Even if your residential or commercial property currently has concrete floors, it is still possible to fulfill your dream of a hardwood floor. Installing hardwood over concrete will take considerable work, but it can be done.
1.) Checking For Moisture: Installing hardwood over moist concrete will cause problems later on. To check for moisture on light colored slab, place a rubber mat on the concrete floor and place a weight over it. After 24 hours, if the concrete under the rubber mat shows dark spots, too much moisture is present. For darker slabs, you should tape a square foot of clear polyethylene film over the slab, making sure to seal off the edges. If condensation collects under the film during the 24-hour wait, too much moisture is present.
2.) Remove Moisture: If moisture on your flooring exists, remove it using a industrial-grade humidifier and heat. If possible, turn up the heat in the space to 80 to 85 degrees for 48 hours. Repeat the test (see #1) after this period to validate if there's still moisture.
3.) Repeat Until Dry: Do these tests in several areas of the room, multiple times.
1.) Prime the Surface: Prime the slab and apply cold, cut-back asphalt mastic with a notched trowel at the rate of 1 square meter per liter. Allow to set for two hours.
2.) Purchase and Roll the Underlayment: Unroll 15 lb. asphalt felt or building paper, lapping the edges 4" and butting the ends.
3.) Rinse and Repeat: Apply a second similar coating of mastic and roll out a second layer of asphalt felt or paper in the same direction as the first, staggering the overlaps to achieve an even thickness.
1.) Cover the Concrete: Where humidity and temperature are steady, cover the entire slab with 4 to 6 mm of polyethylene film, overlapping the edges 4 to 6", and allowing enough film to extend under the baseboard on all sides.
2.) Remove Moisture: Where moisture conditions are higher than average, prime the slab and apply cold, cut-back mastic with a straightedge or fine-tooth trowel (2 square meters per liter). Allow to dry for at least 90 minutes.
3.) Lay the Poly: Unroll the polyethylene film over the slab, overlapping the edges 4 to 6 inches (10 to 15 cm).
1.) Add the Vapor Retarders: Roll the film flat on every square centimeter to insure proper adhesion. Bubbles should be punctured to release trapped air.
2.) Install Plywood: Install the plywood after the asphalt felt or plyethylene is in place. Loosely lay a nailing surface of 3/4" x 4' x 8' exterior plywood panels over the entire area, but be sure to leave a 3/4" space at the wall line, and 1/5" - 1/2" between panels. Where a finish trim will not be used (doorjambs, etc) it is recommended to cut plywood to fit within 1/8". The best way to prevent cracks along panel edges is to lay the plywood diagonally, across the direction of the finished floor .
3.) Consider the Room's Layout: If the slab does not have radiant heat pipes installed, then fasten plywood to the slab with power-actuated fasteners. Secure the center of the panel first and then do edges, using nine or more nails. If the slab does have radiant heat pipes, cut the ply- wood into 2'"by 8" planks, score the backs (3/8" deep on a 12" grid is recommended), and lay the panels in a staggered pattern. Plywood planks may be glued to the plastic with asphalt mastic if the system being used is not radiant heat.