How to Install Hardwood Flooring on a Concrete Slab Hardwood flooring is one of the hallmarks of quality construction. Craftsmanship and materials are clearly exposed to inspection, and few aspects of the home are as high in consumer appeal. That's why experienced builders pay close attention to minimizing expansion and contraction when preparing to install this traditional material, especially in concrete slab construction. Below-grade installation is not recommended. The slab must be flat and level with a trowel finish, free of grease, oil, stains and dust.
New concrete is heavy with moisture, so test for dryness before beginning the subfloor.
Allow to set for two hours. Over this, apply a second similar coating of mastic and roll out a second layer of asphalt or paper in the same direction as the first, staggering the overlaps to achieve an even thickness. Puncture bubbles to release trapped air. Install the plywood after the vapor barrier is in place. Lay plywood diagonally across the direction of the finished floor to help prevent cracks along panel edges.