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French Door Styling: Frames, Transoms & Sidelights

As gorgeous as a good set of internal French doors can be, many buyers tend to only focus on the doors themselves, neglecting to explore the other accutrements that can be added to your doors to further improve their aesthetic value. This is especially true with interior French doors, as you'll need to spend more time actually looking at them, so you're going to want to make sure you're happy with how they look. Here we'll take you through all the major options available to help you decide which, if any, you might want to use with your own French doors. And remember, you don't need to choose just one either!

French Door Framing

Whilst you don't necessarily need a transom or a sidelight installed, every set of French doors needs to be framed. It's more than likely, of course, that a frame will already be installed in the opening you wish to install your French doors, but even if that is the case, you might want to consider replacing it, as you'll be able to tailor the frame to suit your specific tastes. You will also use the frame as a base from which to install all other accessories, so take that into account before you start the installation. Either way, installing a frame can be a tricky process, so you might want to hire a professional. If you are confident in your DIY abilities, however, here we'll take you through the process of framing your interior French doors.

  • First, you'll need to prepare your tools, so make sure you have a level and set square, a saw, nails and the wood you'll be using as the frame or the framing kit.

  • Next, measure the opening, and make sure you are thorough! You really don't want to be making any mistakes here. Remember, you'll be hanging at least two doors, so you'll need to double all calculations, and there are also three gaps and the door jamb to consider. You'll also need to allow room for a vertical side plate and a gap of around a quarter of an inch between both the doors and the jamb on both sides. Measure the width, then the height from the floor up and add an inch for the bottom jamb and 2 for the top jamb.

  • Now you'll need to construct the frame itself, which is a task that will differ drastically depending on the size of your opening. The best way is to start with a simple square 2x4 frame and mark your measurements on it. Next, remove all the 2x4 boards that are between your markings, then pull the board until it comes away from the top nails and remove any remaining nails. Now, cut the portion of the bottom plate out that is within the width of the frame and you should be off to a good start.

  • Now it's time to install the header. Measure from the floor to the top plate and mark the board, cutting another 2x4 to needed length. Nail it to the underneath side at the end of the bottom plate and mark a spot on the top plate where the 2x4 is level and then nail it in place, repeating the process on the other side. Join two 2x6's together with a piece of 1/4 inch plywood sandwiched between the two and install the header to the top of the 2x4's where the top of the frame will be.

  • To finish the frame, add another 2x4 next to the other vertical slats to form a double post on the outside of the header then angle some nails into the top and bottom plate as well as into the other vertical post. Measure the distance between the header and the bottom of the top plate and, following the measurements you have taken, nail the 2x4 slats in place.

  • Of course, if this all sounds incredibly confusing to you then you might want to consider hiring a professional for this part. Or at very least watching a few YouTube tutorials! Remember you might also want to leave room in your frame for any of the accessories listed below to make life easier for yourself later on, so remember to take them into account when making your measurements! Again, this is not an easy job so don't feel like a failure if you need to ask for help!

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What Are French Door Transoms?

Now that you have your frame installed we can start looking at the exciting stuff! Transoms are windows installed above your French doors, and can bring not only more light into the room, but can offer a really unique look that will really help your French doors stand out. Transoms are available in a variety of different shapes and sizes and can be altered to fit bespoke openings if need be. They also look wonderful when combined with sidelights, especially if you're going for a more ornate look. Why would you want to install a transom window above your interior French doors? Because they look great by adding a little bit of height to your doors, are surprisingly easy to install (at least compared to installing a frame from scratch), and can really lend your home a certain kind of period charm, as well as a great deal of extra light and warmth from a functional perspective.

Installing A Transom Window

Note that this refers to the method involved when installing a transom window above a French door set that's already been installed. If you're framing a French door from scratch, you'll want to take the transom into account during the framing process. Nine times out of ten you'll be installing the transom at the same time as the doors themselves, of course.

  • First, measure out the space in which you'll be installing your transom, as you'll then need to measure a jamb frame to fit that space. If there is no space above your French doors, actually removing the part of the wall in which you'll be installing the transom itself is obviously not a job we recommend doing yourself unless you really know what you're doing and are happy with the structural integrity of your home.

  • Cut your transom frame using your measurements, making sure to add an extra quarter inch to all measurements before you start cutting.

  • Place the frame into the opening using shims to hold it in place for the time being.

  • Nail in the frame using spacing nails around every 9 to 12 inches, making sure the frame is secured to the top of the French door frame and to the top and sides at the wall.

  • Next, you'll want to experiment, adding shims where necessary and screwing the frame down until you're 100% confident it's secure. It's no exact science, but you'll get there eventually.

  • Once the frame is installed, you'll need to install the casing or moulding, then you can simply slot in your window. You'll want to make sure the connection between this trim, the jamb and the walls is tight. You'll also want to ensure that the trim around the transom matches any existing trims around the frame. Or you might want to redo the entire thing.

What are French Door Sidelights?

A sidelight is a common fixture that you'll find adorning many French doors, perhaps more so than transom windows, especially in older houses where the ceilings are quite low. Sidelights are extra windows that will flank your door. These can often be seen in many front doors and patio doors but can work just as well inside the house flanking internal French doors. In much the same manner as transom windows, they bring extra light into a room and can really help fill out an opening that's maybe not quite big enough to fit in an extra pair of doors. When combined with a transom window, the results are generally very impressive, but they can work just as well on their lonesome. As far as installing new sidelights? Nine times out of ten the space for them will already be built into the frame, as adding them in later would require taking down the existing frame and widening the opening, which is definitely a job for a professional. If you really want to add sidelights, however, you can use the same basic steps above, only you'll be working on the sides, not above.


We understand that this is not the easiest of subjects to discuss without actually showing you the processes involved in installing frames, transoms and sidelights, but these are certainly not beginners jobs. Hopefully, however, we've at least been able to give you an insight into what options are available to you.

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If you have a question which isn't covered by one of our handy guides, why not drop us an email and we'll be happy to assist.

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