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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.
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