Special Producers of levelling agents which thicknesses can we apply in one treatment and what about the drying time?

DON’T FORGET THE PITFALLS

YOU CAN ONLY LEVEL PERFECTLY BY FOLLOWING THE RULES PERFECTLY

Luc Wouters (business developer of floor technology for Belgium at Bostik -B)

‘Your basic knowledge lays a nice base.’

Bostik is a specialist in adhesive systems and its products are used all over the world in scores of applications, from production and industrial assembly to hygienic disposables. This wide range also includes solutions for the building industry, from new construction to renovation and for both residential and commercial settings.

As part of these construction solutions, Bostik offers an extensive assortment of levelling compounds. Luc Wouters, business developer of floor technology for Belgium, is the ideal person to tell us more about this. Luc has over 34 years of experience at Bostik and he supports his contacts and colleagues by giving advice for substrate preparation and providing training courses. Luc explains: ‘Floor technology comprises all products for repairs to covering floors, damp screens, levelling compounds, and wall and floor adhesives. Bostik has products and suitable materials for all phases of a project.’

The playing rules which lead to expertise

His first piece of advice is: ‘Analyse the base and the floor. The levelling compound to be used depends on the type of floor. Whether you fit ceramics, carpet, PVC, linoleum, or parquet, each floor has specific requirements which you have to consider. Elements like drying time, required layer thickness, strength, and flexibility must be considered.’

‘With a flexible floor covering like PVC or linoleum, you need a very flat substrate for a seamless end result. You can’t flatten out any unevenness with adhesives. With parquet it’s a different matter. A higher adhesive consumption, and therefore a thicker adhesive layer, means you can remove any unevenness. Moreover, great compressive and tensile strength are absolutely vital to solid parquet since the wood constantly affects the substrate. And so, each fitting needs the right levelling compound.’

As we’ve already said, another requirement is the layer thickness. All levelling compounds have their own maximum applicable layer thickness. Luc Wouters comments: ‘In practice, not all substrates are equally flat, so it’s possible that you have to offset 4mm in one corner, whilst you have a much bigger difference in the other one. The Bostik levelling compound SL C940 XL (SL = self levelling and C stands for cementbound) can even be applied up to a thickness of 5cm. The SL C780 FLEX is ideal for levelling a wooden substrate. It is a fibre-reinforced levelling compound with great bend strength.’

The next piece of advice for professionals is always to respect the stated dosage with water. He says: ‘The last thing you want is a powdery end result. And so, you must stick strictly to the pre-scribed quantity of water to be added. Bostik always gives these instructions clearly on the pack.’

Some products considered

Bostik offers a wide range of levelling compounds, which are easy to apply. This SL C510 PRO is suitable for use on indoor floors. SL C510 PRO is certified in accordance with EC 1+ and is thereby suitable for use in BREEAM and LEED projects. SL C750 POLYRAG from Bostik is a fast-drying, flexible, and fibre-reinforced levelling compound specifically for levelling less stable substrates, such as wood, for instance. This product is ideal for a further finish with a floor coating.

Bostik’s fastest drying levelling compound (also suitable for use in great layer thicknesses) is the SL C990 SPRINTER. Originally, fast-drying levelling compounds were designed for use in shops and public areas where speedy and smooth renovations were needed. Closure time must be kept to a minimum. By opting for fast-drying levelling compounds, you can fit a new carpet or tile floor within two to four hours.

Developments and the environment

Finally, we discuss innovations in the field of levelling compounds. He says: ‘Generally on the market, but also particularly at Bostik, the players are making every effort to provide ecological solutions. For instance, all our levelling compounds possess at least emission certificate EC1 or even EC1+. And so, they’re absolutely ideal for use with green projects (BREEAM and LEED).’

Photo – Bostik

An interesting question about levelling agents is the thicknesses with which they can cope nowadays. Obviously, we want to know what thicknesses we are talking about and how much is possible in a single layer. Then, we mustn’t forget another vitally important element: What about the drying time?

We called upon specialist Bostik and they told us at once that every levelling agent has a maximum layer thickness. With standard levelling agents you can assume a maximum of 1cm. For the project market levelling agents are customary with a maximum thickness of 20mm. Bostik informed us that there’s even a separate type which can go up to 5cm. The latter is used mainly for renovations of rooms with a very irregular floor surface. Generally speaking, you can say that most standard levelling agents are applied in layer thicknesses of between 3 and a maximum of 5mm. In this case, what you level today can be sanded the next day and you can fit the floor at once. In exceptional cases where you level up to 5cm thick, you should allow for a drying time of 1cm per day, but even then you add one extra day to be absolutely sure.

Three general rules

An important point with levelling is that you have to take account of the drying time. There are three rules of thumb for doing that: The temperature of the base plate has to be at least 15°C; the surrounding temperature should be at least 18°C; and the humidity has to be between 45 and 75%.

If you fail to take account of those factors, things will soon go wrong. Suppose, for instance, that you level at a temperature of 8°C. This means that your product is going to flow very badly and that the levelling layer will take an eternity to dry. If the humidity is too high, condensation can form which falls on the levelling agent, and this means that it will take a long time to dry.

Take care when combining layers

We would like to know whether it is possible to apply two layers of levelling agent (or even more) on top of each other. The general answer is that you can, but only under strict conditions. What you always have to do is read the maker’s instructions carefully. If the instructions say that the maximum thickness is 2cm, it is simply not feasible to reason that you can apply a first layer of 1.5cm, allow it to dry, and then apply another layer of 1.5cm on top because you have to come to 3cm. A prescribed maximum of 2cm of levelling agent means just that. Applied specifically to 2cm, applying a layer of 1cm twice is perfectly possible and can be useful if you are working on a floor with a slight ‘slope’.

Use the correct primer

Finally, we were informed that the importance of using the correct primer cannot be overstated. Generally, there are three types of primer. The first one is for porous substrates, the next one is for smooth and non-porous substrates, and the last one is for application to a wooden substrate. The second type of primer (for smooth and non-porous substrates) has an in-built sand grain. This is necessary for obtaining a good adhesion of the levelling agent to the smooth surface (think of tiles, for instance). The third type of primer (for wooden substrates) in particular needs more explanation. It’s asking for trouble to apply a levelling agent directly to a wooden substrate. The wood absorbs the moisture, swells, and shrinks again after drying. You can guess the result. This type of primer should ensure good adhesion and will protect the wooden substrate from the mixing water in the levelling agent. Moreover, the primer fills in any cracks between planks to prevent leaks of the levelling agent.

Do not choose for the layer thickness

One more point: Generally speaking, the advice with levelling agents is not to choose on the basis of the layer thickness. On the contrary, you take account of the substrate, the type of floor covering which you want to fit, and the use of the room. Never forget that the amount of traffic plays a very big part, so a bedroom requires a different approach to that of the entrance of a public area.

Bona

In the Bona assortment: 3 levelling agents and 1 repair agent. These products are suitable for floor heating and have low emissions (Emicode EC1 Plus). Bona H600 Cement-bound levelling agent reinforced with acrylic polymer. Self-levelling – Fitting is possible after 12 hours. Compatible with primers Bona D510, D520, or Bona R590. Fill unevenness or bigger holes with Bona H610. For application under: ∫ mosaic, engineered, multilayer, and solid parquet ∫ Also under flexible floors, textile floors, and solid cork tiles ∫ Layer thickness: 1-20mm Bona H605 Calcium sulphate levelling agent: Based on alpha-hemihydrate. Yields flat and absorbent substrates ready for the installation of floor coverings. Self-levelling – Low pressure. Compatible with primers Bona D510, D520, or Bona R590. For application under: ∫ Flexible floors ∫ Textile flooring ∫ Also for parquet which is glued with Bona silane adhesives ∫ Layer thickness: 1-20mm Bona H660 Cement levelling agent. Like Bona H600, but with a somewhat longer drying time. Treat the substrate with a suitable primer such as Bona D510, D520, or Bona R590. Fill unevenness or bigger holes with Bona H610. For application under: ∫ mosaic, engineered, multilayer, and solid parquet ∫ Also for under flexible floors, textile floors, and solid cork tiles ∫ Layer thickness: 1-20mm Bona H610 Cement-bound repair agent: A fast-setting and fast-drying grout with no leaks for indoor repairs. Substrates should be treated with primer Bona D510, D520, or R590. Application: ∫ Ideal for filling holes and cracks in covering floors ∫ Repairing and renovating staircase steps and risers ∫ Repairing and renovating sand-cement screeds and concrete floors ∫ Repairs around pipes, doors, and window frames ∫ Layer thickness: no limit.

Chimiver

"RASOCHIM MAXI", Fast drying self-levelling compound for interior works and public floorings

RASOCHIM MAXI is a fast-hardening, single-component grey cement powder premixed, for thickness from 5 mm to 40 mm and suitable for indoor use. RASOCHIM MAXI mixed with water becomes fluid cement paste suitable for realization of excellent strength self-leveling smoothing. The product matures quickly both on new and old subfloor. It does not undergo any shrinkage, it does not form cracks, it has good resistance to compression, bending and abrasion. It is possible apply on sand screeds, cement screeds, ready to use screeds, ceramic floors, marble, natural stones, wood, clinker and grès.