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Learning Center - About Flooring Underlayment

Flooring underlayment is a layer of material used between the floor and subfloor or between carpet or a rug and the floor or subfloor. Underlayment servers as a padding which inhibits moisture transfer, insulates a room and absorbs sound. Underlayment also can absorb very minor imperfections or variations in the subfloor. There is a wide variety of underlayment ranging from basic to premium underlayment and each has its own benefits. Underlayment also includes carpet padding and moisture barriers. Underlayment is required for all floating floors, but also can be used to gain further sound deadening or insulation to a floor.

Foam Underlayment

A majority of underlayment is made from a type of foam. Many manufacturers make their own versions of underlayment, but they are essentially all the same. Foam underlayments are a base-grade underlayment consisting of a thin, foam padding which is typically around 1/8" thick. Foam underlayment will typically provide very little sound absorption, but suffice for the minimum necessary padding for a floating floor.

Modified Foam Underlayment

Some foam based underlayments, such as Sound 6 Barrier Acoustical Underlayment, are less porous and are far denser than typical foam underlayment, this results in a product which better supports the floor and reduces the amount of noise a floating floor produces drastically. Typically referred to as closed cell or high-density these underlayments are far superior to basic foam underlayment and are better suited for most residential and commercial installations, offer better stability to a floor, greater insulation and smoothes out minor subfloor imperfections.

Rubber Underlayment

Similar to modified foam underlayments when it comes to density and sound absorption, rubber underlayment tends to be a bit more moisture resistant and is usually a product of recycled rubber, giving rubber a more environmentally friendly profile. Rubber underlayment is typically similar in thickness to foam underlayment.

Cork Underlayment

Cork is one of the best underlayments available in the industry. The go to solution for most condominium associations, cork is a natural insulator and has a higher R-value that any other underlayment. Cork is also very dense, and supports a floor rather than cushioning; this causes a floating floor to feel more solid underfoot while absorbing sound transfer. Cork also comes from a natural renewable resource making it a popular "green" choice for the environmentally conscious. Cork is typically found in 3mm and 6mm thickness, with 6mm being a common standard in condominium requirements.

Unlike any other underlayment, cork can be used for more than just floating floors. Cork can be glued down, which makes it popular for increasing floor height or adding some sound absorption to a floor. For non-floating floors, cork underlayment must be glued down to the subfloor before installing flooring over it.

Carpet Padding

Unlike hardwood flooring underlayment, carpet padding is typically much softer. Most carpet padding or cushions are made from a variety of materials such as bonded urethane, jute, synthetic fiber, felt and rubber. Carpet padding is very important for carpet nowadays and like wood flooring underlayment it helps to make the carpet feel better under foot, while reducing sound transfer and insulating heat. It is important to note that carpet padding is not a suitable underlayment for wood flooring.

Combination Underlayment

Combination underlayment is typically a thin foam underlayment adhered to a moisture barrier and may or may not include built in seam tape. Although combination underlayment is a practical choice for quicker installations, these are base-grade choices and typically do not offer much cushioning or sound absorption.

Moisture Barrier

Moisture barriers are used in conjunction with underlayment when floating floors are installed over a concrete subfloor. Typically a 6mil polyethylene or Visqueen, moisture barriers are a thin plastic which prevents moisture vapor from coming up through concrete into the underlayment and flooring above. It is important to note that moisture barriers must be taped up at the seams to ensure proper sealing.