The most popular way to fasten a floor to a concrete slab would be to glue it directly to the slab using one of many different types of engineered flooring choices, but does pose some risk as they can make for a loud floor. This is where the benefit of a floating floor can work better.

They say nowadays you can glue solid hardwood directly to a slab, but I know for a fact most contractors would run from this type of installation. Most of this advice typically comes from inexperienced salespeople at those big box stores. Installing a solid wood floor over concrete can be done by either gluing and shooting concrete pins through 3/4 inch plywood then nailing to the plywood.

However, the best method would be to float a double layer of 5/8 inch plywood over the slab and then nail to it. Sounds odd doesn't it? It is fast becoming the norm with many professional hardwood guys as it does a better job at keeping potential moisture coming from the concrete that can cause problems.