SMOOTHIN Here, BAL talks us through the necessity for levelling compounds an

An essential component of any tiler or tiling contractor’s tool box, levelling compounds ensure that any surface irregularities with new or existing floor bases are corrected.

So why do subfloors need to be level before tiling? Well British Standards recommend that floors should achieve SR 1 surface regularity for the laying of floor tiles or other floorcoverings. SR1 is a max deviation of plus or minus 3mm over the length of a 2m straightedge. Anything above this can cause the vertical displacement between the edges of two adjoining tiles – otherwise known as ‘lippage’.

Floor levellers, which are available as either one-part or two- part products, are self-smoothing and thus ‘find’ their own level, helping to ensure floors achieve SR1 surface regularity.

There are numerous levelling compounds on the market, each with different features and benefits. Generally, they can be applied from anything from 3mm to 40mm thick – however in some instances where further height build-up is required then more than one application, or the addition of bulking materials may be required.

Alternatively, contractors can opt for a specialist, deep filling levelling compound or an all-in-one product such as BAL Level Max. BAL Level Max can used from 3mm right up to 80mm (in localised areas) in one application. When using at 80mm over a larger area, it may be suitable to use an aggregate, such as BAL Course Aggregate, to bulk out the product and reduce costs.

Because of its unique formulation, BAL Level Max can be walked on after three hours and tiled after only four hours at any depth. This ensures fast-track project completion.

Self-levelling compounds are suitable on most substrates, including concrete, sand and cement screeds and calcium sulphate (anhydrite) screeds following the use of a suitable primer such as BAL Prime APD.

Further considerations need to be taken when levelling a rigid stable timber floor, or a screed containing underfloor heating. In these instances, fibre-reinforced products – such as BAL Level Max – are particularly suitable.

BAL Level Max is formulated with our unique Fibre Strand Technology (FST). First developed for our Max-Flex Fibre tile adhesive, FST is the result of exhaustive investigation into the used of certain microfibres combined with high-quality, super smooth fillers. The microfibres in BAL Level Max deliver greater strength, and improved performance including better flow and pourability.

Because of the microfibres, we don’t recommend spike rolling the product, as this can bring fibres to the surface and potentially cause issues with the bonding of tiles and other floorcoverings to the substrate.

When using self-levelling compounds, the key to a successful installation is preparation of the sub-floor you are smoothing.

Firstly, it is imperative that any new screed is left to fully cure. For sand/cement screeds this is a minimum of three weeks,


and six weeks for concrete screeds. With anhydrite/calcium sulphate and hemi-hydrate screeds, the screed should be left to dry until moisture contact is below 0.5% water by weight or 75% RH (Relative Humidity).

All screeds should be free from efflorescence, laitance, dirt and other loose materials. This can be achieved with a mechanical sander and is especially important with anhydrite screeds, as laitance can cause a barrier between the self-levelling compound and the screed, potentially causing failure.

Where the subfloor is direct-to-earth, check that an effective damp-proof membrane – such as BAL DPM – is incorporated.

As previously mentioned, most screeds will need priming before levelling – typically two coats, with a second coat applied at 90° angle to the first.

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