How to Install French Doors in 11 Steps

Before getting started, carefully measure the existing door opening (minus any existing trim), as well as the surrounding area, to ensure that the French doors will fit in the opening and can fully open and close without obstruction. The door manufacturer will indicate the necessary rough opening size, so consult the instructions for the best fit. 

If your rough opening is a non-standard size, you may need to know how to reframe the door, so it’s best to be aware of that before you start installing French doors.

For safety’s sake, enlist help for positioning and holding the doors, as the doors are heavy and the glass can break easily. Ensure you’re wearing appropriate safety protection as well; work gloves and safety glasses will protect you as you complete this project.

Begin by using a pry bar and rubber mallet to gently remove any existing trim around the door opening, including any floor trim. Set the trim aside if you plan to reinstall it once your new doors have been installed. Once the trim has been removed, you’ll be left with the rough opening. Re-measure the opening to confirm that your new doors will fit properly.

If you’re installing French doors as exterior doors, you’ll need to install a sill pan at the bottom of the frame to keep water from coming into the house and causing damage. Measure and cut the sill pan to the width of the door frame. Install the sill pan by applying several rows of waterproof caulk along the base of the door frame, then press the pan into place until it is firmly affixed.

Using your level and carpenter’s square, make sure the rough opening is level and square before installing the door frame. If the opening is not level or square, you’ll need to use shims when installing the door frame to ensure the doors are hung correctly.

If your new doors come already hung on the frame, remove the doors to make installing the frame more manageable. Have a helping hand lift the frame into the opening. Using your level and shims, shim the frame so that it sits level and square in the opening. Use your drill to make pilot holes through the frame and the shims, and drive the nails in to roughly secure the frame. You may need to make final adjustments before you fully secure the frame.

With a partner’s help to support the doors, hang them on the frame. Use a drill and the hardware that came with the French doors to mount the door to the frame. Before fully securing the frame, test the doors to ensure they’re hung square and level, they can open and close properly, and all gaps around the doors are of equal size.

Once you confirm that the doors are hung properly, install the door hinges and secure the frame by drilling 3-inch screws through the hinge screw holes, securing them to the frame and the door opening. Finish nailing the frame into place, making sure that all shims are secure as well. Caulk around the door frame, and wait 24 hours for it to dry before reinstalling the trim.

After the caulk dries, you can reinstall the door trim using the disassembled parts you set aside or install new trim to match the style of your French doors.

French doors have top and bottom locks that each require a strike plate that secures the latch of the lock. Use a measuring tape or simply mark where each bolt touches the sides of the doors to determine where you’ll install the strike plates. Drill each plate in place with the hardware provided.

If the doorknobs and locks did not come pre-installed on your doors, you’ll need to install them. Installing the door knobs and locks varies from door kit to door kit, so follow the instruction manual to ensure you install them correctly.