Warranties and durability of building products.
I am frequently asked if a warranty has to be for the same period as the durability period and I am often asked if a warranty is required as part of the consenting documentation.
Here is my understanding.
A warranty and compliance with B2 (durability) are different. A warranty relates to the material and is defined by the warranted condition and the time at which the warranted condition applies. Both these are set by the supplier. Typically it will cover freight defects and manufacturing faults that are obvious at time of delivery. In many ways the warranted period is academic because to claim on a warranty you have to demonstrate the "fault" at the time it applied (as defined in the warranty) and within any other requirements applied by the supplier eg prior to installation, that it applies only to the initial purchaser.
Compliance with B2 is not subject to a warranty it is a characteristic that the supplier will always be accountable for, but within the time constraints of the different laws. This is complicated. But the best analogy is the car manufacturer doing a recall because on certain models they find an air bag to be faulty. The warranty is not required nor is it restricted to the first owner.
A warranty makes good business sense especially where it comes from the NZ-based supplier. It shows the market that they stand behind the materials that supply to the market and also allows them to set any rules they wish. I don't support lengthy, "small print" warranties as in my opinion they are more about illusion that actually standing behind the product that is supplied.
As for durability and how you might establish that. I have thoughts and that will be another post (running out of words).
Finally; no a warranty is not part of the building consent documentation as it does not relate to any building code.