Installation of French doors may seem more complicated because of the double door jamb, however there is not much difference from installing a standard door. French doors are a very bold decorative statement and can give a real feeling of open space in a single room or between two rooms. French doors have a jamb on each side but no jamb in the middle. This makes them somewhat less apt for security than other doors when used on the outside of the home but newer lock technology and dead bolts make these a very feasible outside door choice.
1. Take Care in Measuring the Opening
When measuring the opening between door jambs you must be certain to measure carefully and take a few things into consideration. First you will need a 1/4 inch gap between the first door jamb and the first door. Next you will account for the length of one door. In between the doors themselves there will be another 1/4 inch gap and no jamb. Then account for the length of the second door. There will be one more 1/4 inch gap between the second door and the second door jamb and then 1 inch for each door jamb. For your jambs to be installed and your doors to swing and work properly all of these measurements must be precise.
2. Interior vs Exterior French Door Jambs
When installing exterior French door jambs you will take into consideration the same things that you do when installing interior French door jambs. On exterior French doors, the top portion of the frame between the two door jambs will often be larger and heavier than on interior French doors. With exterior French doors, sealing and weather proofing the door frame to include the door jambs is a much bigger concern. Make certain to weather proof the frame itself and the area surrounding it and then install the doors and seal them as well.
3. Plumbing the Jambs
The key element in making sure that any door has clearance and swings properly is in plumbing the door jambs. Making sure that the door jambs are plumb can be a little challenging giving the distance that they are apart but it is extremely important to make sure this is done accurately. Start by placing the butt of the vertical 2-by-4 on the base marking and then line it up with the marking on the top of the door frame. Use a 4-foot level and place it along the side of the 2-by-4. Once you have fine tuned the leveling of the vertical 2-by-4 hold it in place with some nails placed at an angle next to the board to keep it from moving. Now use a tape measure to measure the distance between the jambs at the top of the door and at the bottom of the door. If these measurements match exactly then it is safe to finish your framing and mount your doors.