Concrete overbeams (also called purlins or lintel) are generally beams erected over window and door openings to carry the upper masonry load of the window or door opening. A precast concrete transom is a transom that is prefabricated in a mould and then installed over the corresponding door or window or at the top of the doorway. There are also cast-in-place versions.

Precast concrete transoms are available in various sizes and lengths, from a minimum of 1m to a maximum of 12m, and can be customised.