DBH Cites Amended Structural Grading Standards into the Building Code
16 September 2006
DBH Cites Amended Structural Grading
Standards into the Building Code
On 14 September 2006 the Department of Building & Housing (DBH) amended the Compliance Document B1 Structure by referencing the following amended standards:
Amendment 4 NZS 3603:1993 Timber Structures Standard.
Amendment 2 NZS 3604:1999 Timber Framed Buildings.
Amendment 1 NZS 3622:2004 Verification of Timber Properties.
The amended Compliance Document will become effective on 1 April 2007.
The amended suite of standards introduces new grades of timber that require their structural properties to be verified in accordance with the standard NZS3622.
An unverified grade (Visually graded No 1 Framing) is still allowable for use although its structural properties have been downgraded. Design tables exist for this grade in the amended NZS3604 and are the same as for MSG6 grade.
NZ S3604 includes three sets of design tables for MoE 6 (MSG6/No1 Frame), MoE 8 (VSG8/MSG8) and MoE 10 (VSG10/MSG10) grades.
What does this mean?
The amended standards will apply to building work consented on or after 1 April 2007. However the amended standards can be used up until that date as an alternative solution.
It is almost certain that all territorial authorities will readily consent to the construction of new dwellings using the new grades under the amended NZS 3604 because their provisions are more conservative than the existing acceptable solutions. Already designers are specifying the new grades.
Apart from No. 1 Frame grade, all other grades (including MSG grades) must be verified. As a part of the verification requirements, an independent third party must be appointed.
Because of this citation it is essential for all sawmillers who are looking to produce verified structural timber, and this includes treated timbers to be used as decking sub frames for example, to take steps now to comply with the verification requirements. The process to become a verified timber producer will take several months. It involves the installation of a testing machine and necessary software as well as implementation of quality assurance systems and extensive trial work. Given that the Christmas/New Year break will be occurring before 1 April 2007 it is essential that you start the ball rolling now.
Verified Timber Ltd is able to supervise all steps necessary to achieve verification status.
The Timber Preservation Council endorses Verified Timber Ltd as the programme of choice. You can contact Verified Timber Ltd on 04-471 2424 or refer to their website www.verifiedtimber.co.nz for further information.