Warranties, Guarantees & Service Life

This section discusses warranties, guarantees and service life in the context of durability.

Warranties or Guarantees

A product warranty or guarantee may be given for a product or use, but they usually have a number of conditions or limitations as to when it will apply or be honoured. 

The supplier may specify installation, handling and maintenance requirements for timber products and request the proof of purchase be retained. 

Warranties may be for a period less than the overall service life of the timber product but should not be less than the guarantee for a minimum performance.

Generally a product warranty may not imply required durability unless the timeframe matches the minimum performance period of Clause B2 Durability in the NZ Building Code.

Liabilities of those offering goods and services are subject to legislation: The Consumer Guarantees Act 1993, The Fair Trading Act 1986, The Commerce Act 1986 and The Sales of Goods Act 1908.

The New Zealand Building Code Clause B2 Durability is very important in terms of performance, including requirements for a building element being ‘fit for purpose’.

Regardless of a suppliers warranty or guarantee term, any timber and wood-based building element must with normal maintenance, satisfy the minimum performance period for durability. 

The only variation would be if the intended life of the building was a lesser time than that given in Clause B2.

Minimum performance periods for timber elements are categorised as 5, 15 and 50 years. 

Structural building elements which are difficult to replace or crucial use,  or not accessible for regular maintenance,  e.g. timber framing, building poles/piles, are examples of elements which are required to be serviceable for a minimum of 50 years. 

Other building elements such as cladding and joinery (not difficult to replace or readily accessible for regular maintenance) fall within the scope of the 15 year minimum performance requirements. 

Information on specific timber species, preservative treatment levels and timber building elements can be found in NZS 3602: 2003 Timber and wood-based products for use in building.

Very few timber components used in buildings fall into the 5 year minimum durability category.

Preservative treated products complying with the preservative standards are required to carry identification of the treatment facility, preservative (type) and hazard class (preservative level). 

This may take the form of end brands or tags or be as strip brands along the length of timber products.   

Service life

Although the Clause B2 Durability states the minimum performance requirements to meet the Building Code, the service life for wood products would be expected to exceed those minimum time frames times.

Other clauses under the Building Code are also relevant to the acceptability of timber, e.g. B1 Structure, E2 External Moisture, F2 Hazardous Building Materials.