Screed types · checked 29 October 2026
Fibre-reinforced screed
Fibres or mesh in a sand and cement screed: where they're needed and what they change.
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Figures checked against each source on 29 October 2026. How we check
Fibre-reinforced screed is a sand and cement screed with short fibres mixed through it as reinforcement. Reinforcement matters most when the screed floats on insulation and has nothing underneath to grip.
Gyvlon says a floating sand and cement screed needs either D49 mesh or fibre reinforcement. Designing Buildings Wiki notes that with fibres the minimum depth over underfloor heating may drop from 65 mm to 50 mm.
Where fibres or mesh come in
- Floating screeds. Over insulation, a sand and cement screed has nothing to grip. Gyvlon lists D49 mesh or fibre reinforcement as required for a floating sand and cement screed.
- Underfloor heating. The screed heats and cools every day. Designing Buildings Wiki gives 65 mm as the usual minimum for sand and cement over heating, and says fibres can bring that down to 50 mm.
- Some fast binders ask for mesh, not fibres. Mapei asks for reinforcing mesh over the pipes in a Topcem screed with underfloor heating, and steel mesh on compressible substrates.
- Limecrete. Tŷ-Mawr's limecrete mix includes screed fibres.
Sources: Gyvlon flowing screed general data pack (Anhydritec); Designing Buildings Wiki, Screed over underfloor heating (last edited 15 September 2020); Mapei Topcem technical data sheet; Tŷ-Mawr, What is the Sublime floor (22 March 2024). Checked 29 October 2026.
What fibres don't fix
Fibres don't replace the right depth, proper curing or joints. The Mineral Products Association's figures still apply: 65 mm minimum floating in housing, at least five days under polythene to cure, and the slab or insulation flat and firm. Joints still go over structural joints and between heating zones.
Source: Mineral Products Association, Mortar Data Sheet 22: Screeds (Issue 3, October 2023). Checked 29 October 2026.
- Floor finish
- Fibre-reinforced screed Fibres spread through the full depth.
- Polythene
- Insulation
- Slab
Questions to ask
- Fibres or mesh, and why for this floor
- What depth, and whether the fibres change it
- The fibre dose, from the fibre maker's data
- Curing and joints, which fibres don't replace
Questions people ask
Do I need fibres in my screed?
For a floating sand and cement screed, Gyvlon lists D49 mesh or fibre reinforcement as required. Ask your contractor which they use and why.
Can fibre screed be thinner over underfloor heating?
Designing Buildings Wiki says fibres can bring the minimum over heating down from 65 mm to 50 mm. Check the depth against the product's own data.
Do fibres stop all cracking?
No. Depth, curing and joints still matter. The MPA asks for at least five days of curing under polythene for a sand and cement screed.
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
- Designing Buildings Wiki, Screed over underfloor heating: designingbuildings.co.uk
- Mapei Topcem technical data sheet: cdn.shopify.com
- Tŷ-Mawr, What is the Sublime floor: lime.org.uk
- Mineral Products Association, Mortar Data Sheet 22: Screeds: mortar.org.uk
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