Pioneer Millworks Douglas fir Siding and Shiplap is an FSC® chain-of-custody certified, and a Pacific Northwest harvested option for wood in vertical applications. The rot resistance of Douglas fir and small tight knots, make it a favorite material choice for exterior applications. Our Douglas fir’s signature vertical grain has been brushed once allowing our standard color finishes to shine. Also available pre-primed for easy application of paint colors or unfinished to be stained on site. Shown here unfinished.