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Guide to Self-Levelling Compounds

Self-levelling floor compounds help level up surface irregularities on new and existing substrates. Komerco's range of self-levelling compounds are easily mixed and simple to apply, they find their own level giving a smooth finish for laying tiles or other floor coverings.

Levelling compounds are typically used internally and applied up to 30-50mm in depth. Self-levelling compounds for use in external areas are available and include: Soudal Pour & Level, SikaFloor Level Ultra & SikaFloor Level 30. For deeper pours products such as MasterTop 515 can be blended with aggregate which helps dissipate the heat of the reaction, or specialised deep-pour products such as the MasterTop 530 or SikaFloor Level Eco can be used.

It’s important to remember that many levelling compounds are not suitable as a finished, wearing surface, and that it is best to speak with the manufacturer or Komerco representative for suitable applications. 

Self-levelling compounds are suitable with most screeds, including sand/cement, anhydrite and flooring grade asphalt. However, when levelling timber floors, or screeds containing underfloor heating then general purpose levelling compounds should not be used. Fibre-reinforced products such as Sika FiberLevel 4020 or latex additives such as Bostik's Megalastic as a replacement for water addition should be considered for these applications. Always check the products you’re using with the manufacturer and/or the TDS's to make sure they’re suitable.

Before laying a levelling compound it is essential to ensure that correct preparation of the sub floor is carried out. Firstly ensure that the floor is structurally sound with a minimum pull off strength of 1.5 MPa. Then ensure the surface is clean, firm, dry and free from grease, dust and any other contamination which may be considered barriers to adhesion. 

Any new concrete or screed must be left to fully cure according to the manufacturers’ instructions before applying any levelling compound. Ensure that any direct-to-earth sub-floors incorporate an effective damp proof membrane or moisture barrier. If the concrete substrate has efflorescence or high moisture (RH) and moisture sensitive flooring is being installed then a suitable moisture or moisture vapour barrier should also be installed. 

The majority of subfloors will also need priming. Priming ensures that the levelling compound fully adheres to the substrate. The required primer to use can depend on the substrate and the levelling compound. For porous substrates, products such as the MasterTop 1600, SikaFloor Pro Primer or 01 Primer can be used. For non-porous substrates Sika Floor Prep N Prime  or PrimeGrip Non-Porous should be used. If levelling over timber boards where the joints are open, then a thin heavy duty tape can be used to bridge the gaps.

When mixing self-levelling compounds, ensure the manufacturer’s instructions are followed at all times. These can be found on the technical data sheets, product packaging or from the Supplier or Komerco representative. Typically, levelling compounds are mixed by adding powder to clean water. We would generally recommend mixing with a heavy-duty electric drill mixer at a slow speed for a minimum of 3-5 minutes until a lump-free mortar is achieved. Not mixing for the recommended time or additional water may result in product irregularities and possible product failure.

Once the required consistency is achieved, pour the mix over the prepared substrate and spread to the required depth using a suitable steel finishing trowel or long handled blade. Work the mixture well into the corners, edges and around projections. When you’ve finished spreading the mixture on the floor, pour some more mixture onto the floor and spread that out and blend it in with the previous area.

Before allowing to cure, ensure that the surface is sufficiently smooth to receive floor coverings without any further treatment. If you are laying tiles or slabs, floors should be corrected to SR1 (Surface Regularity) – this is plus or minus 3mm or less over a two meter straight edge. Using spiked rollers on fibre-reinforced products can pull fibres through to the surface, so always read the technical data sheet or speak with the manufacturer for advice. If any trowel marks do remain, rub down before the compound has hardened.

Freshly applied levelling compounds must be protected from damp, condensation and all forms of water while curing for at least 24 hours. Areas of application must have fresh airflow to assist with product hydration and drying. Closed off rooms with no fresh air will retard the curing/drying process and possibly lead to product failure.

Always allow the new floor to set before laying your finished floor surface. Setting times can vary depending on the chosen product normally between 4 to 24 hours and is dependent upon your floor finish. This is to ensure that the covering is fully protected from any moisture in the screed which will diffuse through the screed and damage the surface if not left to fully cure.