Window Mullions and Transoms – A Glossary

What Are Window Mullions and Transoms? Here at Thames Valley Windows, we make sure to keep homeowners informed about all the architectural window jargon. You may not have heard of window mullions and transoms before; however, you have likely seen them! Ultimately, they are the specific names for the beams on modern windows. Let’s take a closer look.

What Are Window Mullions?

Window mullions are vertical beams that form divisions between units of a window, door or glass curtain wall. They can support the glass involved or structural support to a window arch or lintel. They generally pair up with transoms. But what do transoms do?

What Are Window Transoms?

Window transoms divide window glazing into different sections. Unlike mullions, these beams are horizontal. Therefore, mullions and transoms work together to provide support for windows in all shapes and sizes.

Do All Windows Use Mullions and Transoms?

In most cases, you will find that mullions and transoms are used for decorative purposes to the modern window framing system. They are useful because they prevent you from having to install one pane of glass for a window by dividing into smaller window openings. Many double glazed window solutions are split up into sections, or lights, either for aesthetics or to support any building regulations which might apply.

How Are Mullions and Transoms Used?

The use of stone mullions in architecture dates back prior to the 10th century. Modern mullions and transoms offer synthetic support in many double glazed window materials from uPVC, Timber, Timber Effect and Aluminum. This not just for visual support or regulation, either, as they can help the user to access their windows more easily.

Mullions and transoms ensure that glazing is fully supported from the use of angles, inserts, support metal and drilled anchors connecting the mullion system to the structure of the building. This means that for example, in the case of blowy or stormy weather, panes of glass receive full protection by transferring the force to the actual building, making sure that windows are safe and secure.

Find Out More

All new modern double glazed windows are designed with mullions and transoms, so If you are looking for new or replacements windows for your home in Berkshire, Surrey, Oxfordshire or beyond, contact one of our expert window designer for your free, no-obligation quotation