ON THE LEVEL
A guide to using self-levelling compounds by David Wilson, UK Technical Services Manager at Building Adhesives Ltd (BAL)
Self-levelling floor compounds help level up small surface irregularities on new and existing bases and usually come in one-part or
two-part forms. Easily mixed and simple to apply, they find their own level giving a smooth finish for laying tiles or other floorcoverings.
Most levelling compounds can only be applied up to 30-40mm and will need to be used in more than one application or with other materials required. However, there are some exceptions on the market such as BAL Level Max which can be applied from 2mm up to 80mm in one application.
It’s always important to remember that levelling compounds are never suitable as a finished, wearing surface, and that they should always be covered.
Typically, 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 only fibre- reinforced products are suitable. Remember to check the products you’re using with the manufacturer to make sure they’re suitable.
Before laying a levelling compound it is essential to ensure that correct preparation of the subfloor is carried out. Firstly ensure that the surface is
34 | LEVELLING COMPOUNDS
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. Make sure that any direct-to-earth subfloors incorporate an effective damp proof membrane.
The majority of subfloors will also need priming. Priming ensures that the levelling compound fully adheres to the substrate. If levelling over timber boards where the joints are open, we would suggest using thin heavy duty tape to bridge the gaps.
When mixing your self-levelling compound always ensure you follow the manufacturer’s instructions. Typically, products like BAL Level Max are mixed by adding powder to clean water five parts powder to one part clean cold water by weight. We would always recommend mixing with an electric drill mixer at a slow speed i.e. under 300rpm. Always mix until a lump-free mortar is achieved and allow the mixed leveller to stand for two minutes before re-mixing for 30 seconds.
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 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 floorcoverings without any further treatment. We would not recommend the use of spiked rollers on a fibre- reinforced product, such as BAL Level Max, as this can pull fibres through to the surface. If any trowel marks do remain, rub down before the compound has hardened.
Always allow the new floor to set before laying your finished floor surface. Setting times can vary between 4 to 24 hours depending on your chosen product and is dependent upon your floor finish. For example, BAL Level Max can be tiled after 4 hours, but must be left to set for 24 hours for other finishes.
Finally, we would always advise checking with the manufacturer or their technical advisors for before application to ensure project success.
At BAL our Technical Advisory Service is fully equipped to provide support to contractors, architects and tilers using levelling compounds – including NBS M40/M10/M20 specification assistance, on-site consultancy and expert technical advice.
www.bal-adhesives.com
www.tomorrowscontractfloors.com
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