Preparation Is Key

In my opinion, it is impossible to over emphasise the importance of correct and thorough subfloor preparation.  But never one to shy away from a challenge, I’ll have a go.

For some, preparation can be the thinnest coat of cheap screed over whatever is left on the subfloor after removal of the old flooring.  Thankfully, to the majority of flooring contractors it’s a necessary and crucially important part of the flooring process on which the longevity of the installation as a whole depends.  What’s the point in laying a quality finished floor covering designed to last 10/15years or longer on a millimetre of badly mixed smoothing compound that looks like it’s been laid with a shovel?

To compound (excuse the pun) the situation, today’s market demands floor coverings that are more and more decorative.  Many vinyl products like Altro Timbersafe, mimic natural materials such as marble or timber and the effect is completely lost if the subfloor looks like the North Sea, or if every joint in the boards beneath clearly show through.

If a smoothing compound is to be used, getting the right one for the job is of course important, but just as important is the correct mixing ratio of powder to liquid, and applying it the manufacturers recommended thickness as all three greatly affect the hardness of the cured product.

Modern smoothing compounds include true self-levellers for anyone who’s not such a dab hand with a trowel. In addition, manufacturers are queuing up to offer advice or visit site to help you get the best result from their products in the hope of securing more business.

Many customer complaints arise from the misuse of latex smoothing compounds. These can be difficult to trowel flat and it can take a bit longer to achieve a finish that won’t make you seasick. These poor results are difficult to defend and it’s best to avoid them in the first place.

Latex screed can be finished to a high standard in several ways. Skill with a trowel is an obvious starting point and logically, the bigger the trowel, the fewer the marks in the finished job. Allowing the screed to set for an hour or so before wetting the trowel with water and going back over the surface with a big sweeping action is another good tip. If you catch it right, you’ll flatten the original trowel marks without leaving new ones.

Alternatively, a spiked roller passed through the wet screed not only prevents the formation of tiny craters as the screed dries, but also flattens trowel marks. This is best achieved by one man applying whilst another rolls, a method that has been used in the resin industry on self-flowing systems for many years with great success. Stoning down once the screed has hardened, though a little outdated, is also a tried and tested method.

If none of the above take your fancy, Altro manufactures a resin compound for use under vinyl flooring that dries completely matt with obvious advantages. This makes apparently good screeders, even from those whose work looks like they used the bucket to lay the screed rather than the trowel.

Another important factor which is sometimes out of the flooring contractors control due to time constraints, is how to allow sufficient curing time for the smoothing compound before the floor covering is installed.

Generally speaking, in reasonable drying conditions most smoothing compounds will take light foot traffic after a few hours and will allow the installation of floor coverings a few hours after that.  But problems can still occur if the finished floor is heavily trafficked before the smoothing compound has had time to fully cure.

Even though the flooring has been laid, the smoothing compound may still be susceptible to indentation from heavy trolleys or machinery manoeuvred into position on small wheeled trucks.   Not to mention the damage that chair legs can inflict, particularly when only two of the four are in contact beneath a ten stone sixth-former rocking back and forth on the newly installed floor covering.

And we’ve all heard the startling statistic that an eight stone woman in stilettos exerts a downward pressure of several tons per square inch on the 2mm of plastic you’ve just finished laying and are still awaiting payment for.

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