Jim Coulson on specifying plywood

WHEN flooring contractors are faced with the need to overlay an old floor surface, prior to installing a high quality flooring finish, they always seem to end up asking for – or perhaps being offered – WBP plywood.

But it may come as a surprise to many, to learn that there is actually no such thing as WBP: and in fact, there probably has never been such an animal, in the world of contract flooring!

The letters WBP in themselves, stood for Weather and Boil-Proof (and not Water and Boil-Proof, as so many users of plywood seem to think!); but this was only ever a description as to how well-glued any plywood was supposed to be.

And I say ‘was’, because that description became obsolete more than a decade ago…although when dealing with many plywood stockists, even in 2012, you’d be forgiven for thinking it was still current and had some meaning to it. But no – those letters have absolutely no validity in the 21st Century!

They were meant to convey the idea that plywood, when used in any situation where there might be moisture, dampness or excessive humidity, should not fall apart – or ‘delaminate’, as the posh word for that problem, really is.

However, over the years, those three little letters have somehow come to invest plywood with almost magical properties, so that it will do virtually anything if it is called WBP: but nothing could be further from the truth.

In my not inconsiderable experience of dealing with timber and wood problems over nearly 40 years, I have almost never found a so-called WBP plywood that met the required standard; and yet I have found hundreds of examples where so-called WBP plywood failed in service by delaminating.

So what should we ask for now, I hear you ask, if WBP doesn’t exist? And the answer is: plywood that has at least the glue bond characteristics of the European Standard EN 314, Class 3 (that is, suitable for Exterior use – or a similarly wet/moist/humid environment).

However, there is more – much more – to specifying plywood, than merely asking for Class 3 Exterior to EN 314.
And in my next article, I will outline one or two other characteristics that you should consider asking for, next time you specify plywood for overlayment… .

Jim Coulson, director: TFT Woodexperts, Ripon, North Yorkshire