Western Larch
Western larch (Larix occidentalis) grows in valleys and on the lower slopes of mountains in the southern Interior of British Columbia. As it is intolerant to shade it does well in open stands. This large tree can grow to 80 metres tall and 1.5 metres in diameter. Western larch usually grows in mixed stands with Douglas-fir, western hemlock and lodgepole pine. Larch makes up only 0.7% of British Columbia's total growing stock, yet it is a very important species for producing heavy timber.
Common Uses
Western larch produces heavy, hard and strong wood. It is used mainly in building construction for rough dimension, small timbers, planks and boards, and for railroad crossties and mine timbers. It is used also for pilings, poles and posts. As it is a visually appealing species, some high-grade material is manufactured into interior finish, flooring, sashes and doors.
The properties of western larch are similar (and sometimes superior) to those of Douglas-fir and these species are sometimes sold mixed.
Western larch lumber is dried according to end-use and customer specifications. Kiln drying inhibits natural staining of the wood, improves its strength and stiffness, enhances its appearance, and increases its resistance to decay and attack by insects.
| Physical Properties |
|---|
| Density (kg/m3) | Green | 549 |
| Air Dry | 600 |
| Specific Gravity (12% M.C.) | Standard | 0.55 |
| Hardness (N) | Side | 4210 |
| End | 5670 |
| MOE (Mpa) | Green | 11400 |
| Air Dry | 14300 |
| MOR (Mpa) | Green | 59.8 |
| Air Dry | 107.0 |
| Compression Parallel (Mpa) | Air Dry | 60.9 |
| compression Perpendicular (Mpa) | Air Dry | 7.31 |
| Shear (Mpa) | Air Dry | 9.25 |
| Cleavage (N/mm Width) | Air Dry | 48.0 |
Shrinkage
OD=oven dry
air=air dry 12% | Radial (OD) | 5.1% |
| Tangential (OD) | 8.9% |
| Volumetric (OD) | 14.0% |
| Volumetric (air) | 8.0% |
| Tang / Rad ratio | 1.8 |
Working Properties
Western larch wood is stiff, moderately strong and hard, as well as moderately heavy. The wood dries well, but with some tendency to warp and surface check. Works fairly readily with only a small blunting effect on cutting edges. It turns, planes and shapes well and can be sanded to a smooth finish. The wood glues well, has moderate nail and high screw holding ability, and takes a good finish.
| Process | Performance | Comments |
|---|
| Machining |
|---|
| Planing | Moderate | Recommended planer settings: 20o hook angle and 16 or 20 kmpi (knife marks per inch). |
| Turning | High to medium surface quality | Turns exceptionally well on a rotary-knife lathe. |
| Sawing | Easy to work with tools | Resin exudation can sometimes negatively affect blunting effect. |
| Boring | Good to moderate | Good boring quality with both brad point bits and moderate boring quality with single twist bits. |
| Mortising | Moderate | Good mortising quality when using a hollow chisel mortise. Common mortising defects: Splintering on the out-going side of the mortise and crushed grain inside the mortise. |
| Shaping | Good shaping quality | |
| Veneering | N/A | |
| Sanding | Good | Excellent sanding properties. |
| Fastening |
|---|
| Screwing | Good | Average screw retention: 547 lb. |
| Lateral Nail Holding | Good | Comparable to Douglas-fir. |
| Nail Retention | Excellent | Tends to split in nailing. Excellent holding once nailed. Surpasses Douglas-fir. |
| Gluing | Glues satisfactorily | Bonds well with a fairly wide range of adhesives under a moderately wide range of bonding conditions. |
| Finishing |
|---|
| Staining | Moderate | Wild grain is very visible when a dark stain is used. Resin content can make staining more difficult. |
| Painting | Average to good paint holding ability | Resin content can make painting more difficult if the resin is not set during drying. |
| Lacquering | Good | Recommend multiple clear coats or a high build clear finish to achieve smooth texture. Performed well in the tape test (i.e. edges of the cuts were completely smooth; none of the squares of the lattice was detached) and in the pull-off test (i.e. average strength of 29 kg/cm2). |
| Waxing | Good | Best results are obtained when using light- to medium-coloured waxes (e.g. Mellow Pine or Chestnut). |
| Drying |
|---|
| Ease of Drying | Moderately easy | Dries fairly well, but with some tendency to warp and surface check. |
| Durability |
|---|
| Natural Decay Resistance | Moderately durable | Should not be used in applications with prolonged ground contact. |
| Treatability | Impermeable to extremely impermeable | Can be improved by incising. |
Commercial Availability
Western larch is produced predominantly as Douglas-fir – Larch species mix in structural grades according to National Lumber Grades Authority (NLGA) rules for dimension lumber. Select Structural, #2 and better, and stud grades are the most common grades produced. Specialty in-house grades and export grades are also available. Lamstock is a common product for larch because of its high strength properties.
Appearance grades are also produced according to NLGA rules. Clears, shop lumber and moulding stock are most common, though there are many potential appearance grades that can be produced.
Sources
BC Wood Specialties Group, www.bcwood.com
Coast Forest Products Association, www.coastforest.org