Engineered wood flooring is the best choice when installing below grade (in a basement) or over a concrete slab. However, traditional 3/4″ thick solid wood floor works great above grade, and in some cases may be used on concrete slabs (not in a basement) when glued down and used with appropriate moisture barriers. (To be sure you can glue your floor to concrete, verify with the flooring manufacturer and glue manufacturer.) Solid wood flooring should not be installed over radiant heat systems, but many engineered floors are compatible with radiant heat.