What is a floating screed?
A floating screed (in Dutch zwevende dekvloer) is a screed that lies completely loose on an insulating or acoustic layer and is nowhere in contact with the structural floor, the walls or other parts of the building. It “floats” on that intermediate layer. As a result, impact sound such as footsteps and scraping chairs is passed on much less to the structure, and so to the neighbours or the floor below.
Build-up (from bottom to top)
- Structural floor: the concrete slab or load-bearing floor.
- Possibly a levelling layer to accommodate services and create a flat base.
- Insulation or impact sound layer: for example rigid insulation boards and/or a dedicated acoustic layer.
- Separating membrane, so the screed does not run between the boards.
- Edge strips: soft strips along all walls, columns and pipes.
- Screed: sand-cement or flowing screed, possibly with underfloor heating.
The key detail: no sound bridges
A single rigid connection between screed and wall can undo much of the effect. So:
- Edge strips everywhere, including at door frames, pipes and stairs.
- Trim the edge strip only after the floor finish has been laid.
- Do not fix skirting or tile skirting rigidly to the floor; leave a flexible sealant joint between floor and skirting.
- Do not cast pipes rigidly into both screed and wall.
- Keep mortar out of the edge joint during pouring.
Things to watch
- Because the screed is not supported by the substrate, it needs to be thicker and stronger than a bonded screed. The required thickness depends on the screed type, the load and the compressibility of the insulation; follow the supplier’s and applicable standards’ requirements.
- Large areas and underfloor heating require movement joints.
- Let the screed dry properly and check residual moisture before laying parquet or vinyl.
Related terms
- Screed
- Poured screed
- Anhydrite screed
- Expansion joint
- Shrinkage
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