The durability classes of wood
Durability class 1 or 2, you have probably seen it when looking for new wooden planks for your decking or fence. But what does this durability class of wood mean?
The durability class indicates the lifespan of a type of wood.
Wood with durability class 1 is very durable, while wood with durability class 5 is not sustainable. Then there are classes 2 to 4 that are somewhere in between.
But what do these sustainability classes mean for your future garden project? We explain that to you below.
What is the durability class of wood?
The durability class of wood indicates how long a type of wood can last.
To determine the durability class of a type of wood, the heartwood is exposed to bacteria and fungi. For example, it has been investigated which type of wood can withstand this and which cannot.
So it says something about the lifespan of the wood. Wood with a high durability class has a long lifespan and is often a high-quality wood type.
The durability classes of wood give you an idea of whether the wood is suitable for the job you have in mind. This way, you know that with a type of wood with durability class 5, you do not have to make a decking on the water.
What is the durability class for wood there?
The durability classes in wood are on a scale of 1 to 5. Wood types in classes 1 to 3 are most suitable for garden projects. The application you have in mind is also important.
Durability class 1
With wood types in durability class 1, you should think of high-quality woods such as Ipé, Padouk, and Mukulungu.
These woods have a long lifespan and are suitable for many applications, where direct ground contact is often no problem.
The lifespan of these types of wood is, on average, about 25 years or longer (in the case of outdoor use). Especially if you properly assemble and maintain the wood products, the lifespan is often even longer.
Durability class 2
Wood products in durability class 2 are also often hardwoods, such as the popular Bankirai. Wood species such as Kapur and thermally modified Spruce and Pine also fall into this category.
With a lifespan of about 20 years, these types of wood are still very durable but slightly less in quality.
They often work just a little more, are less resistant to moisture, and absorb more dirt than wood types with durability class 1; this is also reflected in the price.
Durability class 3
Many treated softwoods fall into durability class 3. In addition, you will also find hardwoods such as Keruing, which is seen as the lesser version of Bankirai, and thermally modified bamboo.
The price of these wood products is generally lower than wood with higher durability classes, but this is also reflected in quality, function, and lifespan.
Wood species with durability class 3 last about 15 years. Yet you can also make wonderful wooden projects here, such as decking or fences. These types of wood are a real solution for the price-conscious customer.
| Class/Grade | Lifespan | Wood species | Applications |
| Durability class 1 | 25 years or more | Ipé, Mukulungu, Massaranduba, Azobé, Thermally Modified Fraké and Ayous, Accoya, Padauk, Angelim Vermelho. | On/in the water: Decks, fences, facade cladding, furniture wood, boatbuilding, and sheet piling |
| Durability class 2 | 15 – 25 years | Bankirai, Kapur, Thermally modified pine/spruce, Purpleheart, Almendrillo, Chestnut wood, Oakwood, Western Red Cedar, Garapa, Robinia. | For the garden: Decking, fences, cladding, furniture wood, fencing, and pergolas |
| Durability class 3 | 10-15 years | Keruing, Siberian Larch, Thermally modified bamboo, Tigerwood, Impregnated garden wood (spruce/pine), Douglas wood. | Covered in the garden: Decking, fences, canopies, fencing, pergolas, and cladding |
| Durability class 4 | 5 – 10 years | Untreated pine and spruce wood. | Not for outdoor applications, but for the floor of, for example, a log cabin or as construction wood (inside) |
| Durability class 5 | 5 years | Birch, Beechwood, Poplar. | Not for outdoor applications but for indoor floors or sheet material. |
What can increase the durability of wood?
Wood species have a certain durability class, but certain treatments can also increase this. For example, untreated pine and spruce wood are not suitable for outdoor use but impregnated pine or spruce can be used for many outdoor applications.
This is reflected, for example, in decking or fence screens. The advantage of these impregnated woods is that they are very economical and yet have a reasonable lifespan.
The disadvantage is that these types of wood are treated with chemicals, which is not the most environmentally friendly solution.
Another method of treatment is thermal modification. The wood is heated with steam. As a result, types of wood that normally have durability class 5 are suddenly just as durable as high-quality hardwood.
In addition, these types of wood have relatively little effect after the thermal modification process, and they weigh less than untreated wood.
This makes them very suitable as facade cladding. Wood species such as Fraké, Ayous, Spruce, and Pine are often thermally modified.
The advantage of this treatment is that only heat and water are used, which makes it very environmentally friendly.
The disadvantage is that thermally modified wood is quite fragile, which means it can be damaged quickly, for example, with stiletto heels.
In addition, you can, of course, also treat the wood with stain, paint, or oil to extend its life. Check whether these materials are suitable for the type of wood you are going to use.
What to look for in garden wood?
Delving into the durability classes of wood can help you enormously with your choice of garden wood. There are also plenty of wood species to choose from.
That is why it is important to determine what you want to use the wood for.
For example, is it important that the wood can withstand water well? Then choose a type of wood from durability class 1.
Do you think the price/quality ratio of the wood product is decisive? Then durability class 3 may be more for you.
Even with good installation, you can fully utilize the lifespan of your wood products. For example, it is important that your decking, fence, or facade is installed correctly.
This allows the wood to blow dry, which significantly improves the durability of the wood. Getting a broom over your wooden terrace with some regularity also makes a lot of difference in the lifespan.
In addition, avoiding direct ground contact is a good solution for less durable types of wood. For example, make sure that your fence only starts 10 cm above ground level.
