Wood Floor installations and whether you nail down, glue down or float a floor depends on the subfloor surface and the type of material that is being installed. Concrete slabs are not suitable for nailing down a floor unless a plywood subfloor is installed over the slab. If the elevation of the floor is not designed into the construction of the home to accommodate the additional subfloor then adding the plywood will affect the height of the floor, door transitions and elevation differences to other flooring materials, etc. Directly over slab installations including glueing down directly over the slab or floating the floor. Floating floors require a underlayment and either click and lock or glue tongue and groove joints will be the mechanical joining of the floor. Advantages to a floating floor are ease of installation and the unrestricted seasonal movement of the floor from expansion and contraction. Laminate floors and engineered floors are approved for this type of installation. Disadvantage for some will be the sound that a floating floor will make especially with high heels and hard soled shoes giving off a hollow sound in the floor. One option to dampen the hollow sound is to use a high quality 3-in-1 or 5-in1 underlayment such as “Quiet Walk” underlayment that is considerably thicker than the standard foam or 6 mil plastic underlayment sheeting. Glue down installation over slabs have the advantage of a solid sound and feel. Considerations include whether you are glueing down over radiant floors and if so then a Engineered product is generally more stable than a solid wood floor. Glue reduces but does not eliminate wood movement. Most adhesives have a memory characteristic which also makes any removal in the future a labor intensive process. Glue is its own vapor barrier but must be cleaned up properly. Disadvantage to glue down installation is that the process will take longer then nail or floating installations and any future removal of the floor is labor intensive. Nail down installations are the traditional method of installation. The advantage to nail down installation is that you have the solid sound and feel of a permanent installation that also allows for practical repairs in the future if needed.