from WWPA's Hem-Fir Species Facts
published March, 1997
©1997 Western Wood Products Association
Range, growth habits and production
Characteristics & best uses
Factory and Shop products
Western Woods Region
Of the West's approximately 136 million acres of forested land, there are nearly 40 million acres of commercial timberland* and nearly 50 million acres of forested land, including some 13 million acres of designated "old growth," permanently set aside in parks, scenic reserves, wilderness areas, habitat reserves and research areas -- forever protected from harvesting. In addition, as of 1996, more than 80 percent of the forested area in the region's National Forests has been withdrawn from timber harvesting due to legislative, administrative, or judicial actions as even more progressive ecosystem management plans are implemented.
(*Timberland is forested area producing or capable of producing crops of industrial wood and not withdrawn from timber utilization by statute or administrative regulation. Any reference to standing volumes of sawtimber or acres of multiple-use timberland available for timber products in this text do not include any of the forested land that is permanently set aside, protected from harvesting.)
The Western Woods region is subjected to some of the toughest forest practice regulations in existence anywhere. In Western forests, growth exceeds harvest by more than 35 percent overall and by more than 50 percent in some areas. Refer to the section on "Environmental Performance" for additional information.
Hem-Fir species group
In the Western Woods region, the 12 contiguous Western states plus Alaska, there are approximately 20 commercially important species well suited to softwood lumber production. While each has unique characteristics, physical and mechanical working properties, making it appropriate for specific applications, these Western softwood species are grouped into six primary combinations. These combinations simplify production, inventories and distribution, and facilitate engineering and product specification for design.
Hem-Fir is a species combination of Western Hemlock (Tsuga heterophylla) and five of the True Firs: California Red Fir (Abies magnifica), Grand Fir (Abies grandis), Noble Fir (Abies procera), Pacific Silver Fir (Abies amabilis), and White Fir (Abies concolor). While Western Hemlock and the True Firs are sometimes marketed separately in products graded for appearance, these species share similar design values making products graded for structural applications interchangeable.
The Hem-Fir species combination is one of the most important in the Western region, second only to the Douglas Fir-Larch species group in terms of abundance, production volumes, strength, and versatility in end use.
Range, growth habits & production
In the West, the species in the Hem-Fir group commonly grow in intermingled stands along the Pacific Coast, from the Kenai Peninsula in Alaska to northwestern California. They also grow inland in a narrow, scattered pattern along the U.S.-Canadian border and then spread out fanlike to climb the mountain slopes of northeastern Washington, northern Idaho, northwestern Montana, and through the Selkirk Mountains of southeastern British Columbia. The largest stands are found in the humid, coastal mountains and on the western slopes of the Cascade Range in Oregon, Washington, British Columbia and Alaska. They thrive in this mild and humid climate, where frequent fogs and rain provide moisture during the growing season.
Western Hemlock, also known as West Coast Hemlock or Pacific Hemlock, was discovered by botanist Stephen L. Endlicher in 1847. He christened hemlock "tsuga." In Japanese, tsuga means "yew-leaved," referring to its short, flat -- and contrary to legend -- non-poisonous needles. Among the True Firs, White Fir was first discovered along the Columbia River in 1831 by Scottish botanist David Douglas. Douglas Fir (Pseudotsuga menziesii), which is not a fir at all but a distinct species, was named after this famous botanist.
Western Hemlock can be easily distinguished from other conifers in Western forests by its downward sweeping branches and drooping top. The needles have rounded tips and grow from the sides of the stems in pairs. Seed-bearing brown cones sprout at the ends of branch shoots. Like Douglas Fir, the lower branches of Western Hemlock die and fall away because of competition for sunlight. Thus, as the tree grows, it "prunes" itself and develops clear trunks up to three-quarters of its height. This natural characteristic is highly desirable in softwoods, as it leads to increased volumes of clear lumber in large logs.
Abundant in managed forests, it is estimated there are more than 380 billion board feet of Hem-Fir sawtimber on the managed timberlands of the Western region. Second only to Douglas Fir-Larch, Hem-Fir accounts for 28 percent of Western lumber production annually. This important species combination is nearly as versatile as Douglas Fir-Larch (which accounts for half of total Western production volume), lending itself to a variety of products.
Characteristics & best uses
In its unique way, Hem-Fir is a perfect combination of strength and extraordinary beauty and is quite literally one of the most handsome, elegant and versatile softwood species combinations on the market today.
Hem-Fir lumber is light and bright in color, varying from a creamy, nearly-white to a light, straw-brown color. It can be as light or lighter in color than some of the Western pines and is often considered, by those seeking a strong wood with a very light color, as the most desirable of the Western softwoods. Sometimes Western Hemlock may have a slight lavender cast, especially around the knots and in the transition area between the spring and summerwood growth rings. Attractive, delicate, dark grey or black streaks may be apparent in the wood. There is little variation in color between the heartwood and sapwood.
Hem-Fir lumber products are available in structural, appearance and remanufacturing grades. In strength properties, Western Hem-Fir is slightly below the Douglas Fir-Larch species combination, and above both the Douglas Fir-South and Spruce-Pine-Fir (South) species combinations. Hem-Fir is useful for a multitude of general-purpose framing applications and is capable of meeting the span requirements of many installations.
In the clear and nearly clear appearance grades, Hem-Fir "Finish & Select" products are fine grained and even textured, lending formality to wood paneling, cabinets and trim. Hem-Fir "Factory & Shop" grade products are remanufactured into handsome solid wood doors, louvers, shutters, moulding, case goods, furniture and more. Limited volumes of knotty, board products are available in Hem-Fir and these are graded primarily to the West Coast Lumber Inspection Bureau's "Alternate Board" grade rules, and to some extent to WWPA's rules for the "Common" grades. Lower-grade knotty products are useful for those utilitarian applications in construction where economy governs.
Preservative pressure-treated Hem-Fir products are both visually appealing and strong, and in comparison to the naturally durable Western cedars and redwoods, among the more economical species considerations for decks and other outdoor amenities. Among the Western species, Hem-Fir is a preferred species group for preservative pressure treating.
Recognized worldwide as a symbol of integrity, the Western Wood Products Association's grade stamp is a lumber buyer's guide to lumber satisfaction. This mark represents each WWPA Member mill's commitment to consistently deliver a product which meets uniform quality standards, whether the lumber is intended for structural or appearance purposes.
|Hem-Fir products carrying the WWPA certification mark are backed by the Association's quality control and inspection services, technical and field services, and the design and engineering data necessary to use Western lumber products in construction. WWPA is the only Western lumber association that provides this level of product support to the buyers of its Member companies' grademarked lumber. |
Lumber grades are divided into three basic categories:
Moisture content, seasoning & marketplace preferences
"Green" lumber is unseasoned lumber. It is gradestamped as "S-GRN" and has a moisture content (MC) level above 19 percent at the time of surfacing. The same design values apply to both S-GRN (unseasoned) and dry lumber. However, the term "dry" can be confusing in lumber terminology.
In general, "DRY" indicates a product was either air-seasoned or kiln-dried to 19 percent or less moisture content at the time of surfacing. S-DRY can mean kiln dried or air seasoned, while KD specifically means kiln dried. The moisture content level of DRY lumber is further qualified depending on the general classification (i.e. structural- or appearance-grade categories), the grading rules for specific grades (e.g. MC for "Finish & Select" grades is specifically qualified), and/or by the specific terms of buyer/seller agreements.
In structural grades, DRY indicates a product was either air- or kiln-dried to 19 percent or less MC at the time of surfacing. It will be stamped S-DRY or, if kiln dried, KD or KD-HT. Any lumber surfaced at a moisture content level of 15 percent or less may be stamped MC15, or if kiln dried, KD15.
Historical practices and regional market preferences influence the availability of structural framing lumber at certain moisture content levels. Over time, certain regions evolved as "green markets," with a preference for S-GRN products such as Douglas Fir-Larch framing lumber, while other areas evolved as "dry markets" for such products as S-DRY or KD Hem-Fir.
Historically, Hem-Fir products were shipped to inland U.S. markets and Western lumber manufacturers dried their Hem-Fir prior to surfacing in order to reduce its weight for overland transporting. Over time, builders began to like these dry framing products and, as a result, certain areas became dry markets for Hem-Fir.
Tradition continues to influence current practices for Hem-Fir manufacturing. Approximately 80 percent of Western Hem-Fir framing products are manufactured and shipped either S-DRY, KD or KD-HT. Dry Hem-Fir performs well and historical production practices have led to today's wide availability of Hem-Fir in dry STUD and other Dimension and special Dimension lumber grades.
In appearance-grade products, the term DRY indicates a product was either air- or kiln- dried to 19 percent or less moisture content in the Alternate Board and Common grades. However, due to marketplace preferences, these products are occasionally manufactured and shipped by WWPA mills at lower moisture-content levels. If dried to 15 percent or less moisture content, these grades can be gradestamped (on either wide face or the ends) MC15 or KD15, as appropriate. In the clear and nearly-clear high-end appearance-grade products, such as the Finish & Select grades, DRY specifically means a maximum of 15 percent moisture content.
In addition, as specified in WWPA's Western Lumber Grading Rules, 85 percent of the items in Finish & Select grades are shipped with a MC level of 12 percent or less. Often the highest-quality, appearance-grade products are not gradestamped to avoid marring the beauty of the wood. In these cases, grade and moisture-content information is included in the written documentation accompanying products.
For millwork, remanufacturing applications or glued products, Hem-Fir is seasoned in temperature- and humidity-controlled dry kilns or stickered and air dried until its moisture content reaches the desired level for the intended purpose -- a level often set by the buyer. Unless specified otherwise by agreement, Western Hem-Fir production in the Factory & Shop grades is shipped at MC15 or KD15, with 85 percent of the items at 12 percent or less MC.
Since Hem-Fir framing lumber products are nearly as strong as Douglas Fir-Larch, they can meet many of the structural load-bearing and load-carrying requirements of residential, light commercial and heavy construction. With their good strength and stiffness properties, S-DRY and KD Hem-Fir structural-grade products are well suited to framing systems where solid-sawn, structural lumber is needed for immediate use in an assembly of other dry framing products (I-beams, structural-glued finger-jointed lumber, stress-rated boards, etc.). Dry Hem-Fir framing products are subject to minimal shrinkage and checking, and thus perform extremely well in hot, dry climates, or in cold, low-humidity climates, and in multistory framing.
Recently, in some regions of the U.S., end users have experienced "bouncy" floors when imported species have been used to their maximum allowable published spans. In contrast, published design values for all U.S. species combinations have proven reliable in end use and U.S. species perform well to published allowable maximum spans. Hem-Fir's modulus of elasticity (MOE or E) value, a stiffness factor in floor systems, exceeds all other Western species combinations except Douglas Fir-Larch, the species combination which is held as the standard against which all other framing lumber is measured worldwide. It is the combination of stiffness (MOE value) and strength (Fb value) that yields a satisfactory floor system.
Hem-Fir is additionally preferred by many builders because of its: resistance to splitting in nailing and screwing; ability to hold nails and screws securely; ease of sawing without splintering; ability to hold a variety of glues and adhesives; and moderate lightness in weight. It is straight grained, stiff, strong, easy to work and relatively free from pitch.
Dimension Lumber: The bulk of S-DRY and KD Hem-Fir is produced in Dimension lumber sizes (2" to 4" thick by 2" and wider). Dimension lumber Hem-Fir products include:
Structural Light Framing grades fit applications where high design values are needed in light-framing sizes for engineered applications, trusses, laminated products and multistory projects. (grades include SELECT STRUCTURAL, NO. 1&BTR, NO. 1, NO. 2, and NO. 3.) These grades may be a special order for some retail lumber suppliers.
Light Framing grades are intended for general framing applications such as wall framing, plates, sills, cripples, blocking, etc. (CONSTRUCTION, STANDARD, and UTILITY).
STUD grade is intended for vertical installations in wall systems and other applications including blocking and furring.
Structural Joists & Planks, in 2x5 through 4x18 sizes (with the majority of production in 2x6 through 4x12), are available in SELECT STRUCTURAL, NO. 1&BTR J&P, NO. 1, NO. 2 and NO. 3 to fit engineered applications where larger-sized members are required.
Special Dimension: Hem-Fir products in this category include Machine Stress-Rated (MSR) lumber for components manufacturing and engineered applications, and structural-glued (end- or fingerjointed) products,which are recognized by U.S. building codes as interchangeable with solid-sawn lumber products of the same grade, species and intended end use.
One quarter of the lumber used in components and truss manufacturing is MSR lumber. Hem-Fir MSR products are commonly available in several stress levels, occasionally up to 2400 Fb-2.0E. These MSR products offer good strength-to-weight properties, recognized plate-holding ability, exceptional stiffness and consistent availability in a variety of lengths, widths and grades.
Hem-Fir is ideally suited for structural-glued products. The USDA Forest Products Laboratory rates Hem-Fir in the top group of softwoods for ease of gluing, based on glueability under varying conditions and with different types of adhesives. This, along with Hem-Fir's inherent strength properties, make the species combination a natural for end- or finger-jointed, edge- and face-glued structural products. And because of its beauty, it's a natural for finger-jointed millwork and mouldings, edge- and face-glued boards, and laminated stock. These products make excellent use of short lengths, thus increasing utilization of available timber resources. WWPA provides testing and quality control for glued products, currently certifying the manufacture of Hem-Fir structural-glued Dimension lumber and board products under the following classifications: Light Framing and Studs, Structural Light Framing, Structural Decking, Stress-Rated Boards, and Structural Joists and Planks.
Larger sizes: The bulk of production in the larger sizes is manufactured and shipped S-GRN. Hem-Fir products in the 5" & thicker and 5x5 & larger sizes of Beams & Stringers and Posts & Timbers are unique products well suited to meet specific design criteria.
(Refer to WWPA's Western Lumber Product Use Manual for additional design information, to the Structural-Glued and MSR Technical Information Product Sheets for information on these products, and to WWPA's Vol. 1 Species Book: Dimension Lumber for color photographs of structural grades.)
Hem-Fir is a discerning selection for exposed ceilings and a practical choice for roofing, flooring or subflooring. Of the many products available in Hem-Fir, Structural Decking truly showcases Hem-Fir's combination of strength and beauty. These products, which are also known as "roof decking," are 2" to 4" thick by 4" & wider in width and available in two grades: SELECTED DECKING (for fine visual aesthetics) and COMMERCIAL DECKING (when appearance is less important).
SELECTED DECKING can be used so that the face, or better side, will show the sophisticated, casual elegance of Hem-Fir in applications such as exposed ceilings. Its moderately light weight makes it easy to handle and install. Hem-Fir is usually run to standard decking patterns, in nominal 2" and 3" single tongue-and-groove (T&G), and is available with V or rounded edges. While SELECTED DECKING is a structural-grade product, some WWPA Member mills provide a proprietary variation of this product through buyer/seller agreement. These proprietary products give consideration to appearance characteristics in order to meet discriminating architectural requirements and/or a specification for MC15 or KD15 in a 2x structural-grade product. As with any product to be used in a T&G application, it should be acclimated to the surrounding atmosphere prior to installation.
COMMERCIAL DECKING is ideally suited for subflooring in both solid-sawn and structural-glued products. Because Hem-Fir is nearly as strong as Douglas Fir-Larch in extreme fiber stress in bending (Fb)and modulus of elasticity (E or MOE), it can meet engineering requirements for many structural decking installations. Some T&G decking is manufactured to pattern from NO.2 & BTR or No.3, 2x6 or 2x8 framing lumber. These products are generally used for concealed subfloors in deck and girder construction.
In products graded for appearance, wood-savvy architects and designers often choose Hem-Fir for trim, fascia, paneling, moulding and millwork, as well as for exposed wood ceilings. Substantial volumes are available in the clear and nearly-clear appearance grades and whether used extensively, such as for paneling, or in small decorative elements, Hem-Fir boasts remarkable versatility and usefulness. It compliments many architectural styles and design themes.
When acclimated prior to installation, MC15 or KD15 Hem-Fir products retain their shape and size without shrinking, swelling, cupping, warping, bowing or twisting. Adding to its aesthetic qualities, Hem-Fir, like all wood, is a very good insulating material. It has a coefficient of heat transmission, or K value, of .89 BTU per inch of net thickness at 12 percent moisture content, which puts it among the best species for insulating properties.
Interior designers often like Hem-Fir for two primary reasons: its color and natural resistance to darkening from exposure to light. While all wood darkens over time with exposure to sunlight, Hem-Fir often remains true to its original, freshly-milled pastel color.
Finish carpenters, remanufacturers and woodworkers like Hem-Fir for other reasons. The straight grain and fine texture sands to a silky, reflective smoothness with virtually no tendency to split. Hem-Fir yields clean, straight edges and accurate contours with either machine or hand tools, and can be worked easily by either. The wood grips fasteners securely and accepts adhesives without a problem. It readily accepts finishes, ranging from clear coatings, transparent lacquer, varnishes, oils or wax to a full selection of stains and bright or subdued tints or paints.
The clear and nearly-clear products dominate the appearance grades in Hem-Fir. The highest grade categories, Finish & Selects, may be specified in either vertical or flat grain. If grain pattern is not specified, these grades will be shipped as a combination of vertical and flat grain. These high-appearance Western lumber products include Selects (B & BTR SELECT, C SELECT and D SELECT) and Finish(SUPERIOR, PRIME, E). Such products are recommended for interior wall and ceiling paneling, trim and cabinet work with either natural, stain, or enamel finishes that respect their fine appearance. These products may be wrapped at the mill for protection in shipping and handling.
Most of the knotty fiber in Hem-Fir is generally manufactured into structural products whenever possible. However, some knotty, appearance-grade products are manufactured in Hem-Fir. These products are manufactured and shipped about half and half in S-GRN and S-DRY and are intended more for general construction applications than fine interior installations.
For the most part, the general-purpose, knotty-appearance grades in Hem-Fir are manufactured, by tradition, in the Alternate Board grades of the West Coast Lumber Inspection Bureau's (WCLIB) grading rules. These grades include SELECT MERCHANTABLE (used primarily in housing and light construction for soffits and fascia, and occasionally for shelving where sound, tight knots are acceptable), CONSTRUCTION and STANDARD (for general construction purposes and serviceability in sub-floors, roof, wall sheathing, and let-in bracing), and UTILITY and ECONOMY (for use in applications where economy is the basic requirement).
(Refer to WWPA's Vol. 2 Species Book: Boards and Commons for additional information and color photographs of appearance grades in a variety of Western softwood species.)
The clear and nearly-clear paneling products available in Hem-Fir give a stunning, soft glow to ceiling and wall paneling in traditional and contemporary homes as well as a subtle, sophisticated ambience in family and living rooms, dens, bedrooms, and kitchens. Because Hem-Fir has a flame-spread rating of 73, it qualifies for a Class 2 (or B) rating. Consequently, it is frequently specified as paneling in public buildings such as theaters, shopping centers and restaurants. Europeans have made Hem-Fir a popular choice for paneling because of its uniform tone, luster and hardness.
Like all patterned products, solid wood paneling products reflect the grade of their starting, appearance-grade material (as described above), adhering to similar requirements for permissible characteristics. In most cases, paneling products in Hem-Fir will be run-to-pattern from the exquisitely beautiful, clear and nearly-clear Finish & Select grades and are available in a variety of patterns. Whereas several grades of knotty paneling products are widely available in the Western pines, knotty grades in Hem-Fir are not commonly remanufactured into paneling products.
(Refer to WWPA's Standard for dimensioned profiles of run-to-pattern products and to the TIP Sheet on Flame-Spread Ratings for additional information.)
Factory and shop products
Lumber intended for trim and other non-structural applications may be from the appearance category of grades, as described earlier. Or, if intended to be run-to-pattern or further manufactured into specialty wood products, it may be from the Factory & Shop category of grades. These MC15 and KD15 Hem-Fir products are available in a variety grades for such end uses as mouldings, doors, windows, case goods, etc. This category of lumber products, which is graded to be re-cut for the recovery of clear pieces in pre-determined sizes, is usually available only in large volumes, mill direct to remanufacturers.
Owing to its unique combination of attributes, Hem-Fir is a dominant species combination for manufactured woodwork. It is readily and accurately milled to sharp detail. Its smooth surfaces and high dimensional stability assure continuing fine appearance over time. Hem-Fir moldings and interior trim do not splinter, are resistant to scuffing and the effects of use over time, and the color tones remain light.
On the West Coast of the U.S., residential baseboard and door-jamb mouldings are more often manufactured from Hem-Fir than any other species. Hem-Fir mouldings come in a wide choice of attractive patterns and varying lengths. Stair components made from Hem-Fir are exceptionally hard wearing and will readily take paint or stain finishes. And because it can be machined easily with exact precision, a number of decorative items are also made from Hem-Fir: turned and worked cornices, crown mouldings, shutters, louvers, blinds, ornamental trim pieces, furniture and cabinets, wine and spice racks, knife holders, serving trays, cutting boards and more.
Hem-Fir is readily pressure treated with preservatives. Such products, generally in Dimension lumber grades and sizes, are widely used for backyard outdoor decks. Treated Hem-Fir is easily stained to resemble cedar or redwood, or it may be given a clear protective finish to enhance its natural color. It is a preferred Western species group for preservative pressure treating. Because of its combination of strength properties and beauty, this species combination is useful for both the load-bearing as well as non-structural components of outdoor installations. It is also very abundant which makes it more cost competitive than the naturally durable species. With incising (small cuts are made in the surface of the wood before treating), Hem-Fir may be treated to appropriate retention levels for above-ground, ground-contact, or in-ground installations.
The American Wood Preservers Association (AWPA) provides treating standards and retention levels for a number of preservative and fire-retardant chemicals. All pressure-treated wood should bear the mark of a quality control agency approved by the American Lumber Standard Committee. Chemical retention is stated in terms of the weight of the chemical retained (in pounds) per cubic foot (pcf) of wood after treatment; the larger the number, the more chemical retained. In general, relevant AWPA standards and retention levels for waterborne preservatives are:
0.25 pcf to AWPA Standard C-2 is required when the product is used above ground;
0.40 pcf to AWPA Standard C-2 is required if the lumber is in contact with soil or fresh water;
0.60 pcf to AWPA Standard C-15 is required of the lumber is used as a permanent wood foundation.
For more information, contact the Western Wood Preservers Institute.
The WWPA grademark identifies Western lumber products backed with assurances for quality, performance and technical support. WWPA maintains a team of lumber inspectors throughout the Western region to monitor the grading and quality control of Western lumber products from WWPA Member mills, ensuring products consistently meet grade specifications. Additionally, WWPA has technical experts on staff with training and work experience in design, engineering, lumber specifications, code conformance, construction, manufacturing, wood technology and forestry. From the Association's headquarters, these experts offer technical assistance in all aspects of Western lumber end use for WWPA Member company products.
To order a full-color version of this publication, complete with photos and examples of grades, or any other WWPA title referred in this text, go to the WWPA Online Store.
For a list of WWPA Member mills that produce Hem-Fir lumber products, go to the WWPA Online Buyers' Guide section.