Springy floors, sagging lintels and walls moving excessively in high winds should be problems of the past with the introduction of Amendment 2 to NZS 3604:1999 Timber framed buildings. NZS 3604 provides practical guidance on how to design and build houses to meet the requirements of the Building Code.
The amendment introduces new timber grades so designers can now choose to use higher grades than No 1 framing. The allowed spans and spacings for No 1 framing have been reduced because of evidence that some of the pine being produced has significantly lower strength and stiffness than was previously assumed.
The higher grades allow greater spans and spacings, as they have higher strength and stiffness. “Standards NZ strongly recommends that designers start using this amendment immediately as we believe houses built to the existing Standard may not perform as well as they should,” Standards NZ general manager marketing Grant Thomas says.
“Designers and builders can be confident that using this amendment will result in better quality houses, fewer complaints from home owners and less chance of call backs.” Designers will need to ensure they have clearly specified which grade they are designing to, and builders need to ensure they are using the grade of timber specified.
Timber merchants will not necessarily stock all grades, so designers should check before specifying. “Until the Department of Building and Housing has made its decision about citing this amendment, it will need to be treated as an Alternative Solution,” Mr Thomas says. “However, because the amended Standard is more conservative than the existing Standard, we expect territorial authorities (councils) will have no problem accepting the use of this amendment.”
To order a copy of the amendment call Standards New Zealand on 0800 782 632 or go to www.standards.co.nz.