Depths · checked 29 October 2026
Screed depth for underfloor heating
How much screed goes over the pipes, product by product, and how to plan the floor zone.
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- Sources under every figure
Figures checked against each source on 29 October 2026. How we check
Over underfloor heating, liquid screeds need at least 25 mm of cover over the pipes: Roadstone, Cemfloor and Gyvlon all give that figure. A floating sand and cement screed in a house is normally at least 65 mm deep in total.
The total depth is the pipe plus the cover. On a typical floor that's 50 mm for Roadstone FlowPlus in a house, and 65–75 mm for sand and cement.
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.
Minimum depths, maker by maker
Sources: Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023); Designing Buildings Wiki, Screed over underfloor heating (last edited 15 September 2020); Roadstone FlowPlus cement liquid screed brochure (RS.BRO-19 Rev 01, March 2022); Gyvlon flowing screed general data pack (Anhydritec); Cemfloor Complete technical data sheet (2023). Checked 29 October 2026.
- Floor finish
- Screed Total depth = pipe + cover. 25 mm cover minimum for the liquid screeds above.
- Polythene
- Insulation To a U-value of 0.15 W/m²K in a refurbishment with underfloor heating (SEAI).
- Slab
Planning the floor zone
The floor zone is everything between the slab and the finished floor level: insulation, screed and floor finish. SEAI's technical standards set a floor U-value of 0.15 W/m²K where a refurbishment includes underfloor heating, against 0.36 without, so the insulation is thicker when heating goes in. In an existing house, raising the floor means skirtings, doors and the bottom stair all need checking.
Source: SEAI Domestic Technical Standards and Specifications (v4.0, July 2026). Checked 29 October 2026.
Gyvlon's advice for a deep floor zone is to fill it with insulation and keep the screed to its minimum, since screed is what takes months to dry.
Source: Gyvlon flowing screed general data pack (Anhydritec). Checked 29 October 2026.
Not too deep either
Roadstone recommends FlowPlus is laid no more than 80 mm deep, because more depth slows drying. On the 1 mm a day rule for the first 40 mm and 2 days per mm after, 80 mm would take about 120 days.
Our arithmetic from the Roadstone FlowPlus brochure rule, checked 29 October 2026.
Bays and joints over heating
| Screed | Heated bay | Joint rules |
|---|---|---|
| Roadstone FlowPlus | Under 40 m², max 8 m long | Joints between separately controlled heating circuits, heated and unheated screed, areas of high heat gain |
| Cemfloor Complete | 100 m² | See the data sheet |
| Gyvlon | 300 m², 20 m long, 6:1 | Joints between independent heating zones and at door thresholds |
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.
Questions people ask
What is the minimum screed depth over underfloor heating?
25 mm of cover over the pipes for Roadstone FlowPlus, Cemfloor Complete and Gyvlon liquid screeds. Sand and cement: normally at least 65 mm total in a house.
How thick is liquid screed over underfloor heating?
Roadstone gives 50 mm total for FlowPlus over heating in a house, with 25 mm over the pipes. Gyvlon gives 25 mm minimum and 30 mm nominal cover.
Can screed be too thick over underfloor heating?
Roadstone recommends no more than 80 mm for FlowPlus because deeper screed takes longer to dry. Gyvlon recommends extra insulation rather than extra screed in a deep floor zone.
How much insulation goes under underfloor heating?
Enough to reach a floor U-value of 0.15 W/m²K in a refurbishment with underfloor heating, under SEAI's standards (from TGD L). The thickness depends on the insulation used.
Sources (5)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Mineral Products Association, Mortar Data Sheet 22: Screeds: mortar.org.uk
- Designing Buildings Wiki, Screed over underfloor heating: designingbuildings.co.uk
- Roadstone FlowPlus cement liquid screed brochure: roadstone.ie
- Gyvlon flowing screed general data pack (Anhydritec): specifiedby.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.