Not all vinyl is the same

Martin Cummins

Published by Martin Cummins - UK Technical Support Manager, Bostik

Martin has been involved in the industry for over 20 years. He’s passionate about flooring in all its guises, with his particular expertise being in subfloor preparation products and adhesives. Martin is an active member of the CFA manufacturers committee and he sits on the CFA council. He aims to keep abreast of all the changes in the industry and feeds this knowledge back to installers to make sure when floors are laid they perform to their maximum potential.

If a successful, long lasting installation of new vinyl flooring is going to be achieved it is important that you have accurate product information, have considered the area in which it is being applied and, finally, it’s crucial that you ensure the correct adhesive selection is made.

A key component of vinyl products (or PVC for the purists) is that they are flexible and contain materials called plasticisers.

Temperature is very important when it comes to vinyl installations – if laid in the cold, vinyl products can not only be difficult to manipulate and shape but, once the area has warmed up, they will also try to expand and put tension on all welds, joints and edges.

Sheet vinyl

Vinyl can be broadly split into two categories – sheet vinyl and vinyl tile products. Simply put, sheet vinyl comprises of layered products (heterogeneous) and non-layered products (homogenous). Vinyl tiles cut down from sheet can be considered in the same manner as sheet vinyl in most cases. Luxury vinyl tiles (LVT) are a different story. These are manufactured to give high design quality and utilise many layers. They result in a very strong material which is not particularly highly plasticised but poses challenges in resisting movement on the floor when installed. Bostik works alongside floor covering manufacturers to ensure adhesives appropriate to the floor covering and the site installation can be partnered together.

The most straightforward products to install are homogenous products on absorbent subfloors. A standard, quality acrylic adhesive with good grab and plasticiser migration resistance is all that is needed here.

With heterogeneous products, the type of adhesive used needs to be totally solvent free in addition to the properties mentioned above. Solvents can cause discoloration of the surface of the vinyl. This is generally observed as happening on cap and cove installations where a solvent based contact adhesive may have been used. Even the most fastidious contractors can never be sure all the solvent has evaporated, particularly in winter installations, so it is prudent to either use a quality, double sided adhesive tape or a solvent free contact adhesive.

There are occasions when the subfloor/substrate does not have a high level of absorbency. This could include an acoustic underlay system with rubber and cork or an isolator membrane. In these cases, a wet stick adhesive is not going to work so you need to look at an appropriate dry stick or chemical cure adhesive to ensure no moisture is trapped between the two impervious layers.  Both these have challenges for sheet flooring installation. If using a pressure sensitive adhesive it will have quite a high residual tack, so you need to ensure that the vinyl is laid exactly where it needs to be bonded as there will be little chance to manipulate or slide into place. Avoiding air pockets is also essential. Chemical cure adhesives can be laid into wet, but the floor needs to be kept traffic free for the full cure time, which can be over 24 hours in some circumstances.

If there are concerns of moisture getting under the vinyl, for example in wet rooms, it should be bonded with a water-resistant adhesive such as an epoxy or PU product. Where high temperature fluctuations are likely to be present, such as in conservatories and glass fronted areas, the use of a genuine high temperature adhesive is essential. This applies to the whole range of vinyl products under these conditions, not just homogenous and heterogeneous sheet.

Luxury Vinyl Tiles (LVT)

When it comes to LVT products, the industry is rapidly changing. LVT is no longer just narrow strips of short length (0.1m x 1.0m nominally), but can now be significantly wider and longer (up to 0.25m x 1.2m) to mirror timber or ceramic flooring. This is making LVT a very attractive product for designers, but does pose more potential issues for installers. The issues simply relate to the tension within the product as it tries to “move” under temperature fluctuations. The key is understanding if and where there is likely to be movement.

In a typical area which does not experience aggressive sunlight, a high-quality resonated pressure sensitive adhesive can be chosen. The pressure sensitive aspect helps a lot in the installation of these products, particularly where bespoke designs are being used which needs time to plan and lay. The resins make the adhesive robust as well as nice and tacky, so it will cope with typical room temperature fluctuations.

It is worth noting that around ovens and in areas where hot water pipes run close to the floor’s surface, vinyl flooring should be bonded with a high temperature (HT) adhesive to enable the tension and potential movement to be controlled. There is nothing worse than a beautifully laid design floor with a couple of gaps or bubbles in it due to the vinyl shrinking or expanding.

Underfloor heating

When it comes to subfloors with underfloor heating (UFH), further questioning is required. A warm water UFH installed correctly should never exceed 28oC at the glue line, which, provided the heating remains switched on throughout the winter months, should not pose any problems for the adhesives already suggested above. However, when it comes to electrical heating, our experience is that the temperature control on this is much more erratic. This is due to the ease of manipulation for the householder and also the proximity of cables to each other and the depth of smoothing compound applied over them. We would therefore always advise that for electrical underfloor heating you utilise either a high temperature adhesive or use a resonated pressure sensitive but lay into it wet… don’t wait for the adhesive to tack off. This greatly increases the bond strength of the adhesive.

Bostik’s comprehensive range of vinyl flooring adhesives includes solvent free products such as sheet vinyl adhesive, high temperature grade adhesives, resin modified products, as well as pressure sensitive adhesive tapes and water resistant adhesives for wet areas.

 

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