Toxin-free decks

Avoid toxic treated timbers and endangered woods when building your deck at home.

Healthy homes: If you're building a deck take a pass on toxic treated timbers and endangered hardwoods and check out these more sustainable options.

Earlier this year, Element reported on the environmental and health risks associated with exposure to Copper Chrome Arsenic (CCA) treated timber. Despite the concerns, New Zealand continues to be the highest users of the preservative per capita.

Alternatively, the demand for untreated durable hardwood means that non-renewable species like New Guinea's kwila are being driven to deforestation. Kwila takes 75 to 80 years to reach commercial size and 83% of the kwila forests in New Guinea have been logged or are planned to be. Greenpeace estimates that at least $15-20 million of Kwila, in decking and outdoor furniture, is imported here every year.

The good news is that some New Zealand companies are responding to the demands of the increasingly eco-conscious DIY deck builder and making it easy to eschew the risky or non-sustainable alternatives.

For those keen on a traditional aesthetic, New Zealand company Abodo (abodo.co.nz) provides a range of renewable timber products both certified by the Forestry Stewardship Council (FSC) and guaranteed against decay and termite attack for 30 years.

Abodo's Element Sand+ Decking range manufactures North Island-grown FSC certified radiata pine and douglas fir slats. A copper-based wood preservative, Alkaline Copper Quaternary (ACQ), is set into the wood at a high temperature to reduce any risk of leakage into the environment. ACQ is free from the arsenic and chrome found in exterior wood preservatives like CCA but still meets New Zealand building code requirements.

Abodo also endorses an alternative waste-management programme for CCA-treated timber, concerned that 90% of the preservative's arsenic is released into the atmosphere when burnt. Abodo has teamed up with Green Gorilla (greengorilla.co.nz) which turns old treated timber into carbon-neutral fuel.

Bamboo, well known to be one of the world's most renewable plant sources, offers another option. Enspire Bamboo (enspirebamboo.com) makes FSC-certified, 25-year-warranted, non-bleeding and non-toxic bamboo decking. Alternatively, composite decking is an option for those looking to build an eco-conscious deck with minimal maintenance.

Composite slats are made up of a mix of recycled wood fibres and recycled UV resistant high-density polyethylene or consumer plastics, like plastic bags. Australian owned Ecologix (ekologix.co.nz) manufactures a fully recyclable composite decking made up of 50% sustainable ground bamboo, 40% recycled high-density polyethylene or consumer plastics and 10% UV stabilisers. Their slats come in set 5.4m lengths.

Outdure's Eco-Decking (outdure.com) is made from equal parts reclaimed wood and reclaimed plastic, sourced from the landfills of industrial manufacturers.

Hybrideck ecodecking (hybrideck.co.nz) composite ?is made up of 60% recycled timber and only 30% ?recycled plastic. Hybrideck says that the smaller ratio of plastic to wood in their product means that it is less likely to expand and contract in New Zealand's particularly harsh UV conditions. The company proudly boasts no formaldehyde or other harmful treatment in the manufacturing of their product. As Outdure warns, consumers should not necessarily associate composite decking with sustainability.

Shop around as some manufacturers use virgin plastics or ?only a portion of reclaimed or FSC certified wood.

FSC and PEFC certified green wood
The difference between The Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification Schemes (PEFC) is that FSC is a global standard managed by parties outside the industry whereas PEFC is an umbrella group originally set up by members within the pulp and paper industry. PEFC adopts the national schemes and standards from each country with the aim of making forest certification easier and more applicable to different types of forests.

FSC is the most credible forest certification system, endorsed by environmental organisations such as Greenpeace and WWF and by the Green Building Rating Systems of the Green Building Councils of New Zealand, Australia, South Africa, UK and USA. The FSC mark ensures that wood has been sustainably harvested and that it is from "environmentally appropriate, socially beneficial and economically viable sources."

If a product is PEFC certified in an emerging market like Indonesia, where more than one million hectares of rainforest is cleared every year, it might not satisfy the more stringent standards of a country like New Zealand.

Conventional timber finishes for wood decks contain volatile organic compounds (VOCs), which are the petroleum-based solvents that evaporate from the coating while it is drying. These compounds, which can make up 50% of an oil-based timber finish, are the unpleasant solvent fumes that contribute to air pollution. Water-based timber finishes from companies such as Intergrain (intergrain.co.nz) have a very low solvent level. Therefore using water-based timber finishes is a far more environmentally responsible option than using a solvent-based equivalent.

Like what you see? For weekly Element news sign up to our newsletter.
We're also on facebook and Twitter.