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Subfloor Prep

Martin Cummins on subfloor preparation

THIS is a surprising title for an article for the UK flooring market, you may think. What I am really saying is that the Europeans (generally) and us have very different working practices when it comes to construction projects and more specifically, flooring projects.

The main differences with subfloor preparation are the timeframes allowed on projects. In Europe there is apparently no call at all for bag and bottle smoothing compounds, which are still the main choice for UK fitters. Also, they have little use for surface DPMs, again something we regularly use in the UK.

So what do they do differently? Firstly, they spend more time on preparing floors before laying new coverings. Rather than our ‘get in, rip up, smooth and lay’ approach they lean more towards mechanical preparation to get the subfloor back to a sound strong base.

There is no ‘layer upon layer’ approach and therefore less concern about adhesion to previous adhesive residues or floorcoverings. Also returning to a sound strong base means fewer concerns about laying hard over soft products. And as a consequence there is no need to use bag and bottle type products which are generally lower strength, strong adhesion systems.

Their allowance for new build projects to dry out thoroughly means that the 75%RH level of dryness we recommend is not an issue. Their subfloors are generally dry by the time the flooring contractor is required to install his materials so again no DPM is required. Also, if no DPM is required, there is no reason to pre-smooth. So again no need for bag and bottle products.

Instead they utilise water mix smoothing compounds. Every major UK manufacturer now has water mix smoothing compounds in their portfolio so here are a few basic guidelines to getting the best from them:

1. Prepare the floor: This means getting old adhesives, old smoothing compounds and any contamination off the floor on refurbishment projects. There are some fantastic subfloor preparation companies out there who will take care of all these needs to leave you with the task of applying the materials. This is highly advisable on larger projects;

2. Prepare the floor…haven’t I said this already?: Once your initial mechanical prep has been taken care of, make sure you follow the manufacturer’s instructions with regard to priming whether it be a bonding primer or a primer to reduce absorbency and enhance the handling characteristics. This is a key process that should not be ignored.

3. Read the bag: Check the product supplied or the one you purchased if it is suitable for use where you are using it. Can it be used over that asphalt? Is it suitable over those undertile heating cables?

4. Read the bag: What level of water is required? What flow rate is needed when pumping? Have you got the recommended flow test kit? Follow these recommendations. Adding extra water to give greater fluidity really does not benefit the products and can ultimately result in failures.

When carrying out pumping applications it is worthwhile mixing up a unit in the normal manner (i.e. bucket and mechanical whisk) and measuring the flow using your flow tube and using this to ensure that comes out of the end of your hose is at the correct flow rate. Make sure the water supply is cool water not warm water.

5. Keep other trades out of the way: The handling characteristics of the water mix products is usually very good and the real benefits are that you can get an exceptional finish, ready for laying even the thinnest of vinyls, provided of course, you can control your areas!

6. Use a spikey roller: This is a real boon with water mix products where their use to marry in wet edges from unit to unit. It can enable you to achieve a glass like surface. Make sure the spike levels are sufficient to prevent drag through in the compound. This is especially important when thicker applications of smoothing compound are required.

So use the water mix products correctly for an appropriate application and you will find that the Europeans may have the right approach.

Unfortunately, it will be a long time before our building and construction industry realises that the profession that is ‘contract flooring’ gets the time and consideration it deserves to achieve first class installations time after time. Meanwhile, we will supply the bag and bottles to get the job done but, if appropriate, it is definitely worth considering a water mix product.

Here’s a word of caution, however! Don’t just look for the cheaper options. The fact that there is no bottle of polymer means that the bag itself needs to have the important ingredients which costs money.

The flip side is that there are environmental benefits from not having a plastic bottle which is something that will benefit everyone in the supply chain.

Martin Cummins is Ultra Floor technical sales manager

T: 01827 871871

This article has been reproduced from the Contract Flooring Journal website. You can find them at