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Flooring layer

Definition of Underlayment

The underlayment is a material about ¼ or ½-inch thick that sits right under the floor covering. 

Various materials, such as plywood, fiber felt, rubber, hardboard, thin foam padding, or cement board, can be used as underlayment.

The right underlayment material is determined by the choice of floor covering material. Flooring underlayment has various uses, including:

  • Providing cushioning
  • Sound absorption and insulation
  • Reducing the wear and tear of flooring
  • Acting as a “vapor barrier” to prevent moisture from damaging your floors

Example of Underlayment in a Sentence

“The underlayment sits right below the subfloor and creates an even and smooth surface for the floor covering.”


  • Underlay

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