Please note this is a flat roof kerb only, no window is included. Flat roof kerb All of the benefits of a VELUX roof window in a flat roof. Structural opening of 60cm x 115cm required. Insulated timber kerb to allow the installation of standard VELUX roof windows in a flat roof. Select the insulated timber kerb to match the size of your roof window. Glazing with a laminated inner pane is recommended for high level applications. Roofing material is dressed up the sides of the kerb, then overlapped with the aluminium cover parts. Properties 10 year guarantee on flat roof kerbs. Suitable for roof pitches between 0 and 15°.