Last month, in this column in ‘What is wood science?’ John Park mentioned the handing down, through the generations, of skills and an intimate understanding of wood.
Plywood was a little different as it has come through a period from its invention by the Egyptians but before the introduction of synthetic resin adhesives when it delaminated if you breathed on it – remember tea crates? In construction circles plywood had an abysmal reputation for many years.
And then, with the aid of wood science, plywood became a much more reliable material following development of product standards and factory production control. British Standard (BS) 6566 introduced the term ‘WBP’ and BS 1088 provided the enhanced performance requirements for marine plywood.
Then European Standards (EN) arrived with the introduction of a new classification system for plywood. Alas the plywood trade did not always keep up. And, sadly, in some cases cheap started to overtake quality.
In the chapter on wood-based panels in my 2014 book “Wood in Construction: how to avoid costly mistakes” I say the very phrase that makes up the title to this piece. And I explain that the letters “WBP” used to mean – and I say “used to” very deliberately – “Weather and Boil-Proof”.
However,that designation has not been valid (and thus should no longer be in use) since BS 6566 was withdrawn almost 25 years ago, to make way for a range of ENs on plywood and other wood-based panels. And yet it seems that the whole of the timber trade – as well as many architects, specifiers and builders – cannot get out of the habit of using those letters.
The main problem (apart from the small matter of obsolescence) is that most of the people who still use those three letters have really no idea what they refer to; and so most people seem to think that they just mean something like: “a good, all-purpose plywood that won’t give me problems” – which is usually where the problems begin. That is because plywood no longer exists as ‘WBP’ – and has not existed as ‘WBP’ for a quarter of a century.
Anyone who asks for WBP, never actually gets it and so the timber trade will simply supply whatever it is that they have in stock; which then may or may not (and usually it is not) meet the intended use. The fact that we at Woodexperts see relatively few problems with plywood in buildings owes more to good luck than good judgement; or rather, good specification.
I recently had personal experience of this phenomenon, as a mere “punter” – rather than as a wood scientist – when I went to my local timber merchant (who shall remain nameless) to get some plywood for a domestic project.
I asked what types of plywood they had and I was shown some “fair faced” plywood. It actually had a label on it stating that it was EN 636-2 but the assistant said to me, “I’ve got this very nice WBP plywood”.
Not only was he using the completely wrong, not to mention obsolete, description, he obviously had no idea what that label actually meant, either. And the worrying thing is, if I had actually been intending to use the plywood outdoors (which I wasn’t), then I might have assumed – completely erroneously – that it would be fine. But EN 636-2 plywood is only intended for internal use, where there may be high humidity or a risk of occasional wetting: and it is not suitable for exterior use or in areas where it may get and remain wet.
Builders (and their trade suppliers) please take note: there is no such thing as WBP plywood!
