LEVEL HEADED ADVICE


Bostik looks at the key considerations when controlling the drying rate of levelling compounds to ensure a successful flooring installation.


When it comes to applying subfloor preparation products there are many factors that can prevent or indeed encourage them to dry out.


Levelling compounds both dry and cure and the reactivity of the binders will be affected by the temperature and humidity on site, along with how the products have been stored since manufacture.


So what needs to be considered when working with levelling compounds to ensure they dry and cure properly?


STORAGE OF PRODUCTS Cold, damp storage conditions will slow down even the fastest setting products to some degree. If you are relying on the fast setting nature of a product for a work time programme, then make sure you store your bags and bottles in a warm environment (at least 24 hours for single bags and several days for pallets) before you plan to use them.


SITE CONDITIONS The site conditions also have an important role to play and a nice, warm environment is the key to a successful flooring installation. It is worth remembering that chemical reactions are slower the colder it is.


For standard levelling compounds the delay in drying and curing times due to cold, damp sites can be significant and mean waiting days before you can continue flooring works. If you can’t get conditions improved or haven’t the job size to allow waiting, then look to use a fast setting option, such as Bostik’s Screedmaster Speed 30, but bear in mind these will also be slower than their stated drying time if temperatures are low. In all instances, a temperature of below 5o


“For standard levelling compounds C will be a


serious problem, as it will affect the curing of the binders and may result in long-term issues.


APPLICATION THICKNESS Another factor affecting the drying rate is the thickness that the product is applied. Drying times are often based on a 3mm thickness, but if you’re applying thicker than 3mm there is more moisture to escape, so you may need to factor in more time.


It is very difficult to tell if a levelling compound has dried sufficiently and most contractors use their instinct based on how it looks, however the colour change can often be misleading and more of a surface effect. A pin meter is a good way of assessing if the compound is anywhere near dry. A reading up in the red or a surface very easily compressed by the pins shows it is not cured or dry enough to lay on.


THE ROLE OF LEVELLING


COMPOUNDS ON ADHESIVES As most floorcoverings including vinyl, linoleum, rubber and many backed carpets are relatively impervious, it is critical


36 | LEVELLING COMPOUNDS


the delay in drying and curing times due to cold, damp sites can be significant and mean waiting


days before you can continue flooring works.”


to provide somewhere for moisture to dry into. This is where the levelling compound or substrate comes into play. A 3mm levelling compound that is laid onto an impervious base such as a DPM will provide enough absorbency for the adhesive to dry (once the initial open time is allowed). If you have less depth of levelling compound then it can get to a stage where the adhesive saturates the levelling compound and cannot continue to dry. This can result in a poorly bonded floorcovering or bleed through of adhesives at joints, or even discoloration of the floorcoverings. Bear in mind that even at 3mm thick, it is necessary that the levelling compound is also dry. If the substrate under the levelling compound is absorbent then the criticality of the compound depth is less significant.


www.bostik-profloor.co.uk www.tomorrowscontractfloors.com


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