Last edited 09 Apr 2021

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Modified wood


[edit] Introduction

Modified wood may not be a familiar term, but this durable building material is being used in homes, commercial and public buildings and external settings around the world. The term modified wood describes wood products which have been modified through treatment with a chemical, biological or physical agent to enhance their performance. This can increase its durability, making it suitable for uses such as external cladding, decking, outdoor furniture and so on.

Modified wood can also provide extra strength, resistance to fungi and rot, and is indigestible to termites. It retains the warmth that traditional wood products contribute to harsh exteriors or features made from stone, concrete, brick or steel.

The science behind modified wood has enabled it to break into markets that were previously untouched by the timber market, lending itself to unlikely projects such as canal lining, a penguin bridge in an aquarium and an external climbing wall.

The most common species of wood used in the modifying process are radiata pine, ash, sycamore and poplar.

[edit] Examples

Accoya creates a durable, non-toxic, dimensionally-stable material through the chemical modifying of plantation grown softwood such as radiata pine. It is mostly used for external cladding and wood siding, external decking and joinery.

Norway-based Kebony manufactures a sustainable and durable version of modified wood, also from species such as pine, replicating the characteristics of hardwood. It is mostly used for decking and cladding but has also been used for swimming pools, at seaside properties and in countries facing harsh weather conditions.

ThermoWood by Metsa Wood is produced by heat treating Finnish grown pine and spruce to temperatures in excess of 200 degrees centigrade. During the heat treatment, chemical and structural changes occur within the timber which alter and improve some of its basic characteristics. The resulting product is a more durable and stable timber, an ideal cladding material for use in exposed areas.

Tricoya, a product made by Medite Smartply, is a more durable and stable version of the traditional MDF panel. Tricoya can be cut, painted and wrapped without compromising its durability and stability. It is mostly used on door skins and door panels, façade panelling, trim, fascias and soffits.

British-based Brimstone is created from fast-growing hardwoods such as ash, sycamore and poplar which are grown in Britain. It is made differently to other modified timber as it uses wood thermal modification technology, meaning that it is super-heated in a controlled, oxygen-depleted environment. This creates a stable and durable product, ideal for external cladding, decking and outdoor furniture.

The Shou Sugi Ban method produces charred versions of Accoya, Kebony and Yukari cladding – a modern form of the ancient Japanese art of charring wood. The traditional craftmanship is combined with modern techniques to ensure the wood is charred evenly. This creates a fire-retardant carbon layer and a striking aesthetic.

[edit] Products for the circular economy

Modified wood can be a sustainable product, locking in carbon and contributing to the circular economy with most modified wood products using cradle to cradle design.

This was the reason that Bangaroo House, a three-storey restaurant project in Sydney, Australia, chose Accoya modified wood. Sustainability was at the heart of the project and combined with Shou Sugi Ban, the outcome is a stunning piece of architecture. Should it ever need to be deconstructed, the modified wood can be recycled or reused, creating zero waste.

In its recent report “The Future of Sustainability in Design: Rising Trends in 2018 and beyond”, Kebony looks at smarter wood products and how modified wood has impressive longevity. Kebony states that “the desire to create more environmentally-friendly structures has naturally been affecting not just how homes or commercial building are designed, but also has prompted evolution in build materials themselves.”

[edit] Comfort

Alongside modified wood’s sustainable benefits are the health and wellbeing advantages. Wood is renowned for its calming qualities, a decreased perception of stress, a decrease in blood pressure, improved air quality and generally a heightened feeling of comfort. Modified wood is also non-toxic, making it popular in nursery and school settings.

Modified timber has a dedicated chapter in Peter Wilson’s book, The Modern Timber House in the UK, New Paradigms and Technologies, published by Wood for Good in 2017.

--Wood for Good

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