If moisture conditions are acceptable, and the concrete tests for less than 3 Lbs Moisture per 1000 square ft Via Calcium chloride test ,or hardwood manufacturer specs , The most widely used applications are floating engineered flooring types. Floating floors are available in the click together or lock and fold style that require no gluing. More traditional 3/4″ solid hardwoods on concrete can be accomplished with the addition of a plywood subfloor, used as a nailing base over the concrete. However, this raises problems with door entries and other items. Overall vertical height of the new floor will increase by. I prefer to install locking, Floating engineered on Concrete , And to steer clear of any below grade application here in the rainy northwest. Concrete floors can test within spec at certain time then if a gutter downspout Breaks and directs water under the concrete floor you could have a problem.