The underlayment is the thin, flexible sheet of resilient material that is installed on top of a subfloor in order to act as a base for the laminate sheets or tiles that are being installed. While the subfloor provides the foundational support for the room, the underlayment is the foundation for the floor and is intended to enhance and protect the flooring itself. It has the following functions: it slightly levels the flooring; it cushions the laminate planks; it reduces sound transmission.
Proper selection and installation of underlayment is important because it can determine how your laminate flooring wears over time. The type of underlayment chosen should be based on the environment that it is being installed in, the type of floor that has been purchased, and your own personal needs for space.
Concrete subfloors: When installing over a concrete subfloor, the main concern is moisture considerations. Concrete is a porous material that can allow water to seep up into it and through to your flooring. This can cause adhesives to loosen, tiles to warp, and mold and mildew to develop. With a concrete subfloor, you need an underlayment that acts as a vapor barrier, in order to prevent moisture from penetrating through to your laminate installation.
Plywood subfloors: In many cases, you will not want to use a vapor barrier-type underlayment when installing on a standard plywood subfloor, as wood is a natural material that needs to breathe. Installing a vapor barrier over this can cause moisture to become trapped within the material leading to the growth of mold or warping in the material. The exception is when laminate flooring is being installed in a high moisture area, such as a bathroom or basement.
Noise reduction: Some types of underlayment can act as a barrier against the transmission of noise. This can be important in certain working environments where silence is necessary, or in bedrooms where peace and quiet is preferred.
Types of Laminate Underlayment
It is important to note that the use of carpet padding or other soft flooring underlayments will not increase the comfort of people walking on hard flooring installations.
Standard foam underlayment: This consists of a thin strip of foam material that acts as a cushion between the subfloor and the laminate flooring. This is the most common form of laminate underlayment, and it is often used in cases where laminate flooring is being installed over a plywood subfloor.
Combination foam underlayment: This type of underlayment combines standard foam with a vapor barrier layer that will protect the installation from rising moisture. Slightly more expensive than standard foam, this underlayment is appropriate for both plywood and concrete subfloors and can be used in most environments.
Cork underlayment: This material is used in flooring installations where noise reduction is important. While it does not provide any more cushioning or comfort underneath a laminate installation, it can be used to level uneven surfaces between rooms. It also has natural anti-microbial characteristics.