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Mick Hooper, Flooring Manager at global product manufacturer and supplier, Sika, looks at how self-levelling screeds help simplify and improve the flooring installation process.

For flooring that looks as good as it performs, it is imperative that the supporting surface is also of the highest quality. Any flooring project requires a detailed assessment of the subfloor to ensure its compatibility with the surface selected to cover it, be it wood, carpet, vinyl or tiling. Wood, for example, can cup or warp if too much moisture is present in the finished subfloor, similarly bubbles can appear in sheet vinyl. A functioning damp proof membrane (DPM) such as Schönox SDG will eliminate such issues. Its installation is therefore recommended regardless of the finished flooring.

BE PREPARED Before any levelling compound materials are applied, the floor itself must be thoroughly prepared, cleaned and free from dust and debris. Surfaces which are especially friable or dusty must first be primed with an acrylic/ water solution to help consolidate and seal the surface, as this will reduce the amount of imperfections in the cured levelling material. Similarly, any old bituminous layers or existing adhesives must be completely removed to ensure the best possible bond is achieved with the parent substrate and provide a finished surface that is flat, even and defect-free throughout.

Once the parent substrate has been prepared, if it is established that no DPM or underfloor heating is present and the subfloor’s moisture content >75%RH is too high, a surface-mounted


liquid DPM must be installed prior to applying the levelling screed.

The use of a high-quality, self- levelling screed is essential to ensure that subfloors can be quickly and professionally prepared and are in a fit state to accept the chosen flooring product once dry and fully-cured. Delivering a smooth, flat surface that is completely defect-free is a speciality of Sika Schönox, a self-levelling screed which provides the ideal surface onto which the new finished floor can be laid.

Supplied as a powder in easy to manage bags, Schönox self-levelling screeds are mixed with water before simply being poured or pumped onto the prepared surface. From a practicality perspective however, it is important to first identify the areas in which dips and valleys occur in order for the levelling screed to be poured accordingly.

On smaller areas using a straight edge, such as a level, it is easy to see where these occur and can be marked accordingly so that they can be worked on first to bring the room to an even level. On larger projects, a level survey should be carried out to ascertain the degree of levelling required.

Working in this way, it is possible to keep waste to a minimum, which can further help to keep all important costs down. Once applied, the screed should be left to cure completely before being opened to traffic, with some Schönox screeds this can be in as little as 60 minutes.

DRY RUN The next stage in the process is to lay the chosen flooring material. However, it’s vital to test the moisture levels in the floor to ensure it is dry enough to take the chosen floorcovering. By definition, a dry reading should be below 75% RH or 2.0% CM (carbide method) moisture content by weight depending on the type of test carried out. By adhering to these simple procedures, it is possible to ensure flooring projects become error-free.

To make the process as straightforward as possible, the use of specially- designed, self-levelling screeds, primers, DPM’s and adhesives such as those available from Sika Schönox, eliminate substrate concerns whilst providing reassurance to the professional floor layer and the end user that the floor will take any dynamic loading placed upon it, without adverse effects further down the line.

Whilst there is no short-cut to quality, durable flooring in terms of planning – details, however small, should receive the utmost attention at the earliest stage – the availability of high-performance, cost-effective, self-levelling products has helped simplify the installation process without compromise to performance. It gives credibility to the conclusion that there is no longer any excuse for poor- quality flooring.

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