Types of Wood Cladding Explained
Published: 18/01/21 By: Mike Bekin
Before we get to wood cladding, for those who don’t work in the construction industry, let’s look at what cladding is first.
Of course, at the moment in the UK, the word ‘cladding’ in the construction industry is a real watchword. After the Grenfell Tower disaster in North Kensington in June 2017 fire safety in tall buildings has been looked at closely, “The 24-storey block was clad in aluminium composite material or ACM which is now known to be dangerously combustible.”
Using wood as a cladding material offers many advantages and woods such as OrganoWood not only last a long time, weather to a pleasant grey tone, but are also resistant to fire.
Now that we have identified what cladding is let’s move on to the different types of wood cladding. Some types of timber are more durable than others.
There are five different durability classes. The durability rating is based on the heartwood only. Heartwood is the central part of trees. It is mechanically strong, resistant to decay, and less easily penetrated by wood-preservative chemicals than other types of wood.
Natural Durability Class BS EN 350: 2016 |
Desired services life/years Occasionally wet (with coating) |
Desired service life/years Frequently wet |
1 – Very Durable | >60 | 60 |
2 – Durable | 60 | 30 |
3 – Moderately Durable | 30 | 15 |
4 – Slightly Durable | 15 | <15 |
5 – Not Durable | <15 | <15 |
The rows highlighted in yellow will all need to be appropriately treated to extend their service life.
Principal softwood species used in the UK for cladding
Common name |
Natural Durability Class (BSEN350: 2016) |
Sapwood Treatability | Movement | Density kg/m³ | Availability |
Douglas Fir | |||||
Home grown | 3 – 4 | Resistant | Small | 470 – 520 | Specialist supplier |
North American | 3 | Resistant | Small | 510 – 550 | |
Larch | |||||
European | 3 – 4 | Resistant | Small | 470 – 650 | Specialist supplier |
Hybrid (aka Dunkeld) | 3 – 4 | n/a | n/a | n/a | Specialist supplier |
Japanese | 3 – 4 | Resistant | Small | 520 | Specialist supplier |
Siberian | 3 – 4 | Resistant | Small or medium | 680 – 700 | Good |
Pine | |||||
Scots Pine / European redwood | 3 – 4 | Permeable | Medium | 500 – 540 | Good |
Lodgepole Pine | 3 – 4 | Permeable | Small | 430 – 470 | Good |
Radiata Pine | 4 – 5 | Permeable | Medium | 420 – 500 | Specialist supplier |
Southern Yellow Pine | 4 | Permeable | Medium | 650 – 670 | Specialist supplier |
Spruce | |||||
Sitka Spruce / European Whitewood | 4 – 5 | Resistant | Small or medium | 400 – 450 | Good |
Norway Spruce | 4 | Resistant | Medium | 440 – 470 | Good |
Western Red Cedar | |||||
Home grown | 3 | Resistant | Small | 330 – 390 | Specialist supplier |
Canadian | 2 | Resistant | Small | 330 – 390 | Specialist supplier |
It is also possible to enhance the performance (durability and stability) of most of the types of timber listed above, through either chemical, biological, or heat processes.
The primary objective in modifying wood is to make them more durable (less prone to rot). This makes modified woods last longer than unmodified woods. The most commonly modified timbers for cladding in the UK are depicted below. Thermowood® mnetioned below is the registered process controlled by the Finnish Thermowood Association – we sell this and also other types of thermo modified timbers
Modification process / brand | Base species | Assigned Natural Durability Class | Dimensional stability / movement | Strength | Coating performance |
Thermally modified timber | |||||
Thermowood S² (190°C) | Pine or Spruce | 3 | Improved + | Unchanged | Improved |
Thermowood S² (185°C) | Birch or Aspen | 3 | Improved ++ | Reduced | Improved |
Thermowood D (212°C) | Pine or Spruce | 2 | Improved + | TBC | Improved |
Thermowood D (200°C) | Birch or Aspen | 2 | Improved ++ | Reduced | Improved |
Thermodified Frake | Black Afara | Improved ++ | TBC | Improved | |
OrganoWood | Pine or Spruce | 2 | Improved ++ | Unchanged | TBC |
TMT Ash / ThermoAsh | American Ash | 1 | TBC | Unchanged | Improved |
Chemically modified timber | |||||
Accoya (510kg/m3) | Radiata Pine | 1 | Improved ++ | Unchanged | Improved |
There are also hardwood species such as Oak, Iroko and Cumaru that are suitable for cladding, although due to their usually higher density and strength, special attention is needed when fixing them.
Cladding also makes a building more aesthetically appealing as we stated earlier. The tradition of using cladding to enhance the appearance of a building goes back a long way and is still universally appealing.
In Ancient Japan the charring tradition of Shou-Sugi-Ban was used for centuries to make their buildings resistant to fire, rot, insects and UV effects from the sun. The practice started in the 18th century. Buildings clad in Shou-Sugi-Ban treated cladding can be protected for up to 120 years. We have now added charred Larch to our range of cladding – with a wide choice of charring levels.
And because timber is a natural product, using wood cladding means that you are protecting your home as well as the planet. In this year of #WoodCO2tsLess, doing anything you can to help reduce the world’s CO2 emissions is an incredible step in the battle to fight climate change.
EcoChoice are dedicated to fighting global warming and to encouraging people to switch to using independently certified sustainable wood for their construction and design work.
Speak to us on 0345 638 1340 to find out how we can provide you with the exact sustainably sourced materials you need for your next project.
Let’s work together to tackle climate change #WoodCO2tsLess.
Tags: Cladding, ThermoWood
Categories: Insights