Decking and outdoor furniture

Outdoor areas get a lot of use in New Zealand's temperate climate, and are important areas for children to play safely. Decks, steps, edgings and outdoor furniture are common features of outdoor areas in New Zealand homes. Most decking and a significant proportion of outdoor furniture in New Zealand is made from timber.

When you're choosing timber, consider using products that:

• don't need chemical treatment
• are sourced and made locally, and
• come from certified, sustainably managed forests.

Options for decking and outdoor furniture

Deck piles must be concrete or treated timber - they are in direct contact with the ground and must be durable to moisture and insect damage.

Treated pine is widely available and commonly used for decking.

Tropical hardwoods such as kwila are commonly used for outdoor furniture and are also durable alternatives to treated pine for decking. They don't require preservative. However, understanding where they come from can be a challenge.

There are other timber alternatives that provide functional, attractive options for decking, furniture and edging providing the heartwood is used:

• heartwood from plantation cypress (lawson, lusitanica, macrocarpa)
• eucalyptus (stringy bark, eastern blue gums/saligna)
• recycled hardwood (jarrah, blackbutt, ironbark).

Recycled plastic is also an option for outdoor furniture.

Toxicity, emissions and air quality issues

Treated pine is often used for deck piles and framing, and for decking. This treatment involves toxic chemicals such as chrome and arsenic which have effects on the environment and on human health. For more information about timber treatment, see Exterior building materials.

Sourcing

By making an informed decision about timber purchasing, you’ll be:

• supporting retailers, suppliers and manufacturers who have invested in sustainable management, certification programmes and improving environmental performance
• helping to protect forests and eco-systems from destruction, and helping to protect forest communities
• helping to discourage illegally logged and traded timber.

Sustainable supply

Timber - including hardwoods   is available from sustainably managed forests. For example, timbers such as pine, eucalyptus, cypress and macrocarpa can be sourced from sustainably managed plantations both from New Zealand and overseas. And hardwoods can be sourced from sustainably managed tropical rainforests which support small local communities living in the forest environment. (Trees are felled singly, cut and carried out individually allowing the eco-system to support natural regeneration of trees. Such systems are an alternative to clear-felling.)

To ensure you're buying timber from a sustainably managed forest, look out for the following certification schemes. These schemes are provided by independent organisations to certify sustainable forest management, and full traceability of timber products from forest source to end-user. This is also known as 'chain of custody'; it aims to prevent the trade of illegally sourced timber that is on-sold without proof of origin.

Ask for evidence of certification, and a chain of custody number.

Forest Stewardship Council (FSC) - this is the most well-known and reputable global scheme for certification of forest management and chain of custody. It has certified forests in 57 countries, including New Zealand. In New Zealand, evidence of certification and a chain of custody number are most likely to come from the FSC.

Tropical Forest Trust (TFT) - this organisation links producers, suppliers and buyers to create ethical supply chains for tropical timber.

Australian Forestry Standard (AFS) - this scheme provides sustainable forestry management certification for Australian forests.

Program for Endorsement of Forest Certification Schemes (PEFC) - this is an umbrella organisation for assessment of a number of forest certification schemes.

The Imported Tropical Timber Group (ITTG) - members include New Zealand timber importers, retailers and environmental NGOs, including Greenpeace. It has import standards that include certification and a requirement to import timber from sustainable sources. Not all New Zealand timber importers belong to the ITTG.

American Tree Farm System (ATFS), CAN/CSA-Z809 Sustainable Forest Management Standard (SFM) and Sustainable Forestry Initiative® (SFI) - these are overseas certification systems for American forests.  Products from these forests could reach New Zealand through a chain of custody verified process.

Efficiency and functionality

An argument against untreated timbers for decking and furniture is that they lack the required durability. However, that isn't necessarily the case. Untreated timbers may need a non-toxic preservative to improve their natural durability expectations from around 10-15 years. There are a number of oil-based products available, including all-natural ones that will provide protection for untreated timbers. Check how often they need to be applied for best effect, and to achieve the required durability standard under the Building Code. You may decide that applying a coat of oil every two or three years is a worthwhile tradeoff for not exposing yourself and your family to the chemicals in treated timber. Timber decking piles will need to be treated to Building Code requirements for timber in contact with the ground.