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When constructing a timber deck, one crucial yet often overlooked detail is the spacing between decking boards. But, as anyone who has ever completed a successful DIY project knows, the details matter.

At EcoChoice, we have been helping our clients build decking for decades. Whether you are working on a large deck for a public area or a small, decked area in your garden perfect for your morning cuppa, we can help. Get to grips with decking board spacing in this easy-to-understand guide.

Why Decking Board Spacing Matters

With something as seemingly small as spacing, it is easy to not worry too much about specifics. But when building timber decking, your spacing is absolutely crucial to the success of your construction. Why? Let’s take a look:

  • Timber expands – Material Expansion: Timber naturally expands and contracts when there are changes in moisture and temperature. For example on a humid day, your timber boards might swell. Proper spacing accommodates these movements, preventing warping and buckling.
  • Drainage – Well-measured spacing helps water runoff, improving the drainage of your timber decking to prevent moisture accumulation. In turn this reduces the likelihood of your timber boards rotting, helping your deck last longer.
  • Ventilation – Spacing improves airflow between your boards, which is a must for allowing the timber to dry properly and preventing damp buildup beneath the surface of your decking.

If you do not get the spacing right, you leave your decking at the risk of warping, rotting and falling apart far more quickly than it should.

Recommended Spacing for Timber Decking Boards

We recommend following the advice of the Timber Decking and Cladding Association (TDCA) when it comes to board spacing. They are a super reliable resource, and an organisation which our team at EcoChoice have worked with over the years as a TDCA member.

They advise that your timber decking boards should comply with the following spacing:

  • For boards up to 90mm wide: A gap of 5-6mm is advised.
  • For boards wider than 90mm: A slightly larger gap of 7-8mm is recommended.

These guidelines ensure sufficient space for drainage and ventilation while accounting for timber’s natural expansion and contraction.

How Can You Make Timber Spacing Easier?

To make timber spacing easier and more consistent, use decking spacers or wedges to ensure uniform gaps between boards during installation. A spacer tool helps maintain the recommended gap while preventing boards from shifting as you work. You can also use a decking jig when constructing your decking, which makes drilling precise pilot holes a whole lot easier.

Other Factors to Be Aware Of

How you space your timber decking boards is not the only factor which will create a sturdy deck.

For example, the moisture content of your timber can drastically affect spacing.

Tropical hardwoods, such as Ekki and Opepe, will generally have a higher moisture content than other timber species and will therefore move more than, for example, a kiln-dried softwood such as Thermowood or Larch.

Note that wider boards may require slightly larger gaps to accommodate greater movement, and they will also be needed in places with high humidity or significant rainfall.

Find Sustainable Timber Decking Boards at EcoChoice

At EcoChoice, we help clients across the UK build decking they can rely on. We source and supply sustainable timber, with a wide range of species well-suited to your needs. To learn more or start an order, get in touch with our team today.

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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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