Transom

A horizontal structural member or window located above a door, separated from the door panel by a transom bar. Transoms allow light and ventilation into interior spaces while maintaining privacy at eye level.

Fixed transoms contain stationary glass or panels, while operable transoms can open for ventilation-historically important before air conditioning, now used primarily for natural airflow strategies. Transom heights typically range from 12″ to 24″, though taller transoms are common in high-ceiling commercial spaces.

In fire-rated assemblies, transom frames must be integral with the door frame and glazed with fire-rated glass matching the door’s rating. The combined door and transom assembly requires testing and labeling as a unit. Transom lites can be rectangular, arched, or custom shapes. Related terms: sidelight, borrowed light, fanlight. Shop frames with transoms.