Solving Sticky Situations

Well, the yuletide season has now passed with its usual mix of office parties, family get-togethers, over indulgence and presents courtesy of the annual visit by Father Christmas. And now, with Christmas becoming just a memory, New Year’s resolutions have started to kick in and most of us by now will have started to turn our thoughts back towards the world of work.

But the season’s festivities and traditions did get me thinking about other firmly held beliefs, age old customs and habits, including those in the world of flooring.

A common one is the old chestnut that all power floated subfloors have to be latexed before new, contemporary flooring can be applied. Why? Generally speaking, provided a concrete floor has been properly laid and finished and is dry, it provides a perfect surface for the direct bonding of most new floor coverings.

Often when latex is applied to such a surface it’s microscopically thin, a scratch coat perhaps 1mm thick at best.  The problem here is that moisture from any new flooring adhesive which is subsequently applied has nowhere to go as there is insufficient depth of latex to absorb the liquid. The result can be de-bonding of the “membrane” of latex and failure of the entire flooring system.

If latex screed is to be applied to a power floated floor slab for some reason - perhaps if a surface damp proof membrane is to be incorporated - then it must be at the screed manufacturer’s recommended thickness of a minimum 3mm. That thickness hasn’t been decided on simply to sell more latex; it has come about from years of research into flooring problems and failures.

I don’t believe that the majority of flooring contractors advise the use of latex in this situation simply to make more money; like going to bed on Christmas Eve hoping to wake up to presents in the morning, it’s just something they’ve always done.

In addition to the problem where moisture from the adhesive can cause the thin screed to de-bond from the subfloor, in order to get the latex down thinly enough, often more liquid than the recommended amount has to be mixed with the powder. This results in a weak finished product further adding to the potential for failure.

Some contractors believe that latex screed is needed in this situation to provide the adhesive with a key, but this is not the case with many modern adhesives. Pressure sensitive polyurethane and epoxy adhesives can all be used to bond many contemporary floor coverings straight on to well laid power floated concrete and other smooth subfloors such as asphalt and terrazzo without the need for a latex screed. As well as removing the chance for unsightly trowel marks spoiling the finished article, this has the added benefits of saving time, effort and money.

This article first appeared in the January 2008 edition of the CFJ.