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Timber is a top choice for the engineering and construction industry. From beams to bridges, it brings lightness, versatility and durability to a wide range of building projects. But before working with timber, it is important to understand how the moisture content of your products can impact their end properties. Intrigued? Take a closer look at the role of moisture in timber in this guide.

Does Timber Contain Moisture?

Timber is a hygroscopic material, which means that it absorbs or loses moisture depending on the humidity of its environment. When first felled, wood cut from trees can contain around 60% moisture, which will decrease over time as the timber begins to dry. This water exists as both free water – which remains in the cell cavities – and bound water – which is stored within the cell walls.

Even when kiln-dried, timber will contain a level of moisture. As it dries, though, the free water will start to disappear first until the moisture content is at around 25-35% (also known as the fibre saturation point (FSP)). If the timber dries further than this, the water will begin to leave the cell walls and trigger property changes in your wood products, namely movement, such as checking, bowing, twisting and warping. This is why kilning needs to be done carefully and slowly.

The amount of moisture timber contains is measured using a ratio of the water weight to the dry weight of the timber.

How is the Moisture Content of Timber Measured?

Typically, moisture metres are used to measure the water content of timber. These work by analysing how the moisture influences electrical resistance, and are calibrated for use on different timber species. You can also oven-dry wood to the right moisture content, giving you plenty of control of the water in your timber products.

At EcoChoice, we supply kiln-dried timber for construction projects such as Oak, Douglas Fir, Pine and Spruce, ensuring your species is always dried to the ideal moisture content,

Effects of Moisture Content on Timber

What happens when your timber moisture content falls below or moves higher than the FSP? Let’s take a look at some of the most common effects:

  • Dimensional Stability: Below the FSP, your timber begins to shrink, causing potential warping and cracking. Above the FSP, you are likely to see your timber swell. These movements are what we call ‘dimensional changes’, and we also refer to timber which is less susceptible to shrinkage and swelling as dimensionally stable.
  • Strength and Stiffness: Timber’s mechanical properties also vary with moisture levels. Below the FSP, as the moisture content decreases, strength and stiffness will increase. This is why our sustainable timber used for construction purposes is usually kiln-dried, with the aim of meeting the humidity conditions of your indoor or outdoor environments.
  • Decay Resistance: High moisture levels will make your timber more susceptible to fungal attacks and decay. Timber with a moisture content below 20% is ideal for preventing these issues, and it is one of the main reasons why an understanding of how water affects timber is important.

Other Implications of Moisture Content

The moisture content of your timber can have impacts aside from affecting durability. For example, moisture can affect the thermal and acoustic insulation properties of wood, as well as its weight and density.

Find Kiln-Dried Timber at EcoChoice

Looking for high-quality timber which has been kiln-dried and is ready for construction? We can help. At EcoChoice, we supply high-quality, sustainable timber products sourced from FSC- and PEFC-certified forests, ensuring your project has the materials it needs to last a lifetime. Get in touch with us today to learn more and start your order.

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Impacts of moisture on timber

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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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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

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Average rating on Google Reviews

  • 6 years ago

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

Stone Zone

  • 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

  • 9 years ago

Wonderful guys!

Nicola Edmead

  • 9 years ago

Experts in Timber, Nationwide delivery

Joe Middleton

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