Floor & Subfloor Thickness

Typical Subfloor

• Most subfloors are built out of CDX tongue-and-groove plywood, although OSB (oriented strand board) has also been used in some cases. As a general rule, these subfloors are a minimum of 5/8-inch thick and range up to 3/4 inch in thickness. If a builder is worried about the bottom line, he tends to use the minimum thickness, but if the builder is worried about longevity and building a house to last, he’ll work with at least the 3/4-inch thickness. When building your own home, consider the fact that while you can save money on thinner material, it’s not as durable.

Above and Beyond

• While carpet, hardwood and laminate materials are installed directly on top of a normal subfloor, ceramic tile and natural stone installations have extra requirements. For basic ceramic tile, you need to add at least a 1/4-inch-thick layer of backerboard on top of the subfloor, which adds to the overall height of the floor -- 1/2 inch is preferred. In the case of natural stone such as flagstone or granite and marble, the subfloor has to be even thicker, with two layers of 3/4-inch exterior-grade plywood required to build up the floor to withstand the weight of the stone.

Concrete Subfloors

• Most concrete slabs are at least 4 to 6 inches thick and are poured on top of the ground so they don’t add to the overall height of the floor. However, in certain rooms of a house, such as entryways, tile or natural stone is desired; rather than use a backerboard, the builder often prefers to float a “mud" or concrete layer that is 2 to 4 inches thick to provide a base for the tile. Since this is too thick to match the rest of the finish floor, a special drop-down section of flooring is built into the frame of the home, with its own joist system that ties into the rest of the home. From here, two layers of 3/4-inch-thick plywood form the base for the concrete subfloor.

Traditional Flooring Material

• Tile is generally 1/4 to 3/8 inch in thickness; natural stones are generally thicker, and you have to add at least 1/8 inch for the thickness of the concrete mortar beneath the tile after compression. Carpet ranges from 1/4 to 1/2 inch in general thickness. Laminate materials range from linoleum tile, which is around 1/8-inch thick, up to the look-alike wood planks that are 1/2 inch or so in thickness. Good hardwood will be around 3/4-inch thick, but varies depending on the type of wood you are working with.