Screed types · checked 29 October 2026
Screed for underfloor heating
How deep over the pipes, how big the bays, and how to bring the heating up the first time.
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Figures checked against each source on 29 October 2026. How we check
Screed over underfloor heating covers the pipes and spreads their heat across the floor. The makers set a minimum cover over the pipes, and Roadstone recommends no more than 80 mm in total because deeper screed takes longer to dry.
Roadstone and Gyvlon both give 25 mm as the minimum cover over the pipes for their liquid screeds. A floating sand and cement screed in a house is normally at least 65 mm. The heating then has to be run through a heat-up cycle before any floor finish goes down.
Screed planner
Plan your screed
Put in your floor and the day it's laid. You get the volume, the weight, when it should be dry enough for floor finishes, and when the heating can go on, from the makers' own figures.
Drying times are for good conditions, closed up and ventilated. The floor is tested before finishes go down, not guessed. None of the Irish screeding contractors' sites we checked publish a price per m², so the price comes from your floor.
Depth over the pipes
| Screed | Over the pipes | Total floating depth | Source |
|---|---|---|---|
| Roadstone FlowPlus (cement liquid) | 25 mm | 50 mm, domestic | Roadstone |
| Cemfloor Complete (cement liquid) | 25 mm | 35 mm floating, domestic | Cemfloor |
| Gyvlon (calcium sulphate) | 25 mm min, 30 mm nominal | 35 mm floating, residential | Gyvlon |
| Sand and cement | – | 65 mm in housing; 65–75 mm ideal over heating | MPA; Designing Buildings Wiki |
| Sand and cement with fibres | – | May reduce to 50 mm | Designing Buildings Wiki |
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); Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023); Designing Buildings Wiki, Screed over underfloor heating (last edited 15 September 2020). Checked 29 October 2026.
The depth guide works through these in detail: screed depth for underfloor heating.
Before the screed goes in
- Pipes clipped or stapled at least every 400 mm so they can't float in a liquid screed (Gyvlon).
- Pipes pressure tested before screeding, preferably with water (Gyvlon).
- Edge strip at least 10 mm with underfloor heating (Gyvlon).
- Floor insulation to a U-value of 0.15 W/m²K where a refurbishment adds underfloor heating, against 0.36 without (SEAI, from TGD L).
- Joint formers between separately controlled heating circuits, and between heated and unheated screed (Roadstone, Gyvlon).
Sources: Gyvlon flowing screed general data pack (Anhydritec); SEAI Domestic Technical Standards and Specifications (v4.0, July 2026); Roadstone FlowPlus cement liquid screed brochure (RS.BRO-19 Rev 01, March 2022). Checked 29 October 2026.
Bay sizes over heating
A heated screed moves more, so the bays are smaller than on an unheated floor:
| Screed | Max bay with heating | Without heating |
|---|---|---|
| Roadstone FlowPlus | 40 m² | 80 m² |
| Cemfloor Complete | 100 m² | 150 m² |
| Gyvlon | 300 m², 20 m long, 6:1 | 1,000 m², 40 m long, 8:1 |
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.
The first heat-up
Every screed over heating goes through a controlled heating and cooling cycle before the floor finish, according to the makers and Designing Buildings Wiki. Gyvlon's procedure for its calcium sulphate screed starts as early as day 7:
Source: Gyvlon flowing screed general data pack (Anhydritec). Checked 29 October 2026.
| Screed | Heating on from | Water temperature |
|---|---|---|
| Gyvlon calcium sulphate | 7 days | Up to 5°C a day, max 50°C |
| Roadstone FlowPlus | 14 days | Max 45°C during the heat cycle |
| Mapei Topcem | 4 days | See Mapei's data sheet |
| Sand and cement | About 21 days of drying first | Turned up in steps |
Sources: Gyvlon flowing screed general data pack (Anhydritec); Roadstone FlowPlus cement liquid screed brochure (RS.BRO-19 Rev 01, March 2022); Mapei Topcem technical data sheet; Designing Buildings Wiki, Screed over underfloor heating (last edited 15 September 2020). Checked 29 October 2026.
Floor finishes
SEAI's technical standards note that tiles, engineered wood and stone conduct heat well and let a heat pump run at lower flow temperatures. Whatever the finish, the screed is tested before it goes down: 75% RH for most finishes.
Sources: SEAI Domestic Technical Standards and Specifications (v4.0, July 2026); Ronacrete, Drying of Screeds. Checked 29 October 2026.
Questions people ask
How much screed goes over underfloor heating pipes?
At least 25 mm of cover for Roadstone FlowPlus, Cemfloor and Gyvlon liquid screeds. A floating sand and cement screed in a house is normally at least 65 mm deep in total.
When can I turn on underfloor heating after screeding?
Gyvlon: from 7 days, raising the water temperature by up to 5°C a day. Roadstone FlowPlus: from 14 days, no hotter than 45°C. Sand and cement: Designing Buildings Wiki suggests about 21 days of drying first.
Do the pipes need to be pressure tested before screeding?
Yes. Gyvlon says the pipework must be pressure tested, preferably with water, before the screed goes in.
Why are bays smaller over underfloor heating?
The screed heats and cools and moves more. Roadstone's limit drops from 80 m² to 40 m² with heating, and Gyvlon's from 1,000 m² to 300 m².
Sources (7)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Roadstone FlowPlus cement liquid screed brochure: roadstone.ie
- Cemfloor Complete technical data sheet: cdn.shopify.com
- Gyvlon flowing screed general data pack (Anhydritec): specifiedby.com
- Mineral Products Association, Mortar Data Sheet 22: Screeds: mortar.org.uk
- Designing Buildings Wiki, Screed over underfloor heating: designingbuildings.co.uk
- Mapei Topcem technical data sheet: cdn.shopify.com
- Ronacrete, Drying of Screeds: ronacrete.co.uk
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.