Douglas Fir-Larch (DF-L)

This species combination has the highest modulus of elasticity (MOE or E) value (the stiffness factor) 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 metal truss plate-holding capability), excellent dimensional stability (giving "green" DF products the ability to season well in service), 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, knot size and type are addressed in the rules for appearance grades.