Standard Operating Procedures (SOP's) and specialty timbers
The key aspect to ensure both grading systems are compliant is the verification process. Both grading systems are subject to the same rules and grade acceptance criteria as set out in the Verification Standard NZS 3622:2004.
The verification process described in NZS 3622:2004 is an output control system, which means that timber is continuously taken from production and tested for stiffness and bending strength by the producer. Independent auditing also takes place. The Verification Standard is based on random sampling and statistical analysis to ensure the population of timber within a stress grade is meeting the requirements of the grade. Essentially, each grade has an average and minimum stiffness rating (Modulus of Elasticity).
WPA, TIF & DBH have put together new “Standard Operating Procedures (SOPs)” for timber treatment and grading. The SOPs are part of a proposed new Timber Quality Scheme and set out requirements for all sawmills, plants & auditors producing structural timber in New Zealand.
The pilot scheme can be seen here and the Timber Grading SOP document is here
These procedures are suited for only larger operations producing radiata pine and Douglas fir and effectively shut out specialty timbers from the structural timber market.
NZFFA's respone to the Timber Grading SOP document, dated 17/5/2011 is here.
"The purpose of the SOPs is to give timber users, the public and the DBH confidence that timber used in houses has the same quality, no matter who is producing it. In other words, they can trust that it meets the branded hazard class and grade."
"The purpose of the Timber Quality Scheme is to implement and operate a system which provides assurance to timber users, the public (consumers) and the DBH that structural timber used in building and housing meets the required quality standards, is safe to use, fit for purpose and has been produced in a way that ensures the safety of people and the environment has been protected."