Western hemlock

Category: Softwood
Region: Coast, Interior
Title: Western hemlock (Tsuga heterophylla)

Photo credit: Kristin Charleton, Sundew Media

Western hemlock grows along B.C.’s coast on both the east and west sides of the Coast Range as well as in the interior wet belt west of the Rocky Mountains. It is a large tree that typically grows 30 to 50 metres and has conspicuously drooping new growth at its top. Western hemlock is used for general construction, roof decking and plywood, as well as for laminating stock and the production of glue-laminated and solid beams. Its strength and stiffness make it a preferred material for use in horizontal components and longer spans.

Western hemlock is the most plentiful tree species on the coast of B.C. It is commonly sold and shipped with amabilis fir under the name hem-fir, which has an extremely wide range of uses because it offers good strength, appearance and working qualities.

Where it grows

Western hemlock is the single most plentiful tree species on B.C.’s coast. It grows along both the east and west sides of the Coast Range, from sea level to mid-elevations, as well as in the interior wet belt west of the Rocky Mountains.

Western hemlock seldom grows in pure stands and is instead usually mixed with Douglas-fir, amablis fir, Sitka spruce, and western red cedar. Its shallow root system makes it susceptible to windthrow or wildfire. Occasionally it develops in pure stands after a wind has blown over many trees. Western hemlock tolerates shade and grows abundantly underneath mature trees.

Did you know?

Hemlock was named after a European weed that has a similar smell. Western hemlock is not related to poison-hemlock, the weed that killed Socrates.

Western hemlock species distribution map

Identifiable characteristics

Western hemlock is a large tree that typically grows 30 to 50 metres tall and 1 to 1.5 metres in diameter. It usually lives about 500 years. The tree has a rather narrow crown with conspicuously drooping new growth at the top. It has mostly down-sweeping branches and delicate feathery foliage. The bark is dark brown to reddish-brown, becoming thick and strongly grooved with age.

The needles are nearly flat, glossy and soft. They are yellow to dark green on the upper surface and whitish underneath. They are unequal in length and produce feathery flat sprays. The small, numerous seed cones are greenish to reddish-purple and turn brown with age.

Photo credit: Kristin Charleton, Sundew Media

Close up image of Western Hemlock (Tsuga heterophylla) bark on a live tree

Common uses and applications

Western hemlock and amabilis fir are nearly identical in appearance and physical properties so they are commonly sold and shipped together under the name hem-fir. Trees of both species are shade-tolerant and prune themselves as they grow to produce a tall, branch-free trunk. In dense stands they may have a clear stem for three-quarters of their height, a natural growth characteristic that produces large amounts of clear and factory lumber from the log.

Western hemlock is used for general construction, roof decking and plywood, as well as for laminating stock and the production of glue-laminated and solid beams. Compared to other species, its strength and stiffness make it a preferred material for use in horizontal components and longer spans. Hemlock timbers are often treated for railway ties.

Western hemlock’s excellent working properties make it the first choice for mouldings and interior woodworking. It is widely used in joints, veneered interior panelling, furniture, doors, floors and windows, and is also used for pulp and newsprint.

Indigenous Peoples carve hemlock to make spoons, combs, roasting spits and other implements. Hemlock roots are sometimes spliced into bull kelp dishing lines to strengthen them. Hemlock bark is rich in tannin and is used as a stain to treat wood and a dye to colour wool and other textiles.

 

Sunny daytime view of bedroom showing beautiful western hemlock (Tsuga heterophylla) bed frame and night stands

Commercial properties

Western hemlock has a relatively good strength-to-weight ratio and is known for its working properties. The wood requires special care when drying but yields a quality product. Its even density provides for excellent machining properties. It turns, planes and shapes well and can be sanded to a smooth finish.

It is non-resinous and takes any stains or finishes extremely well. It sands smoothly, glues easily and has a high nail and screw holding ability.

Photo credit: Michael Bednar

Western hemlock dimension lumber

Commercial availability

Western hemlock is commonly sold and shipped together with amabilis fir under the commercial designation hem-fir (also often referred to as hem-bal). Hem-fir is primarily available as structural lumber for North America, Japan and other export markets.

In North America, structural grades are in accordance with the National Lumber Grades Authority (NLGA) rules for dimension lumber. Select Structural, #2 and better, and stud grades are the most common grades produced for North America, with squares being the most common Japanese product. Specialty in-house grades, lamstock and export grades such as E-120 for Japan are also marketed.

Appearance grades are produced according to NLGA rules. The most common are clears, shop lumber and moulding stock, although many potential appearance grades can be produced.

Western hemlock 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.

Photo credit: Michael Bednar

Palettized, banded, and stamped Western hemlock dimension lumber ready for shipment

Western hemlock – physical properties

Density (kg/m3)Green420
Air dry429
Specific gravity (12% m.c.)Standard0.42
Hardness (N)Side2740
End4410
MOE (Mpa)Green10200
Air dry12300
MOR (Mpa)Green48.0
Air dry81.1
Compression parallel (Mpa)Air dry46.7
Compression perpendicular (Mpa)Air dry4.53
Shear (Mpa)Air dry6.48
Cleavage (N/mm width)Air dry37.5
Shrinkage
OD = oven dry
air = air dry 12%		Radial (OD)5.4%
Tangential (OD)8.5%
Volumetric (OD)13%
Volumetric (air)8.1%
Tang / rad ratio1.6

Western hemlock – visual properties

Colour
HeartwoodPale brown with a purplish tinge.
SapwoodNearly white to pale brown.
Heartwood / sapwood contrastThe sapwood, which is sometimes lighter in colour than the heartwood, is generally not more than 2.5 cm wide.
Latewood / earlywood contrastGrowth-rings are less prominent than those of
Douglas-fir. The darker-coloured latewood bands have a reddish or purple cast and are distinct from the earlywood.
Grain
Wood is straight-grained, fairly even in texture, and somewhat lustrous.
Figure
Plainsawn lumber or rotary-cut veneer: distinct, inconspicuous growth ring.
Quartersawn lumber or quarter-sliced veneer: faint growth ring stripe.
Knots
Contains small, sound black knots that are usually tight and dimensionally stable.
Other
Wood is non-resinous.
“Birdpecks”, or small bark pockets, and dark streaks are often found in the lumber. May contain ring shake.

Western hemlock – working properties

ProcessPerformanceComments
Machining
PlaningFair to good resultsTypical defects: fuzzy grain, raised grain, and chip marks.
TurningGood surface qualityEasy. Good results.
SawingEasy to difficultVaries from difficult to easy. Slight to moderate blunting effect.
BoringGoodResponds well to boring operations.
MortisingGoodEasy. Finishes well.
ShapingModerate shaping qualityEasy, with moderate surface quality.
VeneeringGood
SandingGoodGood sanding finish.
Fastening
ScrewingModerateIntermediate holding. Tendency to split. Good results if pre-drilled. Average screw retention: 470 lb.
Nail retention Good
Lateral nail holdingGoodTendency to split.
GluingGlues satisfactory
Finishing
StainingAverage to goodOld-growth: smooth texture achieved. As stain gets darker, prominent wild grain is visible. A wash coat would even out the colour. Second-growth: Stainability is average for light colours, poor for dark. Best finish is with light stain or clear finish followed by nitrocellulose alkyd clear sealer and finish.
PaintingAverage to good paint holding abilitySatisfactory paint holding ability.
LacqueringGoodOld-growth: natural finish (clear coat) looks best. Satisfactory results. Second-growth: excellent results with clear coat.
WaxingGoodGood results. Best results are obtained when using light coloured waxes (e.g. mellow pine).
Drying
Ease of dryingModerately easy to moderately difficultThere is a wide variation in the moisture content of green western hemlock. Best results are obtained when sorting by moisture content is done. Due to the high moisture content of this wood, longer kiln drying times are required. When dried at high temperatures sapwood can turn a brownish colour.
Durability
Natural decay resistanceSlightly durableNot appropriate for prolonged outdoor exposure.
TreatabilityImpermeableCan be improved by incising.

Data for these property tables has been compiled by FPInnovations from internal and external scientific sources.
FPInnovations is a not-for-profit technical research institute serving the Canadian forest sector.

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