Our plastic lumber is manufactured with a slight wood grain-like texture, creating an easy to clean surface that is no more slippery when wet than a painted or sealed wood deck.A natural film, which can’t be seen or felt, is left on the surface of the material after manufacturing. Sunlight will normally “burn off” this film in a few weeks. A rougher, slip resistant (knurled) finish is available if required and lead time may be a factor.. Keep in mind that the coarser the surface finish, the more likely dirt will tend to collect on it.