Issue 52 – August 2013
Imported plywoods manufactured using timber species that are unusual for New Zealand are readily available. However, when proposing to specify an imported plywood, be aware that they may not:
- meet New Zealand Building Code requirements for treatment (where treatment is required)
- comply with the standard AS/NZS 2269:2012 Plywood – Structural when used in structural applications such as flooring or bracing (has bracing performance been verified using the BRANZ P21 bracing test?)
- be manufactured from timbers that are sourced from a sustainable resource
- have a verified durability, particularly for external applications such as cladding
- incorporate glues of known performance
- be timber that is not commonly used for plywood in New Zealand (such as willow-faced plywood)
- perform as expected.
It has been brought to BRANZ's notice that these imported products may not be suitable for use under roofing membranes or asphaltic shingles – reported problems have included extensive surface checking (veneer splitting) and excessive movement. They may also perform poorly when used behind plasterboard linings.
It is also worth satisfying yourself that:
- the supplier is reputable – there is an advantage in staying with suppliers who are known and who back their products
- there is adequate and competent technical information and support for the product
- fixing and installation instructions are available and applicable to the end use and New Zealand conditions
- the product will be compatible with or suitable for use with adjacent building materials
- a warranty is available.
While these comments cover plywood, in essence, it is a cautionary tale for all imported products, and being aware of a product's provenance is critical before the product is specified and/or installed. In the plywood example, replacement of a complete roof cladding system to address the performance issues reported with the plywood will be an expensive process.
Remember the saying: 'Nobody ever made any money doing a job twice and being paid for it once.'
Summarised from BRANZ Guideline, July 2013.