Douglas Fir-Western Larch (DF-L)
This species combination has the highest modulus of elasticity (MOE or E) value (the stiffness factor in floor systems) of all North American softwoods. In strength properties, DF-L has the highest ratings of any Western softwood for fiber stress in bending, tension parallel to grain, horizontal shear, compression perpendicular and compression parallel to grain.
Douglas Fir (DF) is often the standard against which all other framing species are measured. Its strength combined with a superior strength-to-weight ratio, high specific gravity (for excellent nail and plate-holding capability), excellent dimensional stability (giving “green” DF products the ability to season well in position), the moderate decay resistance of its heartwood, and documented excellent performance record against strong forces resulting from winds, storms and earthquakes, have given Douglas Fir its reputation. It is also tight knotted and close grained, adding the bonus of beauty to its structural capabilities. Color, grain pattern, texture, knot size and type are addressed in the rules for appearance grades.
Douglas Fir is the lead species for the West, with more volume shipped than any other species, and its sterling performance history is recognized the world over. It is abundant and widely available in second and third-growth stands yielding products in multiple grade classifications: dimension and other framing products, engineered structural products such as MSR, finger-jointed, and glu-lam products, high (clear) to low (economy) grade appearance products, and industrial and specialty grades. DF doors, manufactured from products in the Factory & Shop grade classification, are renowned for their beauty and performance.
Douglas Fir’s light rosy color is set off by its remarkably straight and handsome grain pattern. Sapwood is white to pale yellow; heartwood is russet with high contrast between the springwood and summerwood. While similar, Western Larch is slightly darker in color, with the heartwood being a reddish brown and the sapwood a straw brown.
Douglas Fir grows throughout Western forests with the most abundant region being in the coastal climates of Oregon, Washington and northern California. In the Inland Region, east of the crest of the Cascade Mountains, Douglas Fir and Western Larch often grow in intermixed stands. Usually marketed separately in the appearance grades to provide more options for the marketplace, coastal and inland Douglas Fir and Western Larch share similar structural performance characteristics and are often combined in dimension lumber structural products. While DF products from the various parts of the vast Western Region are virtually indistinguishable in terms of appearance, the growing conditions of different parts of the region contribute to the physical working properties of the species. Consequently, Douglas Fir’s growing region is identified in the grade stamp. Douglas Fir from the US coastal and inland regions is designated as DF, or when combined with Western Larch as DF-L. (Canadian DF products are identified as DF-North.) Douglas Fir originating from Arizona, Colorado, Nevada, New Mexico and Utah is designated as DF-S. Coastal DF represents 73%, inland DF-L represents 26%, and DF-S represents 1% of the species’ production in the Western U.S.
There is no such thing as a Hem-Fir tree; it doesn’t exist. Hem-Fir is a species combination of Western Hemlock and the true firs (Noble, California Red, Grand, Pacific Silver and White fir). Being only slightly below DF-L (and above DF-S) in strength properties, this is an extremely versatile species group and useful for multiple, general-purpose framing applications. In the structural framing grades, Hem-Fir is capable of meeting the span requirements of many installations.
Hem-Fir is often considered by those seeking wood with a very light color as the most desirable of the Western softwoods. It is as light or lighter in color than some of the Western pines but stronger. Products are available in structural, appearance and remanufacturing grades. It is easily pressure treated with preservatives, making it useful for decks and other outdoor amenities.
Hem-Fir products are white to a light straw color, sometimes with a slight lavender cast, especially around the knots and in the transition area between the spring and summerwood’s growth rings. The heartwood is not distinct. Sometimes small, delicate dark grey or black streaks appear in the wood. Hem-Fir is fine grained and even textured, with a refined appearance. In the clear and nearly clear appearance grades, these products lend formality to wood interiors. Hem-Fir is often specified for high quality case goods, doors, moldings and millwork.