Special Who has adhesives for different screeds in combination with floor heating ?

CAN WE RECONCILE WOOD WITH FLOOR HEATING? YES, WE MOST CERTAINLY CAN!

USING THE RIGHT ADHESIVE IS A MAJOR FACTOR FOR A SUCCESSFUL PROJECT

Photo – Blanchon

One of the biggest challenges for parquet floor fitters is undoubtedly to fit a wooden or parquet floor onto floor heating. To do that job, it is essential to consider carefully all the phases of the work to ensure that the end result is immaculate. One of the main things to consider is the use of the right adhesive in combination with the type of subfloor or screed used.

In the past, we have extensively covered relative humidity and temperature, the right wood choice, floorboard sizes, fitting method, and the substrate. Yet what do you look out for when glueing a wooden or parquet floor? To help answer that question, we consulted specialists from the BBRI, namely BBRI (WTCB) Contact no. 43 (3-2014) entitled: ‘Can parquet and floor heating be reconciled?’ Glued fitting

As all professionals know, wood is a very hydroscopic material which adapts to the surrounding hygrothermal conditions and at the same time is subject to dimensional changes. All this isn’t just a matter of avoiding things like extreme and rapidly changing relative humidity and temperatures. It also involves using the right type of adhesive during the fitting.

The BBRI instructions could not be more clear. We literally read the following: ‘Only a glued (or glued-nailed) fitting is recommended to allow the best possible heat transfer through conduction of the heat via the floor to the indoor surrounds. Glueing with adhesive wires is not recommended due to the presence of air layers under the floor, which increase the thermal resistance of the complex.’

Rigid or elastic adhesive?

It is advisable to use either a rigid or an elastic adhesive specially for fitting parquet onto floor heating. Obviously, the type of adhesive is chosen to suit the conditions. With rigid adhesives (e.g. dispersion adhesives or dual-component polyurethane adhesives), the BBRI notes how these types of adhesives make it possible to limit the movements of the wood, but they do put more pressure on the substrate. That can result in the parquet coming loose and/or a breakage in the substrate in extreme conditions. And so, the use of this type of adhesive requires a strong substrate (minimum cohesion of 0.8N/mm²). If you opt for a flexible adhesive (e.g. STP adhesive or MS polymer adhesive), you should realise that this restricts the pressure, but the wood will move a lot more. The more elastic the adhesive, the more pronounced the movements and distortions of the wood, whereby, according to the research centre, a certain aesthetic annoyance can arise. In the absence of planks of a large (> 10) slenderness factor (width-thickness ratio), you should therefore remember that a highly elastic adhesive can result in distortions (editor’s note: this refers to the joints curling or opening). These exceed the permissible criteria on the technical sheet TV 218 without the distortions necessarily being irreparable. To put it more simply, as soon as the indoor conditions become more favourable again, the planks return to their normal position.

Good advice

Some good advice to conclude: If you use this type of adhesive, it’s best to tell the project manager that the wood movements may be quite obtrusive. For the rest, they say that the rigidness or elasticity of the glue will have less effect if the wooden floor used has more dimensional stability.

An overview

Blanchon

Blanchon strongly endorses the warning that there are clear rules (the steps plan) for using floor heating with parquet. Over time, an adhesive can lose its ‘plastic’ under the influence of heat (through gradual evaporation), something which can be a health hazard. The adhesive can then become breakable and the floor can come loose. Hybrid polymers possess few softeners and that is an advantage. Moreover, these adhesives adhere to any healthy screed and possess the necessary elasticity. The hybrid polymers AB 1300 (traditional glueing up to 130mm wide and 260mm for multilayer) and AB 2000 (up to 200mm and 400mm for multilayer) are adapted for floor heating. These are available in pliable aluminium bags of 6kg and packed in pairs in cardboard. These adhesives are flexible and elastic, they offer excellent adhesion, they are easy to apply, and they provide a firm adhesive groove. They are in class AC1R.

Bona

Glueing a wooden floor requires not only skill, but also reliable products and durable tools. To fit a wooden floor you need an adhesive which is suitable for the task in hand. This requires the right balance between strength and elasticity to lay the ideal base to be sure of a firm foundation and an ongoing high-performance floor. Regardless of the subfloor, damp, or unevenness, Bona has the products which you need, from primers and levelling agents to high-quality adhesives. The choice for a particular adhesive depends on the subfloor and working method. Bona has developed various products for various situations which are all designed solely for wooden floors. Reactive silane adhesives: These include Bona Quantum, the Bona all-round parquet silane adhesive with an integrated damp screen. Bona silane adhesives are long-lasting and reliable glues with strong adhesion and they can generally be used without a primer. They set quickly and contain no isocyanates or solvents. They are compatible with floor heating. Primers: These include Bona D501, a primer for preparing absorbent and non-absorbent substrates prior to using Bona silane or polyurethane adhesives. Applying a primer improves the condition of the substrate or prepares it perfectly for the next coat of levelling agent or adhesive. Damp screens: These include Bona R590, which block the rise of damp from the subfloor, and that’s essential since the presence of residual moisture can cause untold damage to wooden floors.

Chimiver

ADESIVER 501 EP is an odorless, free of solvents and water two-component epoxy-polyurethane adhesive. This adhesive is classified as "HARD-ELASTIC" according to ISO 17178. Destinations: suitable to lay all kinds of wood and in any size including strips, without requiring the pre-laying of wood joists and with previous suitable treatment onto not absorbing preexisting subfloors (ceramics, tiles, marble, palladian, gres, etc). Suitable for gluing onto heated subfloors.

Dinachoc

DINACHOC C901 – THE PROFESSIONAL HYBRID ADHESIVE They offer DINACHOC C901 adhesive for use in combination with parquet and wooden floors when the whole structure has to be compatible with floor heating at high and low temperatures. They recommend this in combination with the Dinachoc S801 subfloor to ensure excellent acoustic insulation. And so, the fitting is done with double glueing. If we consider the preparation for application on site, their DINACHOC C901 adhesive is used without an adhesive primer and it adapts to all types of bearer (tiles, concrete screed, anhydrite screed, wood, ceramics, natural stone, etc.), all widths (even extra wide), and all sorts of wood. Remove all grease and dust from the bearer for the best possible adhesion. Their adhesive composition is the fruit of years of progress in the search for the ideal formula and includes no isocyanates, silicones, solvents, or formaldehydes. Moreover, VOC content is also very low. The adhesive is graded as A+ and its EMICODE® class is EC1PLUS, the highest EMICODE® grade.

Emfi

For glueing wooden floors onto floor heating we recommend full glueing with EMFIPARQUET PRO PLUS and/or EMFIPARQUET PRO ECO. The DTU 51.2 recommendations for preparing the bearer must be respected. The room temperature must be above 10°C, the humidity of the bearer must be under 3% for a concrete screed and under 0.5% for an anhydrite screed. You must also ensure that the bearer is clean, sufficiently interlinked, and adapted for fitting parquet. The adhesives which we recommend for fitting onto floor heating are the same as those recommended for fitting floors with no floor heating. The composition is the same. Finally, to ensure that you use the right adhesive, you must make sure the product is not past its expiry date. You will find that information on the packet.

Thomsit

All Thomsit parquet adhesives are suitable for glueing wooden flooring onto floor heating. Both elastic adhesives (such as the Thomsit Flextec glues) and non-elastic adhesives can be used in combination with floor heating. It is more a question of the floor fitter’s personal preference whether to use an elastic or non-elastic adhesive. We tend to recommend elastic adhesives because they usually offer a little more comfort, such as, for instance, Thomsit P 675, P 685, or P 695. These glues have permanently strong adhesion, are easy to apply, and are highly elastic. These products do not contain any water or solvents and any stains can be removed easily. The Thomsit primers and adhesives hardly affect the heat resistance, and the type of screed doesn’t play any further part here. For more information you can visit their web site: www.thomsit.be.

Bostik

Hybrid adhesives are the most universal of all parquet adhesives. Their strong elastic properties make them absolutely ideal for use in combination with floor heating. Bostik has several types in its range. The WOOD H 550 ECO PLUS is based on the unique AXIOS TRI-LINKING technology and combines a good adhesion with fast setting. And so, this adhesive is absolutely ideal for fitting wide solid wood floorboards and composite parquet safely. When fitting wooden floors onto floor heating it is important to respect the maximum surface temperature for the covering floor, namely 27 to 28°C. If the temperature is too high, the wood will show cracks, which lead to ongoing damage.