Kebony, Accoya, Thermowood and Engineered Alternatives to Tropical Hardwoods

I’ve recently been doing a project that’s needed a hard, durable and dimensionally stable wood. Traditionally, tropical hardwoods have been used for projects like these, but is there not an alternative that doesn’t destroy the rainforests?

Hacking down forests and not replacing them causes the extinction of species (tropical rainforests are home to half of all species), the destruction of ecosystems (which provide clothes, fuel, timber, medicine and shelter to 300m people). Oh, and climate change, of course.

Wood is a great material – it’s recyclable, natural, waste and energy efficient, biodegradable, non-toxic, strong and beautiful. We don’t need to feel that we can’t use it because of deforestation as there are alternatives to destroying rainforest.

One solution is to ensure that the forests from which the timber comes are replanted (“sustainably managed”). The Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC) are two of the best established certification organisations. Their logo on a product is a sure sign that buying that product is not causing deforestation. Many more people have heard of these organisations now but still few realise that there are hardwoods with the certification. Some timber suppliers such as Timbmet specialise in supplying certified timber, offering certified Iroko, Meranti, Sapele and Red Grandis amongst others.

The second solution is to treat softwoods so that they become as hard and durable as hardwoods (or even harder and more durable).


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Kebony structure. Image: www.worldarchitecturenews.com

Kebony is a product made by treating FSC or PEFC certified softwoods with furfuryl alcohol made from biological waste materials. Under pressure and heat, the fluid penetrates the cell walls of the structure and polymerises the material.

The end product aesthetically resembles Teak, Ipé, Mahogany and other tropical varieties of wood but if left untreated outside develops a silver grey patina. It is commonly used in architectural cladding and has increased dimensional stability, durability and hardness compared to untreated softwood. Kebony has the official Nordic eco-label, the Swan eco-label. It is available made from Maple, Scots Pine and Southern Yellow Pine.


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Black Accoya on a church in The Hague, Holland. Image: www.accoya.com

Accoya, by Accsys Technologies is a similar product. It is also made from FSC or PEFC certified softwoods, but treated using an acetylisation process. Wood contains hydroxyl groups which absorb and release water, causing the wood to expand and contract. When these groups are converted to acetyl groups, swelling and shrinking are reduced by 75%. Hydroxyl groups are also believed to initiate decay, and Accoya is claimed to last 50 years above ground and 25 years in ground or fresh water. It is non-toxic, insect and UV resisant and requires being treated in outdoor scenarios to avoid turning black, although sometimes the black appearance can look great.


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Thermowood. Image: www.metsawood.com

Thermowood is a term that describes Finnish-grown, PEFC (Pan European Forest Certification) certified pine that has been heated and dried in a controlled way up to 200 degrees C. The process improves durability and stability and makes the product suitable for external cladding.


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Lyptus decking at Bury St. Edmunds Golf Club. Image: www.woodlinkuk.com

Also worth checking out is Lyptus from Woodlink, a PEFC certified Brazilian Eucalyptus used for decking. The colour variation in the finished product is particularly beautiful.

Most of these materials are being used for architectual cladding at the moment but there’s plenty of opportunity for other applications. Kebony is pushing this through their public seating concept Spine.

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Kebony Spine Public Seating. Image: www.kebony.no

If you’ve seen any other designs, please leave a comment below…