Fibrecloth, slip or sealing layers are different types of separation layers in a roof structure that intend to protect roof coverings, structures or other sealing layers.

A migration barrier is used to lay between two layers to prevent chemical influence between them. A sliding layer is laid between two layers to prevent excessive friction between them. A levelling layer is laid between two layers to hide unevenness in the substrate. A protective layer is normally laid over the membrane to protect it from mechanical stress and the like. Fire protection layers are laid between two layers to prevent burning objects from melting into combustible insulation material.