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Don’t Get Stuck Over Choice Of Adhesives

Paul Jarvis, regional technical consultant at Altro, explains why adhesives can be the key to flooring success or failure: 

THERE is no doubt about it, adhesives can be a sticky business. Every contractor may know about when and how to use adhesives but there are many times when the process can go wrong, having a potentially devastating effect on the job.

Manufacturers produce different adhesives for specific purposes and selecting the right adhesive for the right job is absolutely critical. Most flooring manufacturers make recommendations about which adhesive is best to use with their product and many of them provide guides to help with the selection process.

Using a good quality product will give you peace of mind but make sure that it is stored correctly and within date when you apply it – most adhesives have a shelf-life of about 12 months, after which time there could be problems with the curing process.

It sounds obvious, but it is vital that the adhesive is used in accordance with the manufacturer’s instructions and, if applied correctly, it is very rare for it to fail. Not only is this important in producing the best results but it’s also crucial in order to comply with the flooring manufacturer’s warranty, which could be made void if the wrong adhesive is used or applied incorrectly.

The adhesive chosen must be fit for purpose so consider where it is going to be used, the condition of the substrate, and the environment in which you will be applying it. For example, water-based adhesives are not suitable for showers, wet areas, or areas where spillages are likely to occur and, if accidentally applied, will soften and result in the lifting of the floor once it becomes damp.

We’ve all heard the saying ’if you fail to prepare, prepare to fail‘ and in the case of applying adhesive and making a quality bond, preparation is everything. In the first instance, substrates need to be in accordance with the Code of Practice BS8203 and BS8204, which says, the subfloor must be of such quality and strength as not to dust or break up under working conditions. The subfloor must be dry and smooth.

If direct to earth, the subfloor must be protected against water vapour and rising damp. The subfloor must be free from dust, grease, paint, polish or any other contaminating agent, even at a microscopic level, as they will interfere with the adhesive bonding to the surfaces sufficiently. Prior to the installation of the floorcovering, the subfloor should be tested in accordance with BS8203 to achieve a relative humidity reading of below 75% R.H. If not, consider using a surface damp proof membrane.

Of course, the right surface preparation is only one element of the application process. The environmental conditions are equally as important, with room temperature and moisture content impacting on the process. Low temperatures adversely affect the performance and curing characteristics of the adhesive. Most manufacturers recommend that the minimum room temperature should be around 14 or 15degC.

Moisture-based products, which rely at least in part on evaporation, can’t cure if the air is already damp so the atmosphere needs to be relatively dry in order to be successful.This is particularly relevant if pressure-sensitive adhesives are being used on dense subfloors such as asphalt or power floated concrete; installing the flooring into the adhesive before the product has reached its receptive state will result in failure every time.

Even when the conditions are right, problems can still occur. For example, some less expensive polyurethanes may not contain sufficient moisture scavengers and, if applied to a damp substrate, can foam slightly, resulting in lumps and bumps that may be visible on the surface of the flooring.

There is further risk of an uneven surface if you don’t use the right tool to apply the adhesive. Over the years I have witnessed contractors using a trowel to apply adhesive when tacky, leaving ridges on the adhesive surface, which can in time lead to the adhesive lines shadowing through. One good way of avoiding this is to finish the application of the adhesive by using a paint roller to even out the surface and flatten the ridges left by the trowel.

Of course, sometimes problems can’t be avoided, in which case the only solution is to take-up the flooring, resolve the issues and start the process again.

This article has been reproduced from the Contract Flooring Journal website. You can find them at