According to research by the Forest Products Laboratory in Madison, run by the USDA, a whole, unmilled tree can support 50 percent more weight than the largest piece of lumber milled from the same tree. So Mr. Gundersen uses small-diameter trees as rafters and framing in his airy structures, and big trees felled by wind, disease or insects as powerful columns and curving beams. picked by cecilberman 3 weeks ago