When thinking of a floor most people will make an immediate connection to the visible layer such as the carpet, hardwood, tile, terrazzo, or a similar floor covering. Few consider the layers beneath the surface that comprise the floor system including the underlayment, subfloor, and joists. In this article we will highlight the components of a flooring system and explore the relationship of the floor covering to the rest of the floor system.

1) Finished Floor Coverings

The floor covering is the final part of the floor system that is visible. It is what we walk on and commonly refer to as the ‘floor’.

There are numerous types of floor coverings such as ceramic tile, hardwoods, carpet, laminate, cork, and many more.

The floor covering is traditionally chosen by the homeowner or architect, and heavily influences the type of underlayemnt that will be used.

2) Underlayment

While unseen once the floor covering is placed over top, the underlayment is the layer of the floor system that is just below the floor covering.

Although it isinvisible, underlayment is essential in many floor systems. The main purpose is to provide a flat surface for the floor covering to be placed on. Depending on the underlayment selected, it can also be used to soften the feeling of the flooring underfoot, reduce the sound of footsteps, and potentially act as a moisture barrier.

The material for underlayment varies in thickness and it can be made out of a variety of materials. Some of the most common materials are plywood, hardboard, cement board, hydraulic cements, or gypsum concrete. The underlayment material used for the flooring system is selected based on the floor covering.

3) Subfloor

Below the floor covering and underlayment is the subfloor. The subfloor is normally 19/32- to 1 1/8-inches thick and is made of OSB or plywood. The subfloor is responsible for the strength of the floor system and is attached to the floor joists.

4) Joists

Joists are lateral wooden framing members that rest on foundation walls and beams. They provide structural support for the framing system and when incorporated into a floor framing system, joists are used to provide stiffness to the subfloor sheathing.

There are two common types of floor joists: natural lumber and engineered lumber. While either material is commonly used, engineered lumber produces a more predictable floor system that is stronger and lighter than natural lumber.

When it comes to creating a floor system, selecting the floor covering may be the most important for visual satisfaction, however, selecting all of the other products such as the underlayment is equally as important. This is because the underlayment ultimately determines the acoustics of the floor and the feeling of the floor while walking. The subfloor material selected determines the strength of the floor system, and the joists will determine the predictability and longevity of the floor system.

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