It has come to my attention that an amendment to BS 5534 has just been pushed through, which changes the grading rules on tiling battens. As far as I am aware, there is no published evidence which supports the supposed reasons given for the change, and yet there is some serious misinformation being bandied about, which has all sorts of implications for timber used in other respects, especially structurally graded timber.
As an example of this misinformation, I quote from the website of one leading supplier of roofing battens:
“These changes essentially make batten cut from the centre of the log, a practice that has recently become more prevalent, unsuitable for manufacturing roofing battens, which should be cut from the stronger sideboard material. Centre-cut timber, when cut to small section such as roofing battens, is more prone to distortion as the stresses within the log are different. The knot characteristic and defects such as slope of grain make on-site grading practically impossible.”
As a consultant wood scientist, and a grading specialist of over 35 years’ experience, I have serious worries about the accuracy of those statements. In my experience, it is always possible to grade timber, no matter where in the log it was cut from, if the grader has been properly trained to recognise the defects. And if “centre-cut” material (however one defines that) is seriously weaker, then why is it not banned – or at least restricted – in all other appropriate timber standards, such as strength grading or scaffold boards?
This whole issue is about a “turf war” – which I do not wish to be party to – but my real concern is that wood science is being deliberately distorted in order to favour a commercial argument.
Jim Coulson
Director
Technology For Timber Ltd
