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Water In Adhesives Can Affect Wood

Jim Coulson on adhesives – Part 1
I HAVE spent a lot of time in CFJ telling you about the different types of timber and wood-based products that you might use: and I’ve also warned you about using poor quality materials and what you can do to avoid them.
This month, I will discuss some problems which might be caused by the use of particular adhesives for fixing floorcoverings onto wood-based substrates.
In some of my previous articles in CFJ, I talked about moisture content in wood; and also about how and why to use a moisture meter properly. That was in relation to potential problems connected with the moisture inherent in the wood itself; and the fact that you might need to ‘condition’ some types of flooring (especially solid hardwood ones) before they could be used without misbehaving.
But you can also cause problems by introducing moisture into your wood-based substrate – be that chipboard or plywood – during the actual floorlaying operation itself. That is because wood is ‘hygroscopic’: a fancy word which means that it will absorb moisture from elsewhere and in so doing, it will react in some way which may not be helpful.
It is not always appreciated that many adhesives – and indeed, many screeding and joint-filling compounds, too – can contain water to a greater or lesser extent. And this included water – which is there to enable the product to be applied easily and which may also help it chemically to ‘set’ – eventually has to end up somewhere, as the product (that is, the adhesive, screed, or whatever) dries out.
A lot of that water may manage to evaporate into the atmosphere, but some of it must, by the very fact of the product now being ‘trapped’ between the wood-based substrate and the floor covering, be absorbed directly into the wood. And that is where problems can occur!
Chipboard can – almost literally – ‘fall apart’ if it gets too wet; so a moisture-resistant grade is highly advisable. And solid wood can ‘warp’ if it gets too wet and then, more especially, as it dries out again. But the worst ‘culprit’ is plywood: and cheap Far-Eastern plywood at that.
Not all of it is ‘bad’ (see my previous articles on what makes a good plywood), but there is still a lot out there which will delaminate or ‘blister’ if it becomes wetted by a water-based adhesive, or by some other compound used in the floorlaying process.
So the thing to do is to look very carefully at the tin or the tub of the product you are planning to use; and see if it mentions being water-based (perhaps on an accompanying datasheet). If it is, then choose your substrate flooring material with great care: or change to a solvent-based adhesive!
Jim Coulson is Director of TFT Woodexperts, based in North Yorkshire

T: 01765 601010

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