The top surface of wood decks are often made from pressure treated wood. One example is YellaWood.2306.4 Plates, sills and sleepers. All foundation plates or sills and sleepers on a concrete or masonry slab, which is In direct contact with earth, and sills which rest on concrete or masonry foundations,[HIGHLIGHT] shall be treated wood [/HIGHLIGHT] or foundation redwood, all marked or branded by an approved agency. Foundation cedar or No. 2 Foundation redwood marked or branded by an approved agency may be used for sills in territories subject to moderate hazard, where termite damage is not frequent and when specifically approved by the building official. In territories where hazard of termite damage is slight, any species of wood permitted by this code may be used for sills when specifically approved by the building official.