The subfloor provides the strength and the durability over time to a floor. Many floors are in fact a subfloor, and have no separate floor covering on top of the subfloor. The subfloor can also provide room for additional features of the floor, like underfloor heating ducts, or likewise, a system of ducts for air conditioning.
On a ground-level floor, the subfloor can be an earthen floor made of soil, though it must be sealed and protected so that moisture and insect infestation doesn’t touch the floor. Solid ground floors are usually made of a concrete slab.
Types of Subfloor
The subfloor can be made of different kinds of materials, usually wood. The plywood subfloor is the most common. It should be made of at least ¾ inch thick plywood which is laid across the floor joists and secured.
The plank subfloor is stronger and desirable when a stronger floor is needed. This kind of subfloor would be constructed with 4X8 inch by ¾ inch planks, and secured by nailing or using deck screws.