- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 01 Apr 2021
Transoms are members that form horizontal divisions between units of a window, door, screen or glass curtain wall. Together with vertical members known as mullions they provide rigid support to glazing.
Transoms mechanisms can include:
- Bottom-hinged transoms with latches and chains that require a pole to pull the latch open.
- Side-hinged transoms that open like doors.
- Top-hinged transoms with fixed lifts that can be hand-operated.
- Automated opening mechanisms.
The purpose of a transom window can be to provide ventilation or additional light. Larger transoms windows are sometimes designed to provide the illusion of door height, without the need to produce extra-large door sizes especially, in higher ceiling areas. Transom windows can also be decorative and ornate.
Historically, transom windows were popular as an architectural feature, with stained-glass, decorative details or art deco styling. Modern transoms windows are commonly made from materials such as timber, aluminium, steel and UPVC.
Transom windows can be formed and installed in many different shapes. It is popular in Mediterranean style architecture to have fan-shaped transoms. Transoms can range from rectangular to circular and asymmetrical shapes.
 Related articles on Designing Buildings Wiki
Featured articles and news
Recognising past and present role models for the future.
So why not write something?
LETI publishes guidance for energy efficient home retrofits.
Predictions about adequate post-pandemic IAQ in non-domestic buildings.
Government publishes plans to 'build back greener'.
The contentious nature of claims associated with cladding, fire safety and EWS1 forms.
ECA comments on low-carbon heating systems initiative and Heat and Buildings Strategy.
Cinders and other forms of domestic rubbish created filth but also generated great wealth.
CIC 2050 Group requests input to find out priorities for future industry leaders.