Fitting & Nailing Hardwood
Hardwood floor installation requires some basic carpentry skills and some specialized tools like a floor nailer (rental item), miter & jamb saws.
Remove the baseboards (try to avoid breaking them unless planning to replace them). Most installers recommend putting down a 6 mil poly plastic or 15 lb. builder's felt vapor barrier.
Overlap the edges about 4" to 6", glue down the seams with tape or tar mastic, and avoid tearing the material during installation.
Often, flooring is laid out so it's parallel to the longest outside wall. However, every situation is a little different, so you'll have to evaluate the layout to coordinate with the room's visual focal point.
If you can't decide on the layout, dry-fit several courses in each direction to see how they will look and fit.
Lay longer pieces at entries/doorways when working with random lengths. Integrate short pieces throughout the floor, but avoid clustering them together.
Insert spacers around the perimeter of the room to create an expansion gap for the flooring. The gap will hide under the baseboard, but will allow the boards to expand/contract.
Slide the first course of planks into position with the groove side against the wall. You may need to set up a stringline to get the first row started straight if the wall is crooked.
Nail through the face of the course so it will hide under the baseboard and also angle a nail over the tongue (called blind nailing) every 10" to 12" for strips and 6" to 8" for planks. Nails should be long enough to penetrate the subfloor by at least 1".
Tap following courses into place with a scrap piece, staggering rows so seams aren't continuous across the floor. Use a pneumatic floor nailer to continue to blind nail pieces through the tongue edge.
Fit the last row and pull it tight with a pry bar. Face nail the course at the edge so the nails hide under the baseboard.
Hardwood Flooring Over Concrete
Cover the concrete slab with a 6 mil polyethylene plastic vapor barrier, overlapping the edges 4"-6" and extending enough poly to wrap up under the baseboards.
Lay 3/4" exterior-grade plywood sheets loosely over the floor area, leaving 3/4" gaps along the edges and 1/4" to 1/2" between the sheets. Stagger the joints every 4'.
At door openings and other edges where there is no finish trim, cut the plywood to fit within 1/8". Attach the plywood to the slab using a power-actuated concrete nailer.
Start at the center of the sheet and work out to the edges, making sure that the sheets are flat and securely fastened. Then cover the subfloor with 15 lb. builder's felt for additional vapor protection and underlayment.
Finally, a method that's gaining in popularity are treated sleepers that run perpendicularly below the flooring. First, install a loose layer of 6 mil polyethylene plastic for a vapor barrier.
Cut sleepers between 18" and 48" (longer lengths tend to warp). Lay them 12" apart on center, with the joints staggered, rather than butted.
Embed the sleepers in mastic, then secure them with cement nails. Add rigid insulation between the sleeper (optional) for extra protection.
Fasten an underlayment layer of plywood over the sleepers, then install the flooring.