Dry Rot, decay of seasoned wood caused by the attacks of any of a number of species of fungi. These fungi penetrate to the interior of timbers and consume the cellulose in the wood fibers, leaving the timbers porous, although the wood may appear sound on the surface. The decay, dry rot, is so called because of the powdery appearance of the decayed wood, but the term is misleading because the fungi need water to live, and dry rot appears only in wood that has been exposed to moisture. The best method of preventing dry rot in any type of wood construction is to avoid dampness. If dampness is unavoidable, as in outdoor construction, creosote or other substances may be used to protect timbers.