Renovation technique
Pouring Liquid Screed Over an Existing Concrete Slab
Existing slab? You have three choices — bond to it, isolate on plastic, or float on insulation. Each has a different minimum depth.
A renovation almost always starts with an existing slab. The decision is whether to bond the new screed to it, isolate it with plastic, or float it over insulation with UFH.
The choice sets the minimum depth and drying time. Pick wrong and you'll either crack it or wait months.
Build-up options
| Type | Minimum depth |
|---|---|
| Bonded to primed slab | 25mm Cemfloor / 30mm anhydrite |
| Unbonded on DPM only | 35mm Cemfloor / 40mm anhydrite |
| Floating on 100mm PIR + UFH | 50mm Cemfloor / 55mm anhydrite |
Prep matters more than depth
- Bonded: shot-blast or acid-etch, prime with SBR
- Unbonded: 1200-gauge DPM, lapped and taped
- Floating: insulation edge-taped, foam perimeter
Frequently asked
Pouring over an existing slab?
Tell us the slab age, condition and target finish. We'll spec the right build-up.