The decorative qualities of larch can be used in interior fitout, and as an exterior feature cladding.
Larch is a deciduous conifer, and is grown in several sites in New Zealand, mainly within the South island. Larch performs best on lower hill slopes and valleys sheltered from wind.
The heartwood of European larch is an attractive yellowish brown, the sapwood a paler brown. It has prominent growth rings, although not quite as prominent as Douglas-fir.
The combination of wood colour, interesting ring patterns, and small, tight knots randomly distributed make this a particularly attractive wood for uses such as panelling.
Botanical name: Larix decidua
Other common names: European Larch
Strength: Particularly strong.
Durability: Although the timber is nearly all heartwood, and European-grown larch displays moderate durability, larch grown in New Zealand is non-durable in ground contact and is difficult to treat with preservatives.
Finishes: Larch glues satisfactorily and takes all kinds of paints and stains.
Working properties: Pre-boring is usually necessary before nailing; and the wood has a slightly corrosive action on iron nails.
Appearance: The heartwood of European larch is an attractive yellowish brown, the sapwood a paler brown.
Larch is a medium density softwood, with shrinkage (from green to 12% moisture content) of 4.9% in the tangential direction, and 2.0% radial. Due to a small juvenile core, the timber is fairly dimensionally stable, but can sometimes be prone to twist, particulary where larger sizes are used.
Although the timber is nearly all heartwood, and European-grown larch displays moderate durability, larch grown in New Zealand is non-durable in ground contact and is difficult to treat with preservatives.
The timber heartwood is not susceptible to borer attack, and the softwood will not be attacked by household borer if kept below 15% moisture content, which is very achievable in most NZ climates. Larch is not an easy timber to machine, the knots having a tendency to “pick out”.
Pre-boring is usually necessary before nailing; and the wood has a slightly corrosive action on iron nails. Larch glues satisfactorily and takes all kinds of paints and stains.
Larch is a particularly strong timber, with a modulus of rupture of 97 MPa, and has average stiffness properties of 9.7GPa. Larch and redwood are included in MAF statistics which show a total planted area of 26600 ha for softwoods other than radiata, Douglas fir and cypresses. The median age is approximately 15 years.
Strength values refer to 20 x 20mm clearwood specimens.
Please note these comparative measures of strength are “laboratory” values using standardised short lengths of clear timber. These will not be the same strength properties as structural lengths of timber.
For the properties of structural length timber please see the tables under the structural design section.
Density at 12% M.C. 512kg/m3 Modulus of ellasticity 9.7 GPa Bending strength 63 MPa Compression strength 50 MPa Hardness 3.1 kN Shrinkage green to OD, tang 5.0% Shrinkage green to OD, rad 2.0%
- Case Study
In this example, larch has been used for exterior cladding.