Transom windows seem to have a bit of mystery about them. A lot of people don’t understand exactly what a transom window is so I figured that it was high time that this window guy wrote a post explaining the ins and outs of transom windows.
A transom window is essentially another window above a window or door. This bonus window is typically installed as a part of the primary door or window trim and casing though it is technically its own jamb and sash. Transom windows get their name from the horizontal bar that separates the window from the door or window below it. This bar is called a transom and so the window above was called a transom window.
While transom windows are commonly found on exterior windows and doors they are common above interior doors as well. Transom windows serve several purposes depending on the style of the building.
Before the days of central heat and air it was imperative to get good airflow between rooms of the house to keep occupants warm or cool. At night when bedroom doors were closed for privacy, an operable transom window above each door could be opened to provide the airflow but maintain privacy.
This was especially helpful is large hotels and row houses where only the outside rooms would have windows, leaving the interior rooms stifling in the summer.
Especially before electric light transom windows were crucial to spreading the sunlight to interior rooms. Similar to a laylight the transom could provide light into the building’s dim interior. After electricity became commonplace transoms still provide light keeping electric bills lower than they otherwise would be.
Commonly you’ll find solid wood entry doors with a transom window above it to light the foyer.
Transom windows are styled differently on different architectural styles. Victorian style homes often have more ornate designs with the transom’s muntins compared to Craftsman style homes which have a simpler design. Tudor style transom windows often have leaded glass inserts with diamond shaped panes of glass.
Can You Add a Transom Window?
Anything is possible, but adding a transom window is not as easy as just cutting a hole above your existing window or door. Adding a transom window where one didn’t previously exist can be a real challenge because it will require modifying the header.
The header is a structural framing member above a window or door that transfers the load of the house around the opening down to the rest of the framing. Removing that header can cause sagging or structural damage to the wall causing potentially dangerous conditions.
To add a transom window you will have to remove the plaster or drywall above the existing window/door and then build temporary supports for the wall while you remove the header and install a new header at the taller height to accommodate the new transom window.
Can it be done? Yes. Does it require a lot of extra work and expense? Yes.
Are Transom Windows Operable?
That depends. Some transom windows are operable and other were fixed in place for light and decoration only. Just because your transom doesn’t operate doesn’t mean it was originally operable. It may have just been caulked shut and lost its hardware over the years.
Look for hints like hinges or screw holes from old hardware. Any signs of these will mean you had an operable transom window at some point and it likely can be made to operate again. Transoms operate typically in just a couple ways.
Hopper transoms operate with hinges on the bottom allowing the top of the window to tilt inward or outward depending on the design. These typically have a latch at the top of the sash to hold it closed and chain that will stop the transom from flopping all the way open. The chain typically allows the transom to open about 3-5 inches allowing plenty of airflow.
An awning style transom operates the opposite from an awning style. The hinges are on the top allowing the bottom of the window to swing up a few inches typically toward the outside, but there are in-swing varieties though they are much rarer.
Restoring a Transom Window
The restoration of an original transom window is very similar to the restoration of any other historic window like a casement or double-hung window. The process involves cutting the sash free of the excess paint or caulk so you can remove it. Then removing any hardware to strip the paint and lubricate it to get thing moving smoothly again if you have an operable transom window.
I’ve outlined the whole window restoration practice in this resource page if you feel ready to tackle the restoration of your transom window check it out here.
We talked about the latch, chain, and hinges common on transom windows, but there are other hardware options to help opening this kind of window since they are usually beyond the reach of the average height person.
Transom operators mount directly on the sash and allow you open or close the window without climbing on a ladder. There are also transom pole hangers that attach to the window and a latch hook that you attach to the end of a wood pole that can be used to open and close transoms on very tall windows. House of Antique Hardware is a great source for a variety of transom window hardware.
Hopefully, this post has helped you understand transom windows a little bit more. They are a unique piece of architecture and like with almost all historic architecture they performed a function. Let’s enjoy that function of light and airflow with this unique type of window.
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I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.