It has been a while since we posted about the revision of EN1912, but is time for another update.
The draft is now out for public comment until 27th December 2022. You can access the draft and comment, via free sign up to BSI’s standards development website
There are many new assignments (and you should double check the ones you care about are correct), and also some changes attempting to be clearer about growth areas. Perhaps you have some thoughts on that – and if so it would be very helpful to let the committee know.
Visual strength grading of timber is carried out according to grading rules that are usually (but do not have to be) national standards (like BS4978 for softwoods and BS5756 for temperate hardwoods). How these visual grades correspond to strength classes (assignment to a strength class) is specific to a combination of grading standard, species and timber source. EN1912 is the European Standard that lists assignments for visual grades of structural timber to strength classes.
(EN1912 does not list all the assignments for visual grades to strength classes. Assignments may also be listed in other standards or documents as long as they do not contradict EN1912. EN1912 is also limited in scope to only the strength classes that are listed in EN338 – so not covering, for example, TR26.)
EN1912 only lists assignments of visual grades to strength classes that are based on one of three things:
- Testing and calculation – written up into reports that have been approved by CEN TC124 WG2 TG1 (“TG1”) (the current standard for this is EN384, but old assignments may have been done to other standards)
- Testing and calculation a long time ago, and not having gone through TG1.
- Or have been listed on the basis of common and long-standing practice. This only applies to old assignments – added into EN1912 when it was still a new standard.
The new draft of the standard also attempts to indicate the evidence basis, although it leaves the reader to decide if the stronger basis is testing, or long standing use without problems.
EN1912 needs updating for the following reasons:
- To improve the text and make it compatible with changes to other standards (notably EN14081-1)
- To add in new visual grading assignments that were approved by TG1 since this version of EN1912 was written (and some approved before then, but were not included by mistake)
- To add in also assignments to tension strength classes, following their inclusion in EN338
- To update references to the visual grading standards
- To clarify (and better define) both species and growth areas
- To include some information about how the assignment got into EN1912
- To make some changes to how the information is tabulated to make the standard easier to use
In order to do this, CEN TC124 WG2 (“WG2”) wrote to mirror committees of the National Standards Bodies requesting an answer to three questions:
- To clarify the growth areas (timber source), where this is currently too vague.
- To give information about the evidence base for the assignment, where this is not already known by WG2
- To give up to date information about the grading standards – specifically the bibliographic details and whether there have been any changes to the standards that might affect the grading
Not all the information was provided, so some assumptions had to be made, particularly about some of the growth areas.
You should send your response via the formal standards commenting process, but you can contact Dan Ridley-Ellis if you have any other comments.