Flow screeds are designed to provide a smooth, level surface that’s often more cost-effective and quicker to install than the traditional sand and cement alternative. Click-system wood floors can usually be installed over a suitable underlay without any further preparation to the screed. However, where bonding is required for tongue and groove boards, preparation is needed to ensure a strong and stable surface to adhere to.
Here’s our quick and handy guide to preparing a gypsum, calcium sulphate or anhydrite screed for a successful wood floor installation.
Check the Relative Humidity (RH)
Make sure it’s below 70%. Take measurements at various points across the floor using a digital hygrometer. If there’s underfloor heating, we recommend a maximum of 65% RH. Liquid damp proof membranes don’t work well on flow screeds so we advise that the screed should be thoroughly dried.
2. Prepare a Sound Surface
A finished flow screed usually has a few millimetres of soft milky laitance on its surface, and this has no inherent strength. Sanding or grinding is necessary to remove this laitance, and the surface should then be vacuumed to ensure no loose material remains.
3. Test and Turn off Underfloor Heating
If there’s underfloor heating, make sure this is fully tested before installing the wood floor. Switch it off and allow it to cool down before any surface preparation products or adhesives are applied.
Prepare the surface for levelling using a suitable primer such as Woodpecker Level-X Primer.
Apply a layer of fibre-reinforced levelling compound and allow it to dry. This provides the surface strength needed to ensure the flooring is securely bonded down.
6. Sticking Down
We recommend a flexible adhesive that will allow for natural movement in the wood – see our MS Parquet Adhesive. Allow 2 to 3 days for the adhesive to cure before switching on UFH.