How to Install French Doors

Before Getting Started

The location of the door, obstructions, the type of glass, and any screen options for exterior doors should be considered before starting a French door installation project. If the new doors will be installed in the same location as a set of old French doors or a sliding door, check the area around the doorway to ensure there will be enough space for the new doors to open and close.

Similarly, if you're installing French doors in a new doorway, it's a good idea to check for obstruction, as well as consider the best spot for comfortable access, sun exposure, and views. Clear glass panels give you a great view of the outdoors, but may not provide enough privacy. If this is the case, consider switching to textured or frosted panes.

When it comes to screen options, a standard sliding screen door isn't a good choice because the track may interfere with the function of the French doors. Instead, magnetic screen doors or a retractable screen door that rolls up into the door jamb may be the best option. You could also opt to leave the space open instead of installing a screen.

What You'll Need

Equipment / Tools

Pry bar
Screwdriver set
Drill
Tape measure
Hacksaw
Caulking gun
Level

Materials

French door kit with frame
Waterproof caulk
Door hardware
Door knobs
Nails
Screws

Instructions

How to Install French Doors

Measure the Doorway

Start this project by using a tape measure to take a measurement of the height and width of the current doorway. Make sure to remove the door trim with a pry bar before measuring the door to ensure that the measurement is as accurate as possible.

With this measurement, find and purchase a French door kit that will fit in the space. When considering potential products, keep in mind that there should be about 1/4 inch to 1/2 inch between the frame and the doors. If you can't find a kit that fits the doorway, you may need to order custom-made French doors.
Cut the Sill Pan

For exterior doors, you will need to measure the width of the door frame and cut the sill pan to the same size with a hacksaw. The sill pan helps to keep rain, sleet, and snow out of the home.
Apply Waterproof Caulk

Use a caulking gun and waterproof adhesive caulk to apply three rows of adhesive caulk along the base of the door frame. The adhesive caulk will keep the sill pan in place without screws and will help keep moisture out of the home.
Put the Sill Pan in Position

Slide the sill pan into position over the base of the door frame, then press it down onto the caulk, pushing evenly along the entire length of the sill pan to work out any air bubbles or uneven areas. You can also use a roller or a similarly shaped object to help flatten the sill pan.
Install the Door Frame

If you're installing exterior French doors, the door frame will have a base, but if you're installing an interior set of French doors, the frame will be three-sided.

For exterior doors, apply waterproof adhesive caulk along the perimeter of the sill pan, then seat the door frame into the sill pan. This will likely take more than one person to accomplish due to the width and weight of the door frame. Once the base of the door frame is in place, tilt the door frame up to slide it into position.

For interior French doors, simply tilt the door frame up and into position with the help of a partner. Slide the sides of the frame back against the bare edge of the doorway, ensuring that they sit as close to the doorway as possible.
Mount the French Doors

Some French door kits come with the doors pre-hung on the frames, while others come separately. If the doors are not hung on the frame, use the provided hinges and hardware to hang each door, ensuring that the base of the door is supported during installation to prevent the weight of the door from tearing out the screws. Use a level to double-check that the doors are installed correctly before proceeding.

Once the doors are hung on the frame, use a drill to drive a 3-inch screw through each hinge, securing the doors and door frame to either side of the doorway. Typically, the hinges will have a pre-drilled hole for this mounting screw.
Mark the Strike Plate Position

With the doors in place, close each door and mark where the shoot bolt hits at the top and bottom of the door. The shoot bolt locks the French doors in place but requires a strike plate for added security and durability.
Install the Strike Plates

Position each of the four strike plates according to the measurements taken in the previous step. Use a drill to secure each strike plate to the top and bottom of the door frame. Next, drill a hole through the center of the strike plate for the shoot bolt.

For interior French doors, decide if you want to install the bottom set of strike plates. Just keep in mind that the strike plate will need to be secured to the floor.
Seal the Door Frame

It's recommended to seal the door frame on the top and sides with waterproof caulk. Make sure to seal both the inside and the outside sections of the door to prevent moisture and air from seeping through the gaps.

Give the caulk about 24 hours to fully set, then reinstall the door trim or replace the door trim with a new decorative trim that better suits the French door aesthetic.
Install the Doorknobs and Lock

The final step of this project is to install the doorknobs and lock. If the French door kit did not come with this hardware, you will need to purchase suitable doorknobs and a lock for the installation. Follow the instructions provided by the manufacturer to position and secure the doorknobs and lock for each door.