Larch

3.5-4.5 usd/kg
Circularity potential
Very high
Strength
High
Production energy
Ultra low
Stiffness
Medium
Embodied CO2
Low
Density
Low

Larch is a softwood and member of the pine family. It is prized for its strength and durability, and may be used outdoors untreated. The sapwood converts into heartwood relatively quickly, and this is the most durable part of the tree. Its resinous quality protects it from rotting, even in damp conditions.

While they are native to certain parts of the world, most grow happily throughout America, Europe, Russia and Asia. Common types include eastern (Larix laricina) (also known as tamarack and American), western (Larix occidentalis), Siberian (Larix sibirica) (also called Russian), European (Larix decidua) and Japanese (Larix kaempferi).

Slow-grown species, such as Siberian are preferred for structural applications due to their inherently superior mechanical properties. They are converted into structural lumber, as well as engineer timber, such as glulam (glued laminated timber).



Larch is used in construction, boarding, decking, cladding and furniture making. It is a good all round timber suitable for a range of situations. It has a distinctive appearance with tightly packed grain and typically covered in lots of tiny knots. The timber starts of pale pinkish-yellow and gradually darkens with age. Outdoors, it takes on a silvery-grey patina within 10 years or so.

The timber dries quickly, but is prone to surface splits. So, while it makes a good decking material – because it doesn’t require preservatives and the closely packed grain gives it good durability – it can shed splinters and so not so comfortable barefoot.

Interlocking joins between boards, such as tongue and groove are not recommended, due to its relatively high movement compared to other softwoods. Therefore, planks and cladding tend to be butted, feathered, overlapped or spaced out.


Design properties
Cost usd/kg
3.5-4.5
Embodied energy MJ/kg
0.7-0.9
Carbon footprint kgCO2e/kg
0.35-0.4
Density kg/m3
520-650
Tensile modulus GPa
10.6-14.5
Tensile strength MPa
101-134
Flexural strength MPa
94
Modulus of rupture MPa
90
Compressive strength MPa
52.5
Hardness Mohs
1
Poissons ratio
0.27-0.39
Thermal conductivity W/mK
0.12
Temperature min-max °C
-40 to 150
Thermal
insulator
Electrical
insulator