Decking Decisions | This Old House.Good, lower-cost alternatives include appearance grade and, for dry areas, No. 1 select tight knot (STK). Use hot-dipped galvanized, aluminum or stainless-steel (ring-shanked) nails, screws and other fasteners. Cost: About $18 to $22 per square foot installed for both woods, not including substructure. Decking itself costs.