Underlayment

Underlayment may refer to:


 * Underlay, a material placed underneath floor carpet, other flooring materials, or mattress bedding
 * Underlayment, a water-resistant or waterproof layer used beneath many types of commercially available roofing material
 * Bituminous waterproofing, systems designed to protect residential and commercial buildings
 * SDM strength film, a kind of High Density Polyethylene (HDPE) Cross Laminated Strength Film
 * Tar paper, a heavy-duty paper used in construction
 * Underlayment in road construction such as nonwoven fabric
 * Underlay, a material in sewing
 * Underlay, a technique in some types of surgery such as myringoplasty
 * Underlay, a material in printing