Stephen Boulton, technical service manager at F. Ball and Co. Ltd., provides advice on repair and finishing compound selection.
A PERFECT FINISH
Contractors should begin any flooring installation by ensuring the subfloor is suitably sound, smooth and dry enough for the receipt of new floorcoverings. As part of this, F. Ball recommends the application of a levelling compound to achieve a smooth base. However, there will be occasions where prior preparation is required; where sand/cement screeds are mechanically damaged or ceramic tiles are missing, for example. When working over plywood subfloors, it will also be necessary to fill gaps between joints. If left unfilled, these can transfer to imperfections in subsequently applied levelling compounds or floorcoverings, which can compromise the appearance of the finished installation. For these situations, it helps to be aware of the variety of repair compounds and finishing compounds available.
It is important that a moisture test is undertaken to determine subfloor moisture levels before any remedial work takes place. Where a moisture test indicates that the relative humidity (RH) level within the subfloor is above 75% (65% if wood floorcoverings are to be installed), the application of a waterproof surface membrane will be required before floorcoverings are installed. If not treated, high levels of humidity within the subfloor can lead to a loss of bond strength, ultimately resulting in floor failure. The requirement for a waterproof surface membrane will also have a bearing on repair compound selection and application.
SUBFLOOR TYPE In the case that a contractor finds that the subfloor has dormant, non-structural cracks or holes in it, which may be the case where sand/cement screeds have been mechanically damaged, a suitable repair compound should be used to fill in the gaps. F. Ball’s Stopgap 400 Repair is a fast-setting, rapid-drying repair compound that can be applied in thicknesses between 2-50mm to repair internal floors in light to heavy duty areas. Stopgap 400 Repair can also be used to fill gaps in tiled areas where individual ceramic tiles are missing.
Where excess subfloor moisture is detected, contractors should use a repair compound that is designed for use in damp
conditions, such as F. Ball’s Stopgap 460 Exterior Repair, prior to the application of a waterproof surface membrane. Stopgap 460 is weather resistant, so it can be also used to repair external floors as part of refurbishment projects.
When working over plywood subfloors, gaps between planks, as well as holes caused by screws used to affix them to the substrate, should be filled prior to the application of a levelling compound. Stopgap 500 Micro is a rapid-drying floor finishing compound for creating a smooth surface over plywood and other rigid, dry, absorbent surfaces, prior to the installation of floorcoverings. It is supplied as a pre-blended dry powder, which is mixed with water and trowel-applied to create a seamless, feathered edge.
NEXT STEPS Once a repair compound or finishing compound used to smooth imperfections in the subfloor has dried, contractors can then proceed with the application of a levelling compound or installation of a new floorcovering in the usual way, remembering to prime the subfloor beforehand. Priming serves to promote the adhesion characteristics of levelling compounds and adhesives when applied over non-absorbent surfaces, such as ceramic tiles. When used over absorbent surfaces, primers stop the unacceptably rapid drying of subsequently applied levelling compounds. Primers also prevent pinholing: tiny bubbles formed by the slow escape of air from the subfloor, which burst on reaching the surface, leaving small pinholes as the levelling compound cures.
Finally, levelling compound selection should be determined by the subfloor type and intended use. When working over flexible subfloors, including plywood, a flexible levelling compound, such as F. Ball’s Stopgap 700 Superflex, is recommended to accommodate movements in the subfloor, which can cause other levelling compounds to crack. Heavy duty levelling compounds, such as F. Ball’s Stopgap 300 HD, are available for areas that will be subject to subject to heavy loads or high foot traffic.
www.f-ball.com/en
ON THE BALL:
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