Transom
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.
The smaller window above a door or window can also be known as a transom window. A transom window can be fixed or operational.
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.
In door frames with transom windows, the transom can provide similar structural properties as a lintel. It can provide strength and support to both the door and window frame.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Ebenezer Howard: inventor of the garden city. Book review.
The Grenfell Tower fire, eight years on
A time to pause and reflect as Dubai tower block fire reported just before anniversary.
Airtightness Topic Guide BSRIA TG 27/2025
Explaining the basics of airtightness, what it is, why it's important, when it's required and how it's carried out.
Construction contract awards hit lowest point of 2025
Plummeting for second consecutive month, intensifying concerns for housing and infrastructure goals.
Understanding Mental Health in the Built Environment 2025
Examining the state of mental health in construction, shedding light on levels of stress, anxiety and depression.
The benefits of engaging with insulation manufacturers
When considering ground floor constructions.
Lighting Industry endorses Blueprint for Electrification
The Lighting Industry Association fully supports the ECA Blueprint as a timely, urgent call to action.
BSRIA Sentinel Clerk of Works Training Case Study
Strengthening expertise to enhance service delivery with integrated cutting-edge industry knowledge.
Impact report from the Supply Chain Sustainability School
Free sustainability skills, training and support delivered to thousands of UK companies to help cut carbon.
The Building Safety Forum at the Installershow 2025
With speakers confirmed for 24 June as part of Building Safety Week.
The UK’s largest air pollution campaign.
Future Homes Standard, now includes solar, but what else?
Will the new standard, due to in the Autumn, go far enough in terms of performance ?
BSRIA Briefing: Cleaner Air, Better tomorrow
A look back at issues relating to inside and outside air quality, discussed during the BSRIA briefing in 2023.
Restoring Abbotsford's hothouse
Bringing the writer Walter Scott's garden to life.
Reflections on the spending review with CIAT.
Retired firefighter cycles world to raise Grenfell funds
Leaving on 14 June 2025 Stephen will raise money for youth and schools through the Grenfell Foundation.
Key points for construction at a glance with industry reactions.