45°C.
Does cement liquid screed need sanding?
Cement-based liquid screed says its screed forms no laitance and needs no sanding. It's lightly abraded to clean off residue and laitance.
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