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Timber is well-known for its versatility, strength and unmatched natural beauty. As an exterior construction material for joinery, you cannot make a better choice! Modified timber cladding, for example, can withstand harsh weather conditions. But when exposed to harsh weather and fluctuating temperatures, some timber species can wear a little more visibly than others, which is where thermal modification comes into play.

From decking to cladding, get to grips with how modified timber joinery could be your best bet for exterior builds. Consider how modified timber, especially when used in cladding, can enhance both durability and style.

What is Thermally Modified Timber?

Thermal modification is a chemical-free preservative process used on timber products. During modification, your timber is heated to temperatures typically between 160°C and 230°C in a controlled, oxygen-free environment, where the wood is also subjected to high pressure. This actively alters the timber’s cellular structure, reducing its water absorption and changing its composition to boost durability. Modified timber cladding emerges as a clear solution when aiming for durability and longevity.

While extremely durable timbers, such as Ekki and Greenheart, will not need thermal modification, it can be great if you want to use a less dense timber, for example Pine, Ash or Spruce, especially as non-structural cladding. Modified cladding can really elevate the performance of these species.

Why Use Thermally Modified Wood for Exterior Joinery?

A huge perk of using thermally modified timber (or ThermoWood) for exterior joinery is its enhanced dimensional stability. As the treatment significantly reduces the timber’s ability to absorb and release moisture, it makes it less likely that your timber cladding will experience swelling and warping. In joinery, where tight tolerances and snug fits are crucial, this level of dimensional stability is a must to stop gaps and splits from appearing in your structures.

Thermal modification also gently increases its resistance to decay. By burning the sugars that attract fungi and rot, thermo woods end up being likely to last equal or longer than the original wood. Timber modified for cladding ensures prolonged effectiveness against decay.

Your decking and cladding will also be less prone to surface checking and splitting, even under extreme weather conditions. This is handy as the UK’s weather becomes slightly more erratic. When it comes to incorporating modified timber cladding, its ability to withstand such conditions is invaluable.

A Sustainable Timber Treatment

At EcoChoice, we are all about keeping the use of timber in construction as sustainable as possible. It is no surprise, then, that we love using thermal modification as a treatment for external joinery. It is a much greener option than some chemical-reliant preservatives, which are not so great for our natural landscape.

You can also use thermal modification to enhance fast-growing timber species, such as Birch, reducing pressure on slower-growing hardwoods. These species replenish far more quickly, supporting responsible and sustainable forest management. Now that is music to our ears. Enhanced timber through modification supports sustainability and growth.

What to Know Before Using Thermally Modified Wood

While thermally modified timber offers a heap of performance advantages, it can be more brittle than untreated timber. This does not have to be a huge issue, as long as you can make slight adjustments to your joinery techniques. For example, it can be smart to avoid direct screwing, which can cause your timber to splinter and opt instead for pre-drilling. When working with modified timber cladding, planning these adjustments can ensure it achieves its maximum potential.

Find Thermally Modified Timber at EcoChoice

Won over by the many benefits of thermally modified timber for your external joinery? Jump on the EcoChoice bandwagon! We are big fans of this tough, durable timber, and supply it to eco-friendly exterior construction projects around the UK, including both domestic and commercial sites.

To start your order of thermally modified timber, reach out to us today.

Modified timber joinery

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Unsure which timer is best for your project?

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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What our customers say about us

Good quality, great service, fast delivery!

5

Marinella Li

Always helpful! One of our valued TDCA DeckMark and CladMark accredited supplier members which means their quality procedures are routinely audited and stand up to scrutiny giving you extra peace of mind.

5

Janet Sycamore

Having needed the supply of cladding, decking boards and other specified timbers through out the year Eco choice have been very helpful in sourcing the specified timbers and quantities required at a very competitive price.

5

Tim Saunders

Great quality, service and price. A pleasure to deal with. I would highly recommend Eco Choice.

5

Emma Hurrell

Fantastic company- Mike and the team are the best in the business- worked with them for many years.

5

Prem Raja

Always reliable and quality products, easy to deal with company.

5

Stone Zone

4.9

Average rating on Google Reviews

  • 3 years ago

Always helpful! One of our valued TDCA DeckMark and CladMark accredited supplier members which means their quality procedures are routinely audited and stand up to scrutiny giving you extra peace of mind.

Janet Sycamore

  • 9 years ago

Experts in Timber, Nationwide delivery

Joe Middleton

  • 9 years ago

Excellent service and outstanding product

Cindy Dicks

  • 6 years ago

Having needed the supply of cladding, decking boards and other specified timbers through out the year Eco choice have been very helpful in sourcing the specified timbers and quantities required at a very competitive price.

Tim Saunders

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