Some Specifiers Wet Behind The Ears
My four previous articles in CFJ (December 2012 – March 2013) were all about plywood.
I gave you advice on which sorts of plywood to use (and which wrongly-described plywood you should avoid!).
This month I want to give you some basic, but nonetheless essential, advice on how to avoid problems with wood-based flooring products.
The most important thing to understand about timber is its reaction to moisture. By that, I don’t just mean avoiding spilling water on it: but avoiding using it (where possible) in areas of high – or low – humidity.
Wood is a ‘hygroscopic’ material – that is, it will actively absorb or lose water molecules within its cellular structure, depending upon its own inherent moisture content and the dampness or otherwise of its surroundings.
Wood is not ‘unstable’ – it simply responds to its surroundings and therefore it needs to be understood that wood products will react to the conditions in which they are used.
Using wood at relatively high moisture contents (equivalent to ‘outdoor’ or air-dried conditions) will result in shrinkage: and that’s why softwood floorboards are typically cramped-up tightly when being fixed, so that gapping is minimised.
But do that with a solid hardwood floor that has been kiln-dried to a very low level of moisture (hardwood flooring from the USA is typically dried down to below 7%), and you will get ‘humping’ as the floor expands back up to a normal level for our room conditions.
In my work as a consultant, about 50% of the problems I see are as a result of specifiers or users not understanding the concept of moisture content in wood.
If you see something that is described as ‘kiln dried’ or ‘seasoned’ – then that’s about as much use as if it were to be described as ‘tree wood’.
Just as you need to know the species of wood you are using, so you also need to know its precise moisture content.
Otherwise, how can you know which way it will react, when it is in the situation where it’s to be used?
Unless there is a numerical value attached to the timber’s specification (15%; 7%; 10% etc) you don’t really know anything about it. And – by the way – you ought to have a moisture meter! I will talk about the use of those gadgets in my next article.
Jim Coulson is the director of TFT Woodexperts in North Yorkshire
T: 01765 601010
CORRECTION: The headline over the article by Jim Coulson in the February issue of CFJ wrongly reflected the subject matter which was on the surface appearance of plywood. The caption under the photograph should have read: An example of a veneer patch on ‘improved face’ plywood which could telegraph through sensitive floor finishes.
This article has been reproduced from the Contract Flooring Journal website. You can find them at www.contractflooringjournal.co.uk.