The Cold Weather Can Leave You Guessing
Martin Cummins won’t lay in his conservatory this winter Part 2
LAST month I discussed problems using surface DPMs and primers in cold, stagnant buildings where there is little air movement and subsequently moisture. This month: smoothing compounds and adhesives.
A smoothing compound is needed on virtually all modern flooring projects to ensure an absorbent medium for adhesives, a consistent smooth surface and to isolate from previous installations. All smoothing compounds I refer to require the mixing of a liquid (either water or a polymer/latex system) with a dry powder consisting of binder, sand and additives.
The purpose of the liquid is primarily to create a fluid material for trowelling onto the floor, but inclusion of polymer also aids adhesion. The powder system reacts with the water in the liquid and cures to give a strong smooth surface ready to receive flooring.
Under good drying and curing conditions the products are generally designed to enable
flooring to be laid over the next 24 hours. There are some products highly modified with various cement systems enabling them to cure and allow floorlaying within a few hours and there are some products between
In all cases though there is a requirement for the products to react and use up mix-water and also to lose some water through evaporation before they are suitable for laying flooring onto. The amount of water required to be lost by evaporation is key with some faster curing products ‘locking in’ moisture rather than relying on
We know that reactivity rates reduce as the temperature does; evaporation rates also decrease as humidity increases and the temperature drops. It stands to reason that under cold, damp, stagnant environments smoothing compound curing rates will be greatly affected.
A premium product, quoted as four hours to lay onto may require overnight to reach the point to lay on. Whereas a product that states a curing time of 24 hours may need several days before it is ready to lay on. Strength development (walk on time) will also be greatly affected, so you should factor this in as well.
I have been on many far from ideal sites where the pressure to get areas completed is the over-riding factor and there I have found minimal attempts to assist the floorlaying.
I recently had a long discussion with a main contractor who was doing ‘his best’ by warming the area with a fuel burning space heater (that actually gives off moisture) and sealing the doors with polythene (consequently preventing airflow) to keep the warmth in.
I had to credit him with his endeavours, whilst also trying to get him to appreciate the limitations.
He was switching off heating throughout the night and all windows were being secured, limiting the opportunity for the compound to cure/dry. He understood the limitations but still was unable to assist any further, primarily as the cost of heating was prohibitive.
Fortunately a good working relationship with the flooring contractor enabled larger areas to be released enabling levelling to be completed and left for at least two days before flooring. This is far from normal with pressure to lay being the primary aim.
Even when there is time to let smoothing compounds cure fully there is still a major issue with the installation of the flooring itself. Both the adhesives and floorcoverings are compromised by low temperatures and stagnant moisture/air conditions.
Arguments for adhesives are similar to that for primers. With regard to water-based adhesives (the vast majority of contract products nowadays) a cold thick adhesive will not trowel or roller as designed and, more importantly, will not tack off in the expected manner if cold and/or damp environments are encountered.
This can be seen most dramatically with pressure sensitive adhesives (i.e. adhesives where the main bonding is achieved by the surface tack rather than be a wet contact with the flooring) where the tack level is reduced considerably as temperatures decrease.
Similarly, high humidity can result in a thin moisture film on the adhesive affecting its adhesion to the floorcovering. Open times and bonding times quoted go right out of the window and the installer has to ‘guess’ the best time to lay. Take the guesswork out and get conditions right first.
Next month I will discuss cold weather temperatures and floorcoverings.
Martin Cummins is Ultra Floor technical sales manager
This article has been reproduced from the Contract Flooring Journal website. You can find them at www.contractflooringjournal.co.uk.