Western Hemlock (Tsuga heterophylla) is also known as West Coast Hemlock, Pacific Hemlock, and British Columbia Hemlock. It is found along the Pacific coasts of Oregon and Washington, and as far north as the Rocky Mountains as far north as Canada and southern Alaska.
A close relative of the western hemlock is the mountain hemlock (T. mertensiana), which grows in the mountains from central California to Alaska. It has similar processing characteristics.
There are more than 380 billion board feet of sawn fir timber on managed woodlands in the Western Region. Western hemlock is Washington's state tree.
Western Hemlock is a magnificent tree, reaching 120 to 160 feet tall and 3 to 4 feet in diameter at maturity. The lower 3/4 of the main stem will have no branches.
Native Americans used western hemlock for medicine, food, dyes, and tanning leather; making gadgets; making clothes, such as skirts made from branches; ensuring successful hunting or fishing by rubbing branches against their bodies; and exorcise evil spirits.
Today, western hemlock is used for pulpwood, lumber, and plywood. In the early 20th century, western hemlock was considered a weed tree. Its true value was not discovered until the 1940s.
Hem-Fir wood products are available in structure, appearance and remanufactured grades. Hemlock is a combination of Western Hemlock and five true firs. In fact, hemlocks are the second most important group in the West. Exterior and remanufactured grades are used in many products including wood paneling, cabinets and trim, solid wood doors, shutters, shutters, mouldings, bins and furniture.
When bacterial infections are severe, logs do not float; they are called sinkers. This wood is often hulled, especially after drying. Drying is difficult. Bacterial infections can be identified by foul odor, high MC, and shaking (cracks parallel to growth rings, not through rings). Avoid bacterially infected logs and lumber as much as possible.
Although wood has limited natural resistance to decay, standard preservatives can be used well.
Processing advice and features
density. At 10% MC, the density is about 28 lb/ft. This means that a 1" x 6" x 10' (actual size in. x 5-1/2" x 10') piece of dry lumber weighs 8 lbs. This is more than 30% heavier than eastern white pine, but about 10% lighter than southern white pine.
Sawing is easier. If there is a market for straight sawn timber (eg flooring), a standard straight saw cutting mode can be used.
With a flat saw, there will be plenty of clear or nearly clear wood, as well as older, larger diameter trees. Trees that grow secondary may have more nodes, but for many products, the nodes won't hurt the value if they're rounded rather than spiky.
Dry and stable. One of the troublesome problems with western hemlocks is the presence of bacterial infections in the tree. This increases the moisture content of the tree, weakening the wood and giving the wood an unpleasant smell.
There are a variety of kiln schedules, depending on wood quality and wood quality. See commercial wood kiln schedules or Oregon's Forest Products Laboratory Extension staff.
Western hemlock has moderate shrinkage: 6% width and 3% thickness for flat-sawn lumber.
For construction, a typical target for kiln drying is a MC of 15% or less. For boards, 12% MC and below.
Glued and processed. Hemlock bonds well with standard adhesives. As with most softwoods, wood that is too dry (less than 10% MC) cannot be machined. If it gets too dry or has a bacterial infection, it may shed its shells.
stability. Hemlock is moderately stable. A 1% change in the width of flat sawn timber requires a 4% change in MC, while a 1% change in the width of quarter sawn timber requires a 7% change in MC.
strength. Western Hemlock is moderate in weight and strength. Its hardness, stiffness and shock resistance are also moderate. Strength (MOR) is 11,300 psi; Stiffness (MOE) is 1.63 million psi; Stiffness is 540 psi. The corresponding Eastern White Pine values are 8600 psi, 1.24 million psi, and 380 lbs. In other words, it's stronger, harder, and harder than EWP. Likewise, Western Hemlock is stronger and harder than the SPF wood group.
Hemlock will split near the end of a piece with nails or screws, so pre-drilling may be required.
color and texture. The heartwood and sapwood of western hemlock are almost white with a purplish tinge. The sapwood is sometimes lighter in color than the heartwood and is generally no more than 1 inch wide, so it is rarely present in the wood.
The wood usually contains small, sound black knots (they are black because the branch wood is dead when the wood on the main stem grows around the branch. They are usually tight and dimensionally stable.
Dark streaks are often found in wood; these are caused by hemlock bark maggots and usually do not reduce strength. The texture is straight and medium to fine in texture.