What Does Modified Wood Mean?

You hear the phrase ‘modified wood’ bandied around a lot these days, so what does it actually mean? If you are working in the timber industry, or as a carpenter, builder or joiner, it is important that you understand the materials with which you are working.

The definition of modified wood is “wood which has been treated with a chemical, biological or physical agent to enhance its performance”. It is a durable building material that is being used around the world for domestic, commercial and public buildings, internally and externally. The modification process that the wood products undergo is completed in a treatment using a chemical, biological or physical agent. It often means that the wood can be used externally, for cladding or decking, for example. Or the modification process makes the wood stronger, more resistant to rot and fungi, or indigestible for termites. This has meant that wood has started to be used in building structures like canal lining, a penguin bridge in an aquarium and an external climbing wall. These are all structures where previously wood would not have performed as well in its natural state. “The most common species of wood used in the modifying process are radiata pine, ash, sycamore and poplar”.

Accoya

Accoya is the name most people associate with modified wood as it has become the timber industry equivalent of a household name in terms of modified woods. It is a chemically modified wood (usually radiata pine), which is non-toxic, highly stable and very durable. It is often used externally for cladding, decking or joinery. Organowood is another chemically modified wood, like Accoya. Organowood has been modified with the attachment of protective silicon compounds to the wood fibres. This means it is rot resistant after treatment.

Thermo modified wood

Physically modified woods such as Thermowood® are created by heat treating Scandinavian grown Pine or spruce. They are heated to temperatures of over 200 degrees centigrade, which alters the chemical structure of the timber. This makes it more durable and stable than non-modified pine or spruce. It is ideal for cladding.

The process of treating wood with fire to enhance its properties dates back a long time. Shou Sugi Ban is an ancient Japanese method which produces charred versions of Accoya, Kebony and Yukari cladding – as well as the standard Cedar, Douglas Fir and Larch cladding. The wood is charred evenly to create a visually arresting appearance as well as making the wood fire-retardant and more durable. Clearly the process of modifying wood is not a new idea. The Japanese recognised the enormous potential of modifying wood through fire centuries ago.

Incredible opportunities

Today in the Western world, wes are only just waking up to the huge potential in modifying wood through different processes. @usfs_r9 recently picked up on the big news on the incredible opportunities that modified wood offers: “Through a .@ForestService Wood Innovations Program grant, NRRI constructed a boardwalk using eastern larch killed by native bark beetles, and showcased an innovative heat-treatment process”. We are sure that we will soon see plenty more good news stories singing the praises of modified wood.

Find out more about modified wood and different types of timber, as well as eco-friendly sustainable timber by exploring our site today.

Image: GCapture / Shutterstock.com

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What does modified wood mean

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Our timber experts have years of experience and will be able to match the perfect species to your project, as well as provide a quote for sustainable timber at highly competitive prices.

Frequently asked questions

Do you supply timber for domestic uses?

Yes, we supply timber for domestic applications as well as commercial and public constructions. From garden decking to shed cladding, we will be happy to supply smaller deliveries for home use.

Is your timber FSC-certified?

Yes, all timber we supply is FSC or PEFC certified and sourced from independently verified responsibly managed forests. If we can’t find your request in FSC/PEFC certified timber we’ll suggest an alternative that is certified or clearly note that the offer is minimum EUTR.

Where does EcoChoice deliver to?

EcoChoice delivers to construction sites, warehouses and homes across the UK, as long as there’s access and unloading for our trucks.

What are the best timber species for exterior use?

There are many different timber species suitable for exterior use and which is the best for your project depends on your requirements. In general, though, we recommend EkkiGreenheartOpepe and Oak for heavier civil/marine uses. For intermediary external use such as decking, where the timber needs to be both strong and durable but not on the same level as civil engineering (bridgespiling, etc) we usually supply CumaruIpe, Jatoba, and Balau. And for the lighter exterior use where the timber is non-structural such as cladding, we deliver CedarLarchThermowood and others.

Which timber is the most durable?

Durability Class 1 timbers are the most durable. This of course depends on the use (hazard) class they’ll be in service for. For direct ground and water contact such as sleepers, fenders, marine piling, etc, Ekki and Greenheart are known to be the most durable timbers available. For decking and cladding where there’s no direct ground contact (use class 3) there’s a much wider range of timbers such Larch, Cedar, Thermo modified Pine or Ash and others.

What’s the best timber for internal cladding?

Internal cladding, where your timber is not in ground and not exposed to the elements can be classed as either use-class 1 or 2 – in which case most timbers will meet this durability criteria. That is not to say they’ll be the best, since internal environments have lower humidity (moisture) levels than outside. So in these cases, it’s best to go for a kiln-dried timber cladding board as these are more stable and delivered already in lower MC (moisture content) than the usual fresh sawn timbers sent to external applications. A word of caution – as timber reacts to variations in moisture, it’s best to avoid cladding any areas inside your bathroom.

How can I make decking less slippery?

The first thing is to ensure your deck boards are kept clean from leaves and other debris which will, over time, cover the surface and make it more slippery. Grooved boards can be used to improve grip if installed and used perpendicular to traffic, so especially useful in narrow passages and footbridges. Lastly, you can add our Grip-Choice strips: these are a mix of epoxy with aggregates that add gripping ridges to your deck area. Gripchoice is an easy way to make decking less slippery and safer, especially over large areas or where there’s high traffic. We can pre-install Grip-Choice strips for your decking before delivery or ship the strips separately to add to your existing deck’s grooves as a retro-fit solution.

What wood machining services do you offer?

We can offer planing, sawing, drilling and profiling of rough-sawn wood to any profile you require: from handrails to large port fenders.

Can you supply pre-drilled timber?

Yes, we will be happy to provide pre-drilled timber which is tailored to your needs for quick installation, thus saving you valuable time on site.

What cladding profiles do you supply?

We provide a wide range of cladding profiles, including tongue and groove, featheredge and shiplap. You can check the standard profiles here – but we can also match or custom make profiles to suit your specific needs.

Does timber change colour?

Yes, timber is well-known for changing colour over time. Some species can darken quickly right after installation, and like most untreated wood will eventually weather to a beautiful silver-grey. Interior timber is less likely to change colour (depending on conditions), and timber can be stained, painted or treated with UV-resistant oils to reduce colour change.

Do I need to treat exterior timber?

Some timbers such as Oak and Ekki, can withstand the strains of exterior use without any treatment. However, to extend the lifespan and maintain the aesthetic of your wood, we do recommend treating your timber with stains and oils. Pre-treated timber, such as ThermoWood and OrganoWood, are low-maintenance options which are more durable, but can have their life service extended by applying a clean and stain maintenance schedule.

Do I need to treat interior timber?

Depends on what area the timber is being used. For floor joists and timber rafters, it is common to see timber treated, or least very well kiln-dried. Other uses such as flooring may benefit from varnishing while internal timber cladding for decorative purposes shouldn’t require any treatment other than if you want to change its colour with different types of stains or oils.

Where are you based?

We’re based in Cambridge, UK, and coordinate multiple sawmills all over the world to manufacture your order. We then organise delivery with a range of hauliers so that your orders gets to your site on time.

What are the usual decking sizes?

Timber decking is usually 21x140mm or similar. For heavier applications where there’s more load and traffic, we deliver 35 or 45mm thick boards (such as Hastings Pier). Narrower boards are also possible: 95-90mm is a standard width – but we can manufacture whatever size you require.

What are the usual cladding sizes?

Typical cladding section sizes are 18×95 and 18x145mm although we can always custom make a section to suit your project’s design requirements. That includes waney edge boards in Oak or Chestnut as well as extra wide 195mm boards.

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