Modified wood stretches the boundaries of what wood in its natural state is capable of doing. The U.S.D.A.’s National Forest Service Library defines modified wood as “wood that is processed by chemical treatment, compression, or other means, with or without heat, to impart permanent properties quite different from those of the original wood.”
Thermally modified wood is redefining the properties, features and applications of natural wood in a wide spectrum of residential and commercial applications. Industry innovators are using ground-breaking technology to take wood products into previously uncharted territory, giving pine, spruce and other softwood timbers the super-strength powers of traditional hardwoods like oak and maple and exotic hardwoods like teak and ipe.
The last decade has seen a significant increase in the demand for modified wood. Increased interest comes from the desire to increase the decay resistance and longevity of timbers from Scots pine, beech, southern yellow pine, ash, birch, alder, radiata and many others.
Increasing the lifespan of timbers normally requires a preservative, but wood modification technology does much more than that. It imbues wood with other welcome changes like dimensional stability and maximum hardness.
The Process of Making Modified Wood
There are three main processes for making modified wood:
- Heat Treatment – Depending on the wood species, the heat-treating process warms the wood from 185 degrees to 212 degrees Centigrade. Also known as thermal modification, the process makes common woods decay-resistance and heightens the natural color to a richer hue that goes all the way through the board’s thickness.
- Acetylation – Substances known as free hydroxyls are present in all woods, naturally releasing and absorbing water in response to changes in the weather. The process of acetylation changes the free hydroxyls into acetyl groups. An acetyl group is a small molecule made of two carbon atoms, three hydrogen atoms, and one oxygen atom. In this new form, acetyl groups alter the original properties of the wood, making it more durable and dimensionally stable.
- Polymer Grafting – Polymers are formed when a single molecule called a “monomer” are able to join with at least two other monomers, a process known as polymerization. When this process is used on wood, it provides a locked-in structure to the wood’s cell walls. Polymerization adds many in-demand features and benefits for timber used in construction, including durability, strength, dimensional stability and resistance to the destructive effects of insects and microorganisms.
Modified Wood Is Good for the Environment
The demand for eco-friendly modified woods is being shaped by growing concerns about global warming, the ongoing decimation of the world’s hardwood forests, and the reckless harvesting of both soft- and hardwood forests. The green design and construction movements are gaining momentum as property developers and builders respond to the environmental concerns of investors, businesses, future buyers and homeowners.
Kebonization Process of Modifying Wood
One of the leading paradigm-shifting innovators is Kebony®, an eco-friendly Norwegian manufacturer and global marketer of patented, modified wood products for outdoor applications such as decks, docks, marinas, outdoor structures and cladding for residential and commercial business exteriors.
Kebony uses polymer grafting to enhance the properties of sustainable woods with their patented “kebonization” process:
First, the wood is impregnated (soaked) in furfuryl alcohol, a natural bio-liquid byproduct of agricultural crop waste. Next, the wood goes through the curing (heating) process. During this stage, polymerization occurs. The furfuryl alcohol forms polymers that permanently lock into the cell walls of the wood, making them 50% thicker. These stable polymers won’t disintegrate or leak out of the wood. The end result of the process is Kebony®, modified wood with a wide array of cutting-edge benefits and features.
Benefits of Eco-Friendly Modified Wood like Kebony
- Real Wood – Eco-friendly modified wood is real wood—only better. The polymerization process enhances and strengthens cell structure.
- Refined & Beautiful – Modified wood may come in a choice of options: a smooth and silky look or a rustic and knotty look. Some modified woods, like Kebony, have a deep brown color that gradually turns to a beautiful silver-grey patina over time. The color change has no negative effect on decay resistance or other properties of the wood.
- Maximum Hardness – Hardness levels of some modified woods match or surpass the levels of the best hardwoods.
- Outstanding Stability – The dimensional stability of eco-friendly modified wood can significantly reduce normal swelling and shrinkage caused by relative humidity by 40 to 60 percent.
- Guaranteed Long Life – Modified wood products are ideal for outdoor applications, regardless of harsh, freezing winters or record-breaking summers of triple-digit heat. Some eco-friendly manufacturers offer an outdoor lifetime warranty of 20 or 30 years.
- Low Maintenance – Traditional treated wood for decks requires annual maintenance like staining, waterproofing and sealing to keep it looking good and lengthen its lifespan. However, modified wood like Kebony®, for example, needs nothing beyond normal cleaning to maintain its look and structural integrity.
- High Resistance – One of modified woods’ main goal has always been to increase the longevity of the wood by protecting against fungi, rot, insects and other wood-destroying micro-organisms. Technology within this category has come so far, that some manufacturers offer a 20+ year guarantee.
- Safe & Toxin-Free – The most dedicated eco-friendly manufacturers don’t use toxins or harmful impregnation substances in their modification process. The end products resist splintering and don’t contain toxins or chemicals. With these stellar safety benefits, it’s not surprising that these particular modified wood products are often used for residential as well as school decks where kids have frequent contact with the wood.
- Eco-Friendly – Top modified wood makers use eco-friendly modification processes that don’t use harmful or toxic chemicals as well as maintain and support responsibly forestry practices. Their products will display “environment friendly” labels like the Nordic Council of Ministers and other environmentally conscious organizations around the world.
- Sustainable Sources – Raw materials can be sourced from many different outlets, however not all companies and properties are managed through sustainable practices, making companies who do chose to operate sustainably from harvest to the end result even more admirable. For example, manufacturers like Kebony® have many products that are FSC® certified by the Forest Stewardship Council. The certification shows manufacturers and their sources uphold principles and criteria that observe the highest social and environmental benefits and considerations.
The Beautiful Diversity of Eco-Friendly Modified Wood
Stunning examples of modified wood applications can be found in the middle of the largest cities, in remote locations and on the seashores of oceans, lakes and rivers:
Commercial/Civic Uses of Modified Wood
- Google Fiber Office, Atlanta, Georgia
One of Google Fiber's newest offices in Atlanta included the construction of a spacious and inviting public outdoor area, built on beautiful, low-maintenance clear decking.
- Hunter’s Point South Waterfront Park, Long Island City, New York
The city park’s elevated wooden boardwalk features sleek, durable modified wood decking. The park is the first step in the rejuvenation of this old neighborhood on the Queens side of the East River.
- Marina at Harbor Shores of St. Joseph, Michigan
The developer wanted a marina that was beautiful and tough enough to handle harsh weather of the Great Lakes coast. “We have designed more than 300 marinas around the world utilizing nearly every type of decking material available, and Kebony® wood stands out as one of the best,” said Greg Weykamp, Principal at Edgewater Resources, the project designer and developer. “Since installing nearly 12,000 square feet of Kebony decking two years ago at a public boardwalk and marina south of Chicago, not a single piece of Kebony has needed to be replaced for any reason.”
- Popular Orlando, Florida Theme Park
The natural, exotic beauty of modified wood as it weathers was a perfect match for the park’s theme. The product’s environmental sustainability was a major selling point for the outdoor arena seating.
Residential Uses of Thermally Modified Wood Siding & Decking
Houses around the world are incorporating the beauty of green architecture and design with eye-catching modified wood as exterior decking and cladding. Rustic modern exteriors have become popular, artfully blending natural wood with other materials like glass and metal. In contrast, traditionalists love the look of real and natural modified wood.
Homeowners are loving the versatility of modified wood decking and cladding which can be installed horizontally, vertically or at angles to showcase the home’s unique design and personality. Design options include, but certainly are not limited to: changing angles on the same structure, using modified wood as accent lines on a predominantly glass facade, cladding around windows to showcase them, and modified wood with hues that blend in with the home’s natural environment.
Imagine the Endless Possibilities of Modified Wood
As an architect, developer, builder or homebuyer, you may be attracted to modified wood for any or all of its many benefits. Now that you know much more about modified wood, you can look past traditional designs and materials and free your mind to the endless possibilities of the true beauty of environmentally responsible modified wood.