Engineered Hardwood is also 100% wood. Its’ cross-ply construction allows installation below or above grade, even over concrete. It resists expansion and contraction caused by temperature and humidity changes. Engineered flooring is typically glued-down, stapled-down or floated over an existing floor. It is manufactured by permanently bonding together multiple layers of solid wood in a cross ply construction. Engineered hardwood is usually the only type of hardwood that is recommended for use below grade.