- NXT SKIM is a premium quality, fast-drying, cement-based underlayment designed for skim-coating, smoothing and leveling prior to the application of floor coverings. Apply from skim depth to 1" (0 - 25 mm). Install finished flooring as soon as 20 minutes after application. This trowel-applied product has a superior creamy consistency making it the ideal choice for skim coat applications.