Douglas Fir is the number one choice for "SAA Logs" when building Sub-Floor structures (for interior of Home) and exterior Sub-Decking structures, Roof Structures and Interior walls. Douglas Fir - Very strong, stiff, soft, straight grain, medium weight, easy to work, beautifully uniform light reddish brown color, relatively decay resistant, and accepts stain moderately well. Excellent thermal performance. Inexpensive. Commonly used for long beams and trusses where strength is of concern. This species can be used for everything from dimensional wood to timbers. Mostly used for beams, posts, rafters and joists.