Steve Dykes goes into detail about considerations that should be taken when preparing a subfloor.
LVTs are classified into different types depending on where they’re installed and their level of use. The thickness of the wear layer is an important quality characteristic which should be considered. The wear layer of an LVT is usually 0.3mm to 0.7mm thick. The thicker the wear layer, the more durable and wear-resistant the floorcovering is. On certain commercial installations, it’s recommended the wear layer be a minimum of 0.5mm.
Good preparation is paramount for a successful installation of LVT floorcoverings. Product selection is key to achieve optimum results and provide longevity of the installation to the end user. To ascertain which products are needed for a project, evaluating the area in which the LVT floorcovering is to be installed is essential.
Some of the key points should be:
- Subfloor identification
- Age of the building
- Subfloor moisture content
- Is the subfloor heated?
- Are there areas of solar gain?
Identifying the substrate is crucial for successful LVT installation as it determines the required preparation methods, product systems, and work steps. For example, sand and cement screeds, calcium sulphate screeds, and timber subfloors have specific preparation needs owing to their unique properties. Sand and cement screeds are absorbent and can shrink and crack, while calcium sulphate screeds have low shrinkage but are moisture sensitive. Using the recommended products for each substrate type ensures a high-quality flooring installation. Sand-cement and concrete subfloors are among the most common substrates encountered.
Proper subfloor preparation involves inspecting for contamination, cracks, strength, absorbency, moisture, and unevenness. Mechanical preparation of subfloors is by far the most efficient way to remove surface contamination such as existing smoothing compounds, adhesive residue and paints etc. Some products may form a laitance on the surface, which must be removed. When using grinding machines, it is important to select the correct segment for specific situations. There is a wide range of different grinding segments available to effectively remove the various types of residual material left on the subfloor once the floor covering has been removed.
Failure to have a subfloor free from contamination can compromise any installation, leading to costly replacement and damage to your company’s reputation.
Routine testing of the substrate for moisture is a crucial step and depending on the specifics of the job site, should be conducted in accordance with BS 8203 2017: The RH (Relative Humidity) readings from this test will determine the percentage moisture content within the subfloor. The information gathered will inform the flooring contractor whether a moisture vapour suppressant system is required, and which system is best suited for that specific location. This could mean using a two-part epoxy DPM if a structural damp-proof membrane cannot be evidenced, or a single component suppressant for subfloors that have a residual moisture content above the recognised British standard relative humidity percentage figure of 75%RH. If the floor is deemed dry (<75% RH) on absorbent substrates containing a structural DPM, and the building is of an age that there’s a construction DPM incorporated in the building, then it’s recommended that a suitable primer and smoothing compound can then be applied, without risk of failure.
The performance of LVT is in part, reliant on the correct selection and application of the adhesive. For areas subject to mild solar gain and temperature fluctuations, a high-temperature adhesive should be applied in accordance with the manufacturer’s own specific recommendations. Modern day buildings may have localised areas that are subject to extreme temperature fluctuation and high solar gain. South-facing conservatories, bi-fold doors and floor to ceiling windows may exceed the capabilities of some HT adhesives, resulting in expansion and contraction at the header joints on LVT floorcovering. Areas that are subject to extreme temperature fluctuations, require a different type of adhesive. One-component heavy duty hybrid adhesives, or 2-component adhesives should be used in localised areas where ambient conditions can negatively affect LVT floorcoverings.
Pressure-sensitive adhesives are widely used for the installation of LVT floor coverings. Traditionally, the term ‘pressure sensitive’ means that the adhesive would be allowed to ‘flash off’ to a dry tack. However, UZIN does not recommend installing LVT floor coverings utilising this method. Alternatively, LVT floorcoverings should be applied into this type of adhesive while it’s in a wet or semi-wet state. Using this method results in sufficient transfer of adhesive on the back of the LVT floorcovering, creating the strongest bond at the interface of the floorcovering and the subfloor.
The application of preparation materials and the installation of the floorcovering are best achieved by following the recommended application process. The equipment used is paramount to ensure successful installation. For example, the recommended notch size is crucial when applying adhesives to transfer adhesive sufficiently onto the underside of the LVT. Specific LVT hand tools are available for speed and accuracy when cutting LVT flooring to installed border work. The recommended weight pressure roller (ideally 68 kg) should be used to roll floorcoverings, forcing the material into the adhesive bed, ensuring optimum transfer of adhesive.
Taking sufficient time to evaluate the area before installing the LVT properly and choosing the correct products and tools in accordance with UZIN or WOLFF’s recommendations will ultimately result in a successful installation. If you require further help or advice regarding the above products and tools, please do not hesitate to contact our technical team. They’ll be happy to discuss the best products, machines and tools to suit the requirements of your specific projects.
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Steve Dykes is northern technical manager at Uzin Utz UK