Flatten & Smooth (legacy)

A self-levelling compound is a cement-based underlayment poured onto a floor to flow, settle and form a flat, smooth surface. It removes minor dips, undulations and surface defects so the floor covering or coating has the flat base it needs to bond and perform correctly.

Use a levelling compound when the subfloor is level but has shallow dips, trowel marks or minor surface defects — typically from a feather edge up to 30-to-70 mm. Use a screed when the floor needs a new level, a build-up in height, or a shaped drainage fall. Many jobs need both: a screed to form the level, then a leveller to smooth it.

Most levelling compounds in this range accept foot traffic in three to four hours and are ready for vinyl, carpet or tile from 12 to 24 hours. Timber coverings typically need 24 hours. Heavy traffic and coatings may need 48-to-72 hours. Times are shorter at warmer temperatures and longer when it is cold.

Some can. RLA True Level Flexi is fibre-reinforced and rated for solid timber, particleboard, existing ceramic tiles and even liquid waterproofing membranes. Other compounds are concrete-only. Always check the approved substrate list — a primer is usually required, and no compound in this range should be used where rising damp is present.

Usually yes. Priming seals the substrate, prevents rapid water loss that causes pinholes and weak edges, and helps the compound bond. Some smoothing and skim products can go on porous concrete unprimed, but a primer is recommended for non-porous or burnished surfaces. Check each product for its primer requirement.