A transom is a glazed or panelled section positioned above a door. Combining a transom with sidelights can increase daylight and visual height without making the door leaf itself unusually tall. The best configuration depends on the opening, architectural style, glass requirements, and installation details.
What is a transom?
A transom is the section above the door, often glazed. It can be rectangular or arched and may be combined with one or two sidelights.
Transom-only vs. transom plus sidelights
A transom adds height without increasing the door leaf height. Sidelights add width. Combining both creates a larger entrance assembly and should be sized as one coordinated system.
Glass and privacy
Clear glass maximizes daylight. Decorative or privacy glass changes visibility and appearance. For exterior applications, verify safety glazing requirements and the supplier’s glass specification.
Sizing considerations
Measure the existing opening or design the rough opening around the selected system. Do not assume a generic transom dimension will fit every door. Arched transoms require especially careful drawings.
Installation and specification
The door, frame, transom, sidelights, flashing, sill, and weather sealing need to work as a complete assembly. For custom projects, use manufacturer installation drawings.
FAQ
Can a transom be added to an existing door? Sometimes, but the opening and structural framing must be suitable.
Do transoms make doors taller? They increase the total entrance assembly height, not necessarily the door leaf height.
Can a transom be combined with sidelights? Yes, this is a common configuration.
Sourcing note
For project sourcing, specify the complete door assembly rather than the keyword alone: dimensions, material, finish, glazing, hardware, frame, threshold, and application. Jusen can quote custom aluminum and other door configurations where they match the project requirement.
Transom proportions
A transom should relate visually to the door below it. A narrow transom over a single door creates a different proportion from a wide transom over a double-door assembly.
Rectangular vs. arched
Rectangular transoms are generally simpler to specify. Arched transoms create a stronger architectural effect but require more precise drawings because the curved opening, frame and glazing must align.
Sidelights with a transom
When sidelights are added, the door, sidelights and transom become one coordinated opening. Confirm total width, total height, frame profile, glazing layout and structural requirements together.
Exterior safety and weather
Exterior assemblies need coordinated flashing, sill, threshold, weather seals and appropriate glazing. The transom should be treated as part of the exterior envelope.
Example specification
A project might specify a 36-inch entry door, one fixed sidelight, a rectangular glazed transom, a thermally improved frame and privacy glazing. The final rough opening should come from the selected unit drawing.
