Guides · checked 29 October 2026
Preparing a site for screeding
What has to be in place before the screeding crew arrives, from the makers' installation guides.
- Free quote request
- One contractor rings you
- Sources under every figure
Figures checked against each source on 29 October 2026. How we check
A screed can only be as good as what's under it and the conditions it goes down in. The building should be closed in, the base and membranes in place, the insulation flat, the edge strip round every wall, and any heating pipes fixed and pressure tested.
Roadstone wants the inside air between 5°C and 20°C for FlowPlus. Gyvlon wants underfloor heating pipe clipped at least every 400 mm and pressure tested, preferably with water.
The checklist
- Close the building in.Roof on, windows and doors in or sealed with polythene, insulation or ply (Gyvlon). Roadstone says the building should be weatherproof before screeding.
- Damp-proof and radon membranes.On a ground floor there must be a damp-proof membrane below the screed or sub-base (Roadstone). In High Radon Areas a radon membrane has been required since 1 July 1998, and every building since then needs a standby radon sump (EPA).
- Base ready.For a bonded screed, the slab prepared mechanically for bond (MPA). For floating, insulation boards flat on the base with no rocking (Gyvlon).
- Polythene over the insulation.At least 500 gauge, lapped 100 mm and taped, sealed to the edge strip's skirt. Never the foil tape that comes with the boards (Gyvlon).
- Edge strip round every wall.At least 8 mm, 10 mm with underfloor heating, pushed into corners without stretching (Gyvlon). Round columns too (Roadstone).
- Heating pipes fixed and tested.Clipped or stapled at least every 400 mm and pressure tested, preferably with water, before screeding (Gyvlon).
- Joint formers.Where the bays split, between separately controlled heating circuits, at thresholds and over structural joints (Roadstone, Gyvlon).
- Temperature.Inside air between 5°C and 20°C for FlowPlus (Roadstone). Mapei gives +5°C to +35°C for Topcem.
Sources: Gyvlon flowing screed general data pack (Anhydritec); Roadstone FlowPlus cement liquid screed brochure (RS.BRO-19 Rev 01, March 2022); EPA, Radon advice for builders; Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023); Mapei Topcem technical data sheet. Checked 29 October 2026.
- Polythene Lapped 100 mm and taped.
- Insulation Flat and firm.
- Damp-proof and radon membrane Where required.
- Slab
- Hardcore
On the day
- Access for the truck and pump, and a clear run for the hose to each room.
- Water and power on site, if the contractor needs them. Ask.
- Everyone else kept off the floor until it can take foot traffic: 24–48 hours for liquid screeds (Roadstone, Cemfloor, Gyvlon).
- Windows and doors kept closed: 7 days for FlowPlus (Roadstone), the first 48–72 hours for Gyvlon.
Sources: Roadstone FlowPlus cement liquid screed brochure (RS.BRO-19 Rev 01, March 2022); Cemfloor Complete technical data sheet (2023); Gyvlon flowing screed general data pack (Anhydritec). Checked 29 October 2026.
After the pour
- Sand and cement: covered with polythene for at least 5 days (MPA).
- Then warmth and ventilation, without draughts tunnelling through (Roadstone).
- The heating brought up on the maker's schedule before any floor finish.
- The screed tested before the floor finish goes down.
Sources: Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023); Roadstone FlowPlus cement liquid screed brochure (RS.BRO-19 Rev 01, March 2022). Checked 29 October 2026.
Questions people ask
What needs to be done before screeding?
Building closed in, membranes and insulation down, polythene lapped and taped, edge strip round every wall, and any heating pipes clipped and pressure tested.
Does the house need to be weathertight for screeding?
Yes. Roadstone says the building should be weatherproof before FlowPlus goes down, and Gyvlon wants the roof on and openings sealed.
What temperature is needed for screeding?
Roadstone gives 5°C to 20°C inside for FlowPlus. Mapei gives +5°C to +35°C for Topcem.
Do underfloor heating pipes need testing before screeding?
Yes. Gyvlon says the pipework must be pressure tested, preferably with water, before the screed goes in.
Sources (5)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Gyvlon flowing screed general data pack (Anhydritec): specifiedby.com
- Roadstone FlowPlus cement liquid screed brochure: roadstone.ie
- Mineral Products Association, Mortar Data Sheet 22: Screeds: mortar.org.uk
- Mapei Topcem technical data sheet: cdn.shopify.com
- Cemfloor Complete technical data sheet: cdn.shopify.com
Get your floor priced
Four taps about the job and one screeding contractor who covers your county rings you. Or call 087 162 1846, lines open 8am to 8pm.