SPF (Spruce-Pine-Fir) is a species group consisted of four species: White Spruce (Picea glauca), Engelmann Spruce (Pice aengelmannii), Lodgepole Pine (Pinus contorta), and Alpine Fir (Abies lasiocarpa). These species share similar characteristics, and are often traded jointly in market, hence the collective term SPF. The average height for this species group is 26m, with a maximal diameter of 80cm.
SPF is characteristic for its resistance to coldness, slow growth rate, small knots, and lightness in material. It produces lumber superior in straightness, smoothness, and glowing finish, ranging from white to light yellow in color. After proper drying, it can be processed into a wide variety of products, especially materials for slotting and drilling. Its great consistency also makes it suitable for nailing and paint coating. As such, the usage of SPF materials is very prominent and flexible, with particular emphasis on architecture and structural engineering due to its high durability. As one of the major species of North American lumber exports, its color and grain characteristics and flexibility are also reflected in other industrial uses.