Guide to Treated Wood

@StylistMagazine has said that 2021 will be all about plants and that there are, “10 eye-catching plants set to take over our homes (and #Instagram feeds) in 2021.”

In addition to filling our homes with plants in 2021, we will also be bringing the outdoors indoors as 2021 home furnishing trends are all about taking inspiration from nature. This means that wooden furniture is at the top of everyone’s wish lists for revamping their homes in 2021.

As such, if you are a DIY enthusiast looking to update your decking, or even a carpenter or joiner, it is important to be well-versed in the different types of treated wood and their uses. This time, we have put together a handy guide on treated wood that you will be able to easily refer to when you are working on your next project.

There are different use classes for treated timber. This is because different environments require different types of wood. Think about the difference between the wood in your kitchen and your garden.

Some treatmented timber might make it only suitable for indoor use in specifically dry areas, such as timber that will be used as tile battens. This means that you cannot buy one type of timber as an all-purpose timber that you can use anywhere. If you used timber that has been treated for Use Class 1 (internal, dry) for a fence post, then you run the risk of the wood rotting and the fence collapsing.

You might think you are saving money but the cost of rebuilding the fence and the loss of animal stock, or other valuables, means it’s a false economy. This is why it is very important to understand the wood that you are working with and the use classes for the next job you are working on.

It works the other way around too. If you were to buy the wrong timber by purchasing UC 5 for a UC 1 job, then you would be spending more money than you need to. This would eat into your budget or profits. These are the reasons why it is so important to understand treated wood and the different use classes.

Use Classes – BS EN335-1

UC 1 – Above ground, covered. Permanently dry. Internal, with no risk of wetting. (eg., Upper floor joists).

UC 2 – Above ground, covered (by a roof), Internal, occasional risk of wetting (eg. Tile battens).

UC 3 coated (3.1) – Coated, above ground, Exposed to frequent wetting (eg. painted cladding above damp course proofing).

UC 3 uncoated (3.2) – Outdoors, uncoated, above ground, exposed to frequent wetting, (eg. Cladding, Fence rails, above damp course proofing).

UC 4 – In contact with the ground or freshwater. Permanently exposed to wetting. Timbers in permanent contact with the ground or fresh water. Direct soil or freshwater contact (eg. Fence posts).

UC 5 – Permanently exposed to wetting by saltwater. All components in permanent contact with seawater.

We hope this is a helpful guide for you to refer to the next time you are working on a project using fabulous treated timber.

Find out more about different wood treatments and learn about our sustainable, eco-friendly approach to timber by exploring our site today.

Image: Brandon Bourdages / Shuttestock.com

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Guide to treated wood

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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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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.

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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.

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

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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

Great service, quality products and very easy to deal with. Thank you.

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  • 6 years ago

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

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