Class 1–2
Robinia
The most durable wood species that grows in Europe — and with a rotation of 20 to 30 years, fast-growing too.
- Strong in
- fencing, posts, outdoor furniture, decking
- Strength
- highly resistant to rot, without treatment
Durable wood species for outdoor use in Western Europe
The Wood Guide · Choosing and comparing
Buying guideDurable wood for outdoor use
In Belgium, the Netherlands, France and Germany, demand is growing for wood that lasts outdoors without tropical forest being involved. That is possible — with the right species and the right design.
- Five species from our own region
- Four treatment methods compared
- Design counts for more than the species
Three considerations
In pictures · Durable wood for outdoor use1 / 5
Chapter 1 · The species
Durable wood for outdoor use
In Belgium, the Netherlands, France and Germany, demand is growing for wood that lasts outdoors without tropical forest being involved. That is possible — with the right species and the right design.
Click a chapter or use the arrows.
What "durable" is about
The word covers two things you should not confuse: how long the wood lasts, and how responsibly it was produced. Both count.
Natural durability
The resistance to moisture, fungi and insects, expressed in classes 1 to 5 of the European standard EN 350. Class 1 lasts more than 25 years in ground contact, class 5 less than five.
Local origin
Wood from European forests travels a fraction of the distance of tropical hardwood — and the supply chain is more transparent. Simply ask your supplier where the wood comes from; a supplier who knows is already telling you a lot.
Lifespan above all
The most sustainable wood is the wood that stays in place the longest. A structure that has to be replaced after eight years costs more forest than one that lasts thirty years.
From our own region
Five species that last here
All grown in Western Europe, all without a tropical supply chain.
Class 2
European oak
The heartwood is very durable and available everywhere in our region. Strong, heavy and full of character.
- Strong in
- garden furniture, decking, outdoor structures
- Watch out
- tannin turns black on contact with iron — use stainless fittings
Class 2
Sweet chestnut
As durable as oak but lighter, and so easier to work. The traditional choice for fencing.
- Strong in
- fencing, outdoor furniture, decking
- Strength
- locally available, naturally rot-resistant
Class 3
Douglas fir
The strongest softwood, with an excellent strength-to-weight ratio and widely grown in European forests.
- Strong in
- cladding, decking, garden structures
- Strength
- affordable, greys to an even silver grey
Class 3
Larch
The most resinous of the European softwoods; that resin gives extra protection from within.
- Strong in
- cladding, decking, garden sheds
- Watch out
- greys less evenly than Douglas fir
One class more
Four ways to make wood more durable
Species that are naturally less resistant can be upgraded. Each method has its own price — in money, in properties or in environmental impact.
Thermal modification
The wood is heated in a low-oxygen environment, without chemicals. The cell structure changes, which raises the resistance to moisture and fungi and deepens the colour.
To be fair: the heating also makes the wood more brittle. It is less suitable for load-bearing structural parts.
Acetylation
Treatment with acetic anhydride that alters the cell structure. The result is exceptionally dimensionally stable and durable, without toxic substances — Accoya is the best-known example.
To be fair: the price comes close to tropical hardwood, so work it out over the lifespan.
Pressure treatment
Protective substances are forced deep into the wood structure under pressure. That gives long-lasting protection against rot, fungi and insects — it is what makes our spruce picnic tables possible.
To be fair: it is a chemical treatment. Choose environmentally friendly products and take into account the rules on processing and disposal.
Natural surface treatment
Linseed oil, beeswax or modern wood oils protect against UV and moisture without masking the natural look. See the wood oils by colour.
To be fair: this only sits on the surface. It extends the lifespan, but does not lift a species into a higher class.
The underestimated part
Design matters more than the wood species
Class 1 wood that is badly placed lasts less long than class 3 wood that is well placed. These four principles count for more than the choice itself.
- Avoid direct ground contactUse concrete footings or steel post supports. Wood standing in the soil absorbs water and rots from below — whatever its class.
- Make sure water runs offDesign sloping surfaces and avoid spots where water stands. Standing water is the main cause of wood rot.
- Let it dryEnough air circulation around and under the wood does more for its lifespan than any coating.
- Protect against driving rainA canopy or an overhanging roof edge keeps most of the rainwater away. The end grain deserves attention too: that is where wood absorbs the most.
After that
Maintenance and lifespan
With the right maintenance, the better species reach twenty to thirty years or more.
Clean every year
Remove dirt, algae and moss — they hold moisture against the wood.
Treat periodically
Touch up with oil or stain every one to three years, depending on exposure. The water test tells you when.
Inspect in good time
Check for signs of rot or damage and repair straight away — that way small stays small.
Through the winter
Cover furniture with a breathable cover or bring it indoors. Never wrap it airtight: condensation does more harm than rain.
Why wood is a good choice either way
Wood stores carbon throughout its whole life, grows back in responsibly managed forests, takes less energy to produce than concrete or steel, and at the end can be reused or composted. The longer a piece stays in use, the better that balance works out — one more reason to choose a species that lasts.
The practical approach for each treatment is in our maintenance guide for softwood — the principles also apply to the species on this page.
Quick answer
Frequently asked questions
Which European wood species lasts longest outdoors?
Robinia — often called "acacia" in everyday speech, but not the plantation acacia used for garden furniture — comes top with durability class 1 to 2, followed by oak heartwood and sweet chestnut in class 2. Douglas fir and larch reach class 3.
Is thermally modified wood as durable as tropical hardwood?
Not quite, but it comes close. Thermal modification raises the resistance to moisture and fungi without chemicals; it does make the wood more brittle, so it is less suitable for load-bearing parts.
What exactly is acetylation?
A treatment with acetic anhydride that alters the cell structure. The result is an exceptionally dimensionally stable and durable product without toxic substances. Accoya is the best-known example.
How long does durable wood last outdoors?
With the right design and maintenance, the better species reach twenty to thirty years or more. Bear in mind: design counts for more than the species. Wood that can dry and does not stand in water beats any coating.
Is pressure-treated softwood a sustainable choice?
It is a defensible one: fast-growing European wood that reaches class 3 to 4 through impregnation and so lasts ten to fifteen years outdoors. We use it to build our picnic tables . More about that in the spruce guide.
More in The Wood Guide
Choose with knowledge
Every species in this guide is explained separately in our register — including the honest drawback.
Have a question about your project? Just ask — we're happy to help.
Photos via Wikimedia Commons: Castanea sativa, Flexham Park (England) — Charlesdrakew, CC BY-SA 4.0 · Robinia pseudoacacia — Lumbar (Wikimedia Commons), Public domain