Installation foam is an in-situ foam used for sealing in the building industry. It is then referred to as "foaming". Installation foam is normally based on polyurethane, hence the frequently used names PU foam and PUR foam. It adheres very well to many materials. It is available as a one-component foam (1K) or as a two-component variant (2K). The substrate must be clean, dry, free of dust, grease, wax and resin.