Douglas Fir vs. Larch
If you’re looking for a strong, natural wood that can stand up to punishing outdoor conditions without treatment, you’ve got a lot of good choices. However, if you ask around – especially for the best timbers grown in Scotland – you’ll find that two get mentioned fairly frequently: Douglas fir and larch. Let’s run down some of the qualities and drawbacks of these two species, especially when compared against each other.
Larch is Great For...
- Cladding (stands up great to all kinds of weather)
- Decking (strong and cost-effective)
- Boat frames (naturally very water-resistant)
- Flooring (naturally resinous, resilient to stains and infection).
Douglas Fir is Great For...
- Cladding (very cost-effective, easy to machine yourself)
- Frames (housing and interior construction)
- Posts and beams, such as in fences or garden gates (stains well, holds up to bad weather when treated)
- Fine joinery and furniture (very durable, accepts nails well)
- Flooring (versatile wood that works well in a number of configurations).
Natural Properties & Qualities of Douglas Fir and Larch
Unlike other building materials, different types of wood can have wildly different characteristics. A wood that really catches your eye, like Scottish oak, can be entirely unsuitable for the project you have in mind (in oak’s case, because it contains various tannins that can corrode iron). When making any purchase, it’s good to be informed, and you’ll often find that things you appreciate in one wood (colour, texture, resiliency) can be found in others that are more suitable or cost-effective.
Douglas Fir
Douglas fir, a large evergreen species, produces a light reddish-brown heartwood, although the sapwood on top is actually pale in colour with clearly marked growth rings and a number of hard, loose knots that run the risk of falling out on thinner boards. It usually has a straight grain, and dries quickly, without much checking (J-B hyperlink) or distortion. The wood itself is very resinous, but more so in native American Douglas firs than in British examples. These British trees can also produce a wavier grain than American timber. When it’s dried, Douglas fir is a notably strong wood, and, after it’s been dried, is very stable in use.
Larch
Larch, a deciduous (J-B hyperlink) conifer (J-B hyperlink), produces a red heartwood that ranges from pale to brick-red, while the sapwood on top is a yellowish white.
It produces a timber that dries rapidly but tends to distort, split, or check. It also has a number of small, dead knots, that may fall out on thinner boards. Timber from aged larch is one of the heaviest British softwoods, but timber from younger trees weighs a lot less. The wood is one of the strongest softwoods, with a close similarity to Scots pine – however, it’s often a lot more difficult to work with.
Preparation & Treatment of Douglas Fir and Larch
Douglas Fir
If you need to work on the wood yourself, you’ll find Douglas fir relatively easy to work with using either machine or hand tools. However, be careful when using hand tools, as the knots can have a greater dulling effect on them than other woods. Those hard, loose knots are especially dangerous to cutting edges, and you want to make sure any cutting, planing or moulding tools are very sharp to achieve the best finish.
Douglas fir should have no problems with nails or screws, so long as you take care to space them apart. When it comes to staining or varnishing, the wood can stain very effectively and works well with a variety of finishing products (such as TreaTex’s Douglas Fir Protection), as long as you take care to prevent grain-raising (J-B hyperlink) and make sure that the timber you’re buying has been aired. Also, don’t apply the oil in cold, damp weather.
All in all, given sufficient preparation (and sharp tools), Douglas fir is comparably easy to modify and work on.
Larch
Despite its natural qualities (namely strength and durability), you might find larch a little trickier to work with than Douglas fir. Even while on the saw in the sawmill, it often tends to spring off, leading to wastage. Once dried, the wood takes to sawing and modification relatively easily, but its numerous small, dead knots can have a blunting edge on the cutting edges of tools.
Because it’s so resinous, it’s best left uncoated, but can also take exterior grade oils, paints, stains, and varnishes well (such as TreaTex’s Larch Oil). Make sure you fit larch cladding when it’s freshly cut – as it dries, it can become more prone to splitting. (And if you are going to nail larch, ring shank nails work well, providing you observe minimum spacing.) If you’re using larch for an outdoor construction, such as a deck, you might want to apply some kind of finishing treatment to achieve the best durability possible. Be careful when it’s lying horizontally, as that might make it make it more vulnerable to rotting as a result of sitting water.
Uses of Larch and Douglas Fir
Douglas Fir
Douglas fir is primarily used as a construction wood and chiefly indoors, due to factors like its high density and low sap content. It also often appears in joinery, due to its stability as a platform and fine appearance. Douglas fir is a uniquely versatile wood and can be used in all manner of projects of different scales, from decking or cladding to furniture. If it’s properly treated, Douglas fir can also perform well in any given climate or environmental conditions.
Larch
Larch is mainly used for exterior work, and generally prioritised for projects that are either in contact with the ground or water for prolonged periods. As a great example of this, larch has been very commonly used in the construction of fishing boats in Scotland throughout history. Larch works best in large-scale constructions, such as timber-framed housing, fences, and gates, where the scale of the project allows the wood’s inherent strength to stand up to drilling and nailing better than in smaller projects. As a wood, it works very well in cold, damp environments, but can struggle even in mild temperatures (potentially warping or distorting in the heat) without some form of treatment or preservation.
Cost of Douglas Fir and Larch Timber
Unlike in all the other elements of this comparison, where larch’s weaknesses (difficulty in nailing, sap run-off, unreliability in the mill, etc.) are often compensated for by its greater strength and durability, in terms of pure cost-effectiveness there’s not really any doubt. Douglas fir is, as a rule, generally cheaper than larch. The difference, however, is quite small – so if you had your heart set on larch and you’re working on a small project, it won’t cost you that much more. For instance, if you were making some relatively standard decking (140x27mm with a 10mm gap), buying larch would cost you £31.83 (plus VAT) per square metre*, whereas Douglas fir would be £29.57 per square metre.
Summary
Both larch and Douglas fir are fine, durable construction softwoods, suitable for a number of different construction projects. However, when working with either, you need to be wary of their weaknesses.
Larch will be perfect for cladding, decking or boatbuilding here in our often-temperamental Scottish weather, with a near unparalleled strength for its cost and weight. However, its temperamental nature means you should make sure you use screw fixings or spaced shank nails to avoid it cupping or twisting out of shape. Also, be aware of the sap if you’re planning to use fresh larch inside or in an area people will be brushing past.
Douglas fir isn’t as strong as larch, but it’s a lot easier to work with, lighter in weight, more stable and more versatile. Its cost-effectiveness and ease to paint or oil make it very effective for indoor construction of any scale. Just make sure you’ve got sharp tools!
*Any prices quoted were accurate at the time of writing – please check our website for up-to-date information.