Amendment 7 to the Compliance Document for Building Code Clause B1 Structure
The Department of Building and Housing has cited two important amendments to New Zealand Standards 3603 and 3604 about framing timber.
Amended timber Standards
The B1 Compliance Document no cites Amendment 4 to NZS 3603: 1993 Timber Structures Standard
and Amendment 2 to NZS 3604: 1999 Timber Framed Buildings.
Amendment 4 to NZS 3603 introduces and provides the engineering properties for new verified timber, namely VSG and MSG grades. It also down-rates the properties of unverified visually graded timber (no. 1 framing). Further, Amendment 4 requires that VSG and MSG timber be verified in accordance with the provisions of NZS 3622: 2004 Verification of Timber Properties.
Amendment 2 to NZS 3604 is a direct consequence of Amendment 4 to NZS 3603. It amends the tables and design information in NZS 3604 to account for the new VSG and MSG grades, and the revised properties of no. 1 framing.
The Department’s citing of Amendment 4 to NZS 3604 is subject to a modifi cation to clarify that the initial grading for MSG timber is based on joint Standard AS/NZS 1748: 1997, not on the 2006 version of the joint Standard released in February this year.
The differences between the two versions of the Standard are significant. The Department considers the 1997 version of the Standard must be retained, pending a full review of the differences.
Amendment 4 to NZS 3603 and Amendment 2 to NZS 3604 were published by Standards New Zealand in March 2005 and June 2006 respectively. The Department’s role is to ensure any changes to a Standard fit the performance requirements of the Building Code, and to ensure no unintended consequences. The Department has worked through a number of issues associated with the revised Standard, and engaged with industry in making its decision.
Citing the amended timber Standards in the B1 Compliance Document is subject to a transition
period, and does not become effective until 1 April 2007.
This introductory period gives further time for timber millers to put in place the necessary systems should they wish to produce verified timber. During this time, the building industry at large can familiarise itself with the new provisions. Building consent applicants can choose to use them as an alternative solution proposal. It is important during this transition period that designers specify clearly which version of the Standard their design is based on (NZS 3604: 1999 incorporating Amendment 1, or NZS 3604: 1999 incorporating Amendments 1 and 2), so that building consent authorities, suppliers, builders and owners understand what is required or what they are getting.
Amended concrete Standard
The amended B1 Compliance Document also updates the reference to NZS 3109: 1997 Concrete Construction to include citing Amendment 1 to the Standard. Amendment 1 relates to the supply and acceptance testing of concrete and was subject to public consultation during late 2004/early 2005. The amended Compliance Document is available on the Department’s website at www.dbh.govt.nz