EN 14081-4 “Timber structures. Strength graded structural timber with rectangular cross section. Machine grading. Grading machine settings for machine controlled systems” is the standard that got too big to be a standard. The last version, now withdrawn and superseded by EN14081-1:2016 (although see here), contained machine control settings for 15 grading machines, with a total of 62 tables of settings. As of 14/11/2018 there are 35 grading machines with machine control settings and some 517 tables of settings. New machine control settings are approved twice a year by TG1 – typically adding new growth areas, new grades or new species to about a third of the machines.
It is therefore impossible to keep EN 14081-4 anything close to being up to date – and if it did contain all the settings tables that exist now it would be extremely huge and expensive. So how does anyone know what machine settings are available? Well these tables of settings (now called ITTs but in future to be known as AGRs) actually belong to the machine manufacturers, and they are the best people to ask. Notified bodies need access to all the settings tables, and to be sure they have the latest ones, so TG1 passes on sets of tables they update, to the sector group of Notified Bodies for construction products.
These tables of settings are not limited to the strength classes you can find in EN338 – since this is only a list of some general ones. For a long time there have been strength classes for other purposes – such as TR26 for trussed rafters in the UK, tension classes for glulam manufacture (predating the ones now in EN338), and bespoke grades that we have developed for British species.
Leave a Reply
You must be logged in to post a comment.