Isn’t It Good; Exterior Wood? #
With summer now hitting us in its fullest bloom, it’s the perfect time to organize some high-quality wood, get some tools, and start working on those long-term garden or outdoor projects you’ve been putting off.
When it comes to these kinds of builds, there’s one factor you should always sit down and address before getting stuck into the meat of the endeavour: what wood should you actually use? There is a wide variety of potential choices out there for your outdoor projects, each of them with their own pros, cons, and situational qualities.
So, let’s go over some of the options that can help your deck, garden furniture, or other project stand the test of time.
Any Wood May Do #
Before we get into specific woods, one important thing to note is that any wood can potentially work well outside for small-scale projects, so long as you keep it dry and well-maintained.
The primary issues that can arise for wood stored outside include damp, decay, and staining. Take the time to find the right spot in your garden, or on your property. Make sure it’s not too exposed to direct, harsh sunlight. Try and keep it on dry grass, stone, or other areas not prone to flooding or excessive moisture. If the wood has to come into contact with the ground, make sure to use rot-resistant wood.
Sometimes, you already have the perfect piece of wood in mind for your project – one that maybe has sentimental value, unique meaning to you, or even just a large section you have left over from a different project. As long as you take care of it, you don’t need to be drawn into the idea that you absolutely have to buy a new piece just for this project. If this sounds like it describes you, go right ahead and skip to the Treatment section of this article. But if you are in the market for a new piece, there are a number of potential options for us to cover:
Ash is a beautiful and historically significant wood, but it’s very unsuited for outside use. Its natural properties, most notably its flexibility and its capacity for shock absorption, also make it more likely to rot. Ash trees in the wild often have problems with insects, and the same is true for ash when used in furniture, decking, cladding, or other exterior options. Ash will work fantastically for the handles of the tools you use for the outside project, but we don’t recommend you use it for the outside project.
Beech, much like ash, is a beautiful, strong, and long-lasting wood that really doesn’t take well to being used outdoors. Once it’s been cut, it reacts very badly to changes in temperature and humidity. It develops black mildew and other fungal infections much more readily than other types of tree, and this fungal risk is especially high in damp or humid environments.
The main issues with using birch as an outside wood lie in two separate factors – its water-resistance (or the lack of it), and its durability. While the bark of birch wood is historically good at resisting water (hence its use by Native Americans in canoe-making), the wood you’ll buy from the shops will most likely be shaved, and raw birch doesn’t react well to the rain, damp, or humidity. Birch is also often prone to decay and fungal infection.
Douglas Fir #
Douglas fir is widely regarded as being perfect for outdoor projects, owing to its natural strength, resilience to fungal infections, high density, and sap content. You can easily find it at any good sawmill or specialty shop, and you can work with it yourself very easily, with the wood taking easily to hand or machine tooling. For these reasons, it’s common to find Douglas fir being used outside in all manner of projects, from decking or cladding to garden furniture.
If you’re looking to treat your wood, there are many stains and preparations tailored to Douglas fir, and it takes to them and to weather-treatment incredibly well – however, even if you want to use untreated timber, it can still endure any moderate climate for a long while without any significant issues cropping up.
Douglas fir is also characterised as a very fast drier, which is ideal if you live in a naturally wet environment. Its broad availability and widespread use in the field also means you can very easily find advice about it on specialist forums, and plans that reference it directly. All these qualities and more have made Douglas fir a favourite for us at Logie Timber, and we’re very experienced at working with it.
Elm, on the surface , might seem to be a great wood to use outside. It’s naturally very strong; has a terrific degree of water resistance; and it sands, stains, and paints well. However, although it’s a fantastic wood for furniture, elm often struggles to hold up outside.
Elm often warps during the seasoning process, has a very poor ability to defend itself against insects or fungal infection, and its reputation for water-resistance largely relies on its ability to halt decay entirely if it’s fully submerged in water. If exposed to highly seasonal weather, such as rapid shifts between high and low humidity, this vulnerability to decay can become even worse! Even using a high-quality sealant or stain can’t prevent the problems, as humid moisture can work its way in under the coating. Unfortunately, elm is a terrible choice for outdoor construction.
Larch is a fantastic option for outdoor construction. Especially in Scotland, larch has a historic reputation as being water-resistant; often being used for tasks like fences, gateposts, foundational logs, the hulls of fishing boats, and other jobs that require a near-constant exposure to water. This gives it a naturally high level of decay resistance, and its innate durability means that you can handily use it for extensive outside operations, like decking and cladding, without even needing to worry about regular maintenance.
While larch takes stains made for it very well, it also benefits from a high level of natural durability that can kill off any threats. Larch is another favourite for us at Logie Timber and comes highly recommended for use in exterior construction.
Poplar struggles to hold up in exterior conditions, largely due to its inability to form a consistent, strong heartwood. This makes it less suited for use outside, due to its increased risk of decay. If finished well and kept in an area with minimal risk of rain exposure or high humidity, poplar can perform acceptably, but it’ll never be as suitable a wood as larch, cedar, or Douglas fir.
Poplar’s pliable surface dents and scratches more easily than other woods, even when finished, making it less suitable for use as a furniture wood. Even sealing or treating the wood (a more difficult proposition with poplar than with most) doesn’t help mitigate the risk of decay, as moisture can always seep its way under the coating, and you can’t rely on poplar’s natural durability in those circumstances.
Western Red Cedar #
Cedar generally is an ideal wood to use outside, owing to its soft colour, easiness to work with, and its notable resistance to insect attacks and fungal infections. All the cedar varieties from North America are renowned for their durability against insects, and our Scottish-grown varieties of this American classic have inherited that same admirable quality.
Much of the protective elements of cedar that help it resist infection lie in its natural resins and saps, which mean that it also works excellently if you want to leave your wood project untreated. You should be aware that cedar has comparatively poor screw-holding capabilities compared to other woods like it, but there exist any number of screw alternatives or joint-based options if that truly is a worry for you.
It’s also softer and more brittle than some of the hard-wearing options like larch or Douglas fir, but that in turn makes it ideal for use in projects that you want to be spending time sitting on, like exterior furniture or cladding. We at Logie Timber are proud to recommend our Western Red Cedar for exterior use.
Scots Pine #
Pine is a commonly used wood for small-scale projects and beginners in woodworking, and for good reason. It’s often an affordable option, easy to cut, easily sourced almost anywhere, and takes well to painting. However, the difficulty with using pine outside is that you absolutely must treat it in order to avoid decay or insect/fungal infection, because the wood is naturally not resistant to either issue – and, finishing it with regular wood finish or stain poses another problem.
The wood’s uneven pores mean that it soaks deeper into the earlywood than the latewood, leaving it patchy and unevenly protected. This poses a problem if you want to leave your wood untreated. Untreated pine is also at greater risk of warping or cupping. However, as long as you use a good-quality exterior sealer or similar finish, pine should hold just fine. It’ll be particularly suitable for projects like garden furniture.
As with several other options here, spruce just isn’t a good choice for outside use owing to its lack of rot and weather-resistance, as well as its vulnerability to insect attacks. Its moderate durability rating means that there are a wide number of other options available that achieve the same benefits as spruce (chiefly, its strength-to-weight ratio and workability) with better resistance to the elements, such as larch and Douglas fir.
Sycamore wood, like with ash and birch, is a fantastic interior wood for furnishings and flooring that really just isn’t recommended for exterior work. The main problem lies in its lack of exterior durability. It has a very high moisture content; so high, in fact, that the heartwood of mature sycamore trees can often be found rotted, and that’s even in the wild. It stands a high chance of decaying rapidly, and treating will only help so much.
Oak is a commonly used wood for exterior projects. It’s internally strong, widely known for its durability, and its beautiful natural colour makes it ideal for statement pieces of garden furniture, or quality decking that can weather well and always stand out.
Oak is also an ideal wood to use in water-logged environments, or areas with heavy rain, owing to its high level of water resistance – such a high level, in fact, that they even used to make ships from it, and it’s a preferred wood for wine and whisky makers internationally. This makes it even more ideal for an environment where you’d prefer untreated wood, such as for decking, garden furniture, or anything that serves a domestic function.
Leaving oak untreated even has an aesthetic appeal, as oak exposed to UV radiation can develop a sun-drenched, silver hue. (If you want to avoid this change, UV protection oils are available.) Its high tannin content also makes it very resistant to fungal infection and insect attacks.
Oak, whether treated or untreated, has a tremendously long lifespan – easily two to three times that of many other comparable hardwoods. This is matched by it being more expensive than other woods on the market – but, like with many things, we at Logie Timber find it’s often the case that you get what you pay for. Our oak rates are highly competitive with others on the market, and we’re more than happy to recommend our oak for exterior use.
Many of the woods listed above, even if we wouldn’t advise them for exterior use, can still hold up outside with only minor issues – as long as you apply the proper treatment. However, even if you plan to apply a coating to your wood, it can still be advantageous to pick one that’s known for its natural durability and resistance to rot, fungal infection, or insects. This is because no treatment, no matter how well-applied, can fully protect against all of these issues. The more natural protection your wood has, the better it will hold up when worse comes to worse.
There’s also the time, effort, and expense to consider. Leaving your wood untreated isn’t always the best idea (especially if you live somewhere especially wet or humid), but bear in mind that a particularly unsuited wood will have to be re-coated and re-treated a lot more often than a more durable one.
That being said, a good treatment can help lock in the wood’s natural resins, protect it from UV radiation, provide further elemental protection, and generally grant you further peace of mind about the ongoing health of your wood.
For treating our woods, we always recommend TreaTex: quality finishes made from naturally sourced oils and waxes that will help your wood get the best lifespan and finish quality, with the least environmental impact. Even if you have environmentally resistant wood and a good finish, though, you shouldn’t get cocky! If your project can be easily covered (for instance, if it’s furniture), make sure to cover it with a sheet during periods of heavy snow, ice, or consistently heavy rainfall to help mitigate the chance of rot. If it can’t be easily covered in those conditions (e.g. decking), make sure to wipe it down regularly instead.
There are a lot of factors to consider when you’re choosing what wood to use outside. At the end of the day, there are decisions you should make yourself that just come down to personal preference, such as the look, the colour, or even just an affinity you might have for the tree the wood came from.
However, when you’re considering a significant investment you want to be a centrepiece in your garden; a valued space for social gatherings; or even just an unassuming bench you want to last for decades or more, it’s very important to consider the practical matters behind the wood you choose.
You should always make sure you do your own research before making a purchase, but hopefully this guide has helped you on the way to making that crucial choice. If you have any further questions about what wood would be most suitable for your outdoor project.