Designation of Structural Timber
20 September 2010
In 2006, NZS3603 Timber Structures, was amended to introduce new grades for structural timber. The new grades, which replaced No1 Framing, were;
• Visually stress graded (VSG) 8 and 10
• Machine stress graded (MSG) 6, 8, 10, 12 and 15
• Green (G) 8, for timber to be used in a green state and verified to green properties equivalent to VSG/MSG 8
All these grades were to be verified for their structural properties under the verification standard NZS3622:2004. The verification method and pass criteria, which is used by all Verified Timber producers were to be the same for both VSG and MSG timber.
No1 Framing has continued to available and used as an unverified grade with assigned values equivalent to MSG 6.
Following on from discussions involving timber producer, stockist and user groups over the past 18 months under the auspices of DBH, it is proposed that the differentiation between visually and machine graded timber will be discontinued. Given that there is no difference in the properties of VSG and MSG timber graded to the same values and that they are verified in the same manner, there is no need to continue the distinction.
It is proposed and it is highly likely, that all verified structural timber will be designated SG, as in SG 6, 8, 10, 12 and 15. This will be reflected in compliance documents and in the revised NZS3604 due to be published shortly.