According to architectural practices, “transom” is a term that is given to any transverse horizontal structural bar or beam. It is also used to describe a crosspiece that separates a door from the window located above it.

Transom windows, also known as transom lights or fanlights, are smaller-sized windows that are usually hinged and set above a doorframe or on a particularly high area of a wall. They have been used in architectural constructions for a very long time. The first were used to decorate early Gothic churches. These windows were unglazed windows located directly in the belfry. They also took the form of spire lights, where they were thought to be necessary to strengthen the overall church wall construction.

Toward the end of the Gothic period in architecture, it became common to include these types of windows in the during (6)-resized-600designs of all structures, including residences and businesses. They were very popular in building construction before the advent of central air because buildings with these windows stayed cooler and more comfortable in the hot summer months than buildings without them.

Today, these window types are highly prized in a variety of architectural settings for the enhanced cross-ventilation they provide while at the same time maintaining an individual’s security and privacy. There are many different types of transom windows that are available on the market today. Here are descriptions of just a few.

Paneled Glass

This type of transom window is built with a frame that is paneled to create a symmetrical pattern or design similar to a grid. These windows are elegant, simple pieces that can be affixed by hinging either at the base or the top of the frame, or on both frame sides. The glass panels that make up this type of transom are almost always divided by vertical strips of metal or wood, but sometimes larger paneled glass transoms include horizontal pieces of wood.

Solid Window

In contrast to the multi-paneled transom, some transoms feature just one piece of glass inside a solid, sturdy frame. Like the paneled transoms style, these solid windows can be affixed or hinged at the frame’s top, bottom or both sides. These solid transoms often feature a heavy piece of frosted, brightly colored or intricately etched glass. They might also contain a piece of glass that is highly embellished for enhanced beauty.

Fanned Window

These transoms are arched, fan-shaped or semicircular and are often called “fanlights” because they resembleFanTransomWindows open decorative fans. This type of window is either fixed in place or hinged at the base to allow the frame to swing from one direction to the other. This style of transom window is usually designed as much for decorative beauty as it is for practicality.

Major Brand Names

Most transom windows that are sold in the Northeast are constructed with vinyl and are manufactured by Pella. There are transoms available in other brand names, but Pella windows are some of the best.

Transoms can add beauty and functionality to any home or office building. To learn more about transom window styles and to see which one might be best for specific architectural needs, individuals should contact the professionals at United Home Experts.


Transom windows can be installed by themselves (as interior windows), or as decorations above doors and cased openings.  Standard carpentry tools such as nails and hammers are needed, as well as a few simple components to frame the transom.

In addition to the cased opening components, it is necessary to have adequate material for the fabrication of a jamb frame, a stop molding (for holding the sash in place), and a mullion (for installing the transom above your door).

Any homeowner who is looking to add both beauty and functionality to his or her home should consider installing transom windows. Most people won’t have any idea of where to start, so here are the basic instructions for completing transom window installation above a door.

Those that are really looking to take on this project themselves should first get a detailed set of instructions from the window manufacturers. This set of instructions is strictly to get an idea of the process. We are not responsible for any accidents, warranty voids or mishandling. We highly recommend allowing professionals, like ourselves, to replacing your windows. We offer the best warranties and coverage, aside from manufacturers, for replacement windows that are available to homeowners in the New England area.

Step 1. The first thing that is needed is a calculation of the final opening width. Based on this measurement, a transom jamb frame will need to be measured to fit that same width (about a quarter inch bigger on all side than the actual dimension of the door slab). This frame will be made using flat jamb material. The transom sash might need to be cut down slightly in order to fit inside the frame of the jamb.

Step 2. The transom sash should be centered inside the jamb frame and fastened to it. It is often easier to do this while lying on a flat surface to inhibit twisting during assembly. Temporary spacer blocks should be used to hold the transom sash in place until the stop molding can be applied. It is recommended that spacing nails or screws be fastened every eight to twelve inches.

Step 3. The stop molding needs to be cut and assembled on both sides of the sash to provide a completed look forduring (6)-resized-600 your transom. This has the added advantage of covering any gaps that might exist between the jamb frame and the sash.  Some common trim profiles that are used for this purpose include cove mold, quarter round, and square stop. Install shorter (vertical) stop pieces first.  This will allow for the bending of longer pieces into place to obtain a tight fit.

Step 4. The transom unit (the assembled sash and frame) should now be fastened on top of the cased opening or door.  To accomplish this, nail the transom jamb to the head jamb of the door (or cased opening) beneath it.

Step 5. Once everything is assembled, it will be necessary to measure the door and transom together as one unit.  Cut the casing (the two legs and the one header) and install on one complete side of the transom.  Then case the other side of the assembled door / transom after installing the door in the rough opening.  If the transom and the door are assembled directly at the foot of the opening, it is much easier to secure the door in its final position.

Step 6. After applying the casing, complete the transom trimming process by installing the mullion between the jamb frame and the door head jamb.  Adjust the mull detail by installing spacer blocks between the jambs and using a wide mullion to cover the gap.

Step 7. Next, the assembled unit (cased on one side) will need to be placed into the rough opening by plumbing and tacking.  Then shim and nail behind the jamb on the open, uncased, side.

Step 8. After shimming, the uncased side should be measured, cut, and completed.

Step 9. Repeat Step 6 for the unfinished side of the transom.

The process for installing a transom over a cased opening or by itself is completed in the exact same way (without the doors).

These are the basic steps one would take to install a window. Of course, after reading these instructions, some homeowners may prefer toleave the task to the professionals. United Home Experts can help; the company specializes in window installation and a variety of other home improvement projects for those living in the Eastern New England area.