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A timber board may look simple on the surface, but do not be fooled. Beyond the basics of what we can see lies years of evolution and cell growth, with as much biology at play in an Oak desk or Pine dining table as in our own bodies. The anatomy of the trees whence your timber comes is fascinating, and our team at EcoChoice thinks it sheds light on just why this is such an incredible and versatile building material.

Intrigued? Find out more about the anatomy of timber and the trees it comes from in our insightful guide.

Looking at Tree Trunks

If you have ever looked at the stump of an old tree and marvelled at the details on display, you are not alone! The cross-section of a tree trunk reveals amazing features. Moving from the outside to the inner centre, you will see:

  • The bark: The tree’s outer protective layer, shielding it from weather, pests and physical damage.
  • The cambium: A thin, active layer just under the bark where new cells develop, helping the tree grow and expand in diameter.
  • The sapwood: A layer which transports water and nutrients along the axis of the tree, and is often lighter and more susceptible to pests.
  • The heartwood: The strong, inner core providing structural support, which is denser and darker than the sapwood.
  • The core (or pith): The innermost part, a small, soft section from the tree’s earliest growth.

When looking into timber for construction and engineering, you will receive the heartwood or sapwood of the tree depending on your intended application. The inner 5 to 20 growth rings are often called juvenile wood as they were formed in the first growing phase of the tree. This area of timber is not as durable or dense as the more mature timber, so we do not recommend it for construction.

What Are Tree Rings?

Tree rings are a pretty distinctive part of the cross-sectional trunk. They form as the tree grows, with one ring for every year and yes, you really can count the age of a tree using its rings!

These rings form as each growing season is defined by different rates of growth. In the earlier part of the season, the tree grows more quickly and the wood both less dense and lighter in colour. Later in the season, it slows down and becomes darker, creating the distinction needed for rings to form.

Interestingly, ring width can also be used to indicate the strength of timber. When the tree grows quickly it becomes less dense and forms wider rings, telling us that the timber will be of lower quality and less suitable for construction.

Down to a Cellular Level

If you look at timber under a microscope, you will notice that the cells are long and tube-shaped, with each cell being around 2-5mm long and 10-50mm wide. These are known as fibres, and they line up to form the grain of the timber.

The cell walls themselves are made up of several layers which work together to give wood its characteristic strength and hardness. Each layer is made of cellulose fibres embedded in a mix of lignin and hemicellulose, with the fibres oriented differently in each layer. The thickest layer has fibres running parallel to the cell, which is great for handling tension forces. The other layers have fibres at angles between 50–70°, which helps the wood resist buckling under compression.

In softwoods, such as larch and douglas fir the walls of the cells are stuck together by a glue-like substance called the middle lamella, which is rich in lignin. The centre of each cell, known as the lumen, is where nutrients are transported.

Hardwoods such as Oak or Ekki take a different approach, using large-diameter, tube-like cells called vessels to move nutrients. Hardwood fibres usually have smaller lumens and thicker walls than softwood fibres.

The way that the fibres of timber are aligned along the trunk ensures it can tackle the challenges of tree growth with ease, without bending in the wind or buckling under its own weight. This also makes it a great material for construction, bringing strength, durability and load-bearing characteristics to a variety of applications.

Find Your Favourite Timber Species

If you are considering choosing timber for your next project, we can help. At EcoChoice, our timber experts know everything there is to know about wonderful wood, and we will be happy to match your application to the ideal timber species. Get in touch today and let’s talk more about your timber needs.

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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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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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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.

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

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