Concrete vs screed
A concrete slab is the structure: it carries the floor and sits on the hardcore and membranes. A screed is the layer on top that gives a flat, level surface at the right height for the floor finish, often over insulation and underfloor heating pipes.
In an Irish house the slab is at least 150 mm (TGD C). A floating sand and cement screed over insulation in a house is at least 65 mm.
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Slab and screed side by side
| Concrete slab | Screed | |
|---|---|---|
| Job | Structural: carries the floor | Levelling: a flat surface for the floor finish |
| Aggregate | Coarse stone, such as 20 mm (D20) | Sand, or up to 10 mm in a fine concrete screed |
| Minimum depth in a house | 150 mm, ground-supported (TGD C) | 65 mm floating sand and cement; liquid screeds thinner |
| Sits on | Hardcore, blinding and membranes | The slab, or insulation |
| Standards | I.S. EN 206 and the Building Regulations | BS EN 13813 and BS 8204 |
How they go together
- Hardcore and membranesAt least 200 mm of compacted, gas-permeable hardcore, blinding, the DPM and, in a High Radon Area, the radon barrier and sump.
- The slabAt least 150 mm of concrete, tamped or floated.
- InsulationRigid boards on the slab, if the insulation isn't under it.
- PipesUnderfloor heating clipped and pressure tested.
- ScreedSand and cement or liquid, to the depth the floor zone allows.
- Floor finishOnce the screed tests dry.
Everything on screeds
Screed types, depths over heating pipes, drying times and prices are covered in detail on our sister site, floorscreeding.ie: see types of floor screed and screed drying time.
Floors laid 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. He pours concrete floors, slabs and foundations as well as screed. 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”
Quoted word for word from JAM Floor Screeding's Google reviews. Read them on Google
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Concrete vs screed questions
Is screed the same as concrete?
No. Concrete is structural, with coarse aggregate. Screed is a levelling layer of sand and cement, or a flowing screed, laid on the slab or on insulation.
Can the concrete slab be the finished floor?
Yes. A power floated slab can be the finished floor in a garage, workshop or shed. In a house, a screed on top covers the insulation and pipes and sets the level.
How thick is the slab and how thick is the screed?
In a house, at least 150 mm of concrete (TGD C) and, for a floating sand and cement screed, at least 65 mm.
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