Apart from being a fundamental requirement of any project, the adhesives and installation aspects of the flooring industry go hand in hand, making this sector one of the fastest-moving in terms of new systems, developments and formulations, and in this feature we detail the pre-floor requirements, the correct adhesives to be used, and the installation methods that are necessary to ensure that the floorcoverings meet or even exceed the relevant specifications.
Many of the internationally acclaimed flooring adhesives are imported or sold in this country through subsidiary companies and appointed agents but, in terms of development, quality products, availability, and formulations to meet the specific needs of the market and the climatic variations throughout the region, these are well matched by the locally manufactured products.
In addition to a wide range of adhesives, the sales programmes of the local manufacturers provide smoothing compounds, resin flooring systems, repair mortars, floor screeds, bonding liquids, damp-proof membranes, and grouts to meet any installation requirement.
In recent years the adhesives industry has developed products to meet the demands for the use of fewer volatile organic compounds (VOC), thus reducing emissions and odours that can contribute to respiratory problems and poor air quality in buildings – and these can now be classed as ‘environmentally friendly’ in every respect.
To establish what constitutes a quality flooring adhesive, these are generally a combination of binders (polymers and resins) that provide adhesion; fillers (usually very fine aggregates) which give the product the volume which influences the required working consistency; and a liquid (water and/or solvent) so that the adhesive is workable during application and adhesion is developed as the adhesive dries.
However, although many of the earlier adhesives were produced with the use of a high proportion of solvents, this is not the case today as the regulations covering health, safety and environmental requirements have demanded a discontinuance or considerable reduction of their use in adhesive products.
In addition, the various types of floorcoverings and their requirements have changed, which means that they need adhesives with higher performance levels to accommodate the installation of a wider range of floorcoverings on any type of subfloor.
Let’s take a look at what the preferred adhesives are for the various types of floorcovering, and the recommended installation techniques for each:
The types and requirements of vinyl floorcoverings have grown considerably over the years and this has required an improvement in adhesive technology to ensure that they are adequately and consistently adhered.
This means that acrylic-based and pressure-sensitive adhesives have become the products of preference for a large number of flooring contractors who demand high performance from adhesives when fitting vinyl floorcoverings. Pressure-sensitive adhesives that can be allowed to dry completely before fixing are becoming increasingly popular with flooring contractors.
A two-part polyurethane adhesive is usually preferred for installing vinyl (sheet, tile or LVT), and PVC and rubber tile and sheet, and other resilient floorcoverings can be installed using this product. It is classed as a reactive resin system where two components are mixed together and a chemical reaction takes place so that it will cure and harden sufficiently in 4-6 hours to take foot traffic.
No water or solvents are used in its manufacture, so it has a very low emission level and its strength characteristics make it ideal for fixing floorcoverings in areas subjected to high loads such as sports centres and industrial premises. It is also suitable for floors being installed above floor heating systems.
When installing resilient floorcoverings, a perfectly smooth subfloor is essential – anything less than perfect will affect the appeal of the surface finish of the flooring.
To achieve this, a wide variety of primer coatings designed to consolidate the substrate and fill any cracks, and self-levelling screeding compounds is available to provide a perfectly smooth substrate surface for installation of the floorcoverings.
Wood, Laminates & Bamboo
The technological advances in this sector of the floorcovering industry are legion (see the separate introductory articles for each type in this issue), but mostly each of these materials favour a floating floor finish with the advent of the modern installation systems.
The ‘click’ or self-locking installation used on these floorings largely dispenses with the need for adhesives, but where there is a need to glue the floor to the substrate, a polyurethane adhesive or the new ‘elastic’ adhesive system is the modern answer.
Some of these flooring systems favour a tongue-and-groove fixing – and these do need a traditional wood flooring adhesive which works by creating a bond between the substrate and the flooring through a chemical reaction. Here a one-part polyurethane adhesive is preferred because in use it allows for the movement between the planks that often takes place once they are installed.
This is also used where these floors are stuck down, but in these cases a damp-proof sealer or moisture barrier must be applied to the substrate before the floor is installed. Locally made liquid adhesives for batten systems are also available.
The elastic adhesive mentioned above is an adhesive mat for laying floors; a system which obviates the use of screws, nails, glue or clips completely for the laying of parquet and strip floors. Strong, screwed and complex sub-constructions were needed in the past to prevent movement of the wood as far as possible, but nowadays one finds mostly floating floors, not fixed to the surface, and using tongue-and-groove connections.
By using the elastic adhesive mat, the wooden sections are pressed together on the mat which has been laid on the subfloor, and then the protective layer between the floor and the mat is removed. Because of the heavy adhesive layer, this is a unique laying system and subfloor in one which pulls the floor segments together almost seamlessly.
While all adhesives work on the same principle of changing from a liquid to a solid state, they differ in the carrying agent or catalyst that activates them. The most common types of wood flooring adhesives include the following:
Water-based adhesives certified as ‘very low emission’ are the first choice for health and environmental protection. They are free of solvents or VOCs and safe to install. However, their range of application concerning certain types of wood or subfloor is limited.
Solvent-based adhesives are well proven for wood floor installation over several decades, offering a large range of application, but they contain non-hazardous solvents which are said to evaporate during the first weeks after installation is completed.
Urethane-based/moisture-cure adhesives offer the largest range of application and the highest installation security but are usually more expensive than other adhesives. These can be applied under almost any circumstances and have hardly any restrictions on the type of wood or subfloor.
Ceramic, porcelain and natural stone
The three main categories of setting materials that are used for these floors are mastics and cement mortars, and epoxy adhesives. Mastics are pre-mixed and easy to use, but they are weak compared to cement mortars and don’t hold up under exposure to water, so they are not recommended for floors or use in wet areas.
Epoxy adhesives are commonly used for industrial flooring applications. These are usually high performance, three-component, epoxy-based adhesives used for a variety of materials, ensuring full bond and maximum adhesion.
Because of its high strength and resilience, this type of adhesive is ideal for bonding ceramic tile, pavers, acid-brick, and steel floor plates in areas where there is heavy wheeled or foot traffic, impact or abrasive wear, or thermal shock.
Cement mortars, of which there are several varieties, are strong and can stand up under exposure to water and many other stresses placed on a tile installation.
Cement mortars are often called ‘thinset mortars’, which come in powder form and must be mixed with either water or an acrylic additive (some powdered thinsets have an additive already blended in); these have a stronger bond and are more flexible than pre-mixed adhesives.
They can also support considerable weight, so they are often favoured for flooring installations, particularly as they can be used in wet areas as well as those exposed to heat.
Thinsets are often available in dark grey or white – the latter favoured for light coloured tiles, but if a light-coloured grout is being used, it is preferable to use the white thinset.
Let’s look at the other options:
Cement-based Tile Adhesive
This type of tile adhesive is used for general tiling on solid concrete floors, and is generally cheaper than other types of tile adhesive as it is a basic, cement-based non-flexible adhesive. This adhesive should not be used on cracked cement floors or where some movement is expected. It is supplied dry and is mixed with water before being applied.
Modified Cement-based Tile Adhesive
This tile adhesive is often modified to cope with small amounts of movement. It has rubber and polymers in it so that if the substrate cracks or moves slightly the tile will not crack. Modified cement adhesive can be used both inside and outside and is a great choice for floors. Is supplied dry and is mixed with water to use.
Fast-setting Tile Adhesive
This type of adhesive is ideal for fast-track installation and is used when the tiles need to be in service within 12 hours. It is suitable for vitrified tiles such as porcelain or natural stone such as marble, granite, sandstone or slate – and products providing 2-hour, 6-hour and 12-hour settings are also compensated for high strength and shrinkage.
Polymer-modified adhesives with enhanced bond strength, flexibility and water resistance are also available and these high-end products require only the addition of water for mixing, thus minimising the risk of mixing errors on site.
When installing any type of natural stone floor it is essential to take the advice of the supplier, because the differences in colour, structure and porosity will determine what type of adhesive should be used.
A carpet adhesive is regularly used instead of carpet tacks for keeping a carpet well-grounded and in place, and for installing wall-to-wall carpet and carpeting on stairs.
Carpet adhesives come in two main types – pre-applied and spreadable. Carpets with pre-applied (adhesive-backed) make carpet installation a simple matter, and pre-applied, pressure-sensitive adhesives are very popular for use with carpet tiles that may need replacing in heavy-traffic areas.
Other adhesives come in a spreadable form and must be applied to the carpet backing with a trowel or a roller. These adhesives are more versatile and can be used for a wide range of carpeting, including smooth or coarse-backed carpets, soft underlay, urethane-laminated underlay and so on, but it is necessary to match the right type of spreadable adhesive to a particular type of carpet backing.
Check with the supplier or manufacturer, because if the carpet adhesive and carpet backing combination is not correct, the installation will be less than perfect. The type of carpet adhesive to use also depends to a large extent on the type of substrate on which the carpet is to be laid, because it is important for the adhesive to bond well with the substrate.
In line with the current passion for environment friendliness, many modern carpet adhesive companies are going green, and in most cases their products use water as the vehicle; they are also generally non-toxic and non-flammable. The other ingredients, such as binders, fillers, preservatives and viscosity controls, are in turn selected to be safe and less volatile.
The adhesive can be acrylic-based or synthetic-rubber-based. Before applying the carpet adhesive, it is advisable to test the substrate for moisture, as this may prevent the adhesive from setting effectively. Also, once the adhesive is spread, the carpet should be laid immediately, positioned and rolled with a heavy roller.
Once this is done, the adhesive should be left to dry properly. Avoid walking on the carpeted area for a day or two. The carpet adhesive, depending on the quality, will usually keep the carpet firmly in place for several years.
As can be seen from the preceding text, the use of adhesives and the methods of installation go hand in hand in the provision of a perfect floor and, rather than produce a detailed textbook-style, step-by-step description of how the various flooring products should be installed, we have linked this to the preferred adhesive and given basic background information on fixing methods for each.
However, there is no doubt that whatever is seen to go wrong with any installation the blame is always levelled at the flooring contractor first, largely erroneously.
The problems of surfaces being provided by the main contractor that are less than suitable or even unfit for the floorcovering to be installed; the ‘rush’ at the end of fast-track projects, often to the detriment of the flooring installation; the running out of budget and other reasons for substituting specified floorcoverings with something cheaper – these are but a few of the many problems that installers are regularly faced with.
To get the perspective straight ‘from the sharp end’ we spoke to Peter Grant, managing director of Leicester Floors in Pinetown, for his views on these problems and what may need to be done to overcome them.
There is no doubt the biggest or most recurring problems faced by flooring contractors today are the floor preparation (often not done or badly done), and moisture in the floor screeds is another common problem.
The substrates are often unfit for flooring to be installed on due either to lack of detailed specification, or not enough attention paid to the site work. This is such a crucial requirement for any floorcovering that the architect or project manager should personally make sure that the installer is provided with a perfect and clean surface to work on, or the end result will be a considerable waste of time and money to put it right, or a flooring installation that is doomed to failure from the start.
Moisture is the perennial problem (see separate article on this subject in this issue). Obviously the answer is to allow the concrete to dry out thoroughly before any work is started on it, but this is a slow process and the main contractors almost always short-circuit the drying procedures because time becomes the problem.
Peter Grant says the contractor should wood-float the topping screed to give it the best chance to dry and then use a moisture barrier and self-levelling screed of 3mm-5mm just before the installation. “This obviously has cost implications but it is the safest way to get a good floor and ensure that the client gets his building on time,” he says.
Fast-track construction is here to stay, and unfortunately this always seems to adversely affect the installation performance of the flooring contractor, mainly because the flooring is normally one of the last trades in for obvious reasons.
This means that the installer generally has less than the programmed time to do the installation, in which case Peter says this often means bringing in “less talented” installers to speed up the installation. “The only solution is to have a more realistic programme to work to, but this is never negotiable by the contractor or the client,” he says.
Installation of vinyl flooring often provides problems, for the reasons stated earlier, but in addition to that Peter says that vinyl sheeting brings its own difficulties, and more training is required on a continual basis, with regular refresher updates.
Those in the flooring industry regularly complain that the architect’s specification is often changed or not adhered to, although this is not seen as a problem by the professionals (see Specifiers and Specifications in this issue), but most installers will tell you that there are contractors that do this on a regular basis, hoping to make a bigger profit on the change.
Peter says that at Leicester Floors they always advise the manufacturers when they know about it, but the manufacturers should track this down and report it to the architect or client, particularly if they got the product specified in the first place.
There is no doubt that the experienced and reputable flooring contractors provide an excellent service in the provision of well-installed floors, but with the pressures put on them by the professionals and other trades, the installer is often the fall guy when things go wrong.