French doors can provide a great feeling of light and openness to a room, and are an attractive alternative to basic patio and exterior doors.  Professional builders will be experienced at fitting doors to all kinds of different surfaces from drywall through plaster, but you will need to double check the instructions that come with the doors to ensure you understand any particular installation requirements.

Step 1 – Measure Up
As with most building projects the first job is measure up and ensure the parts you want to fit can be installed into the space available.  Start by measuring the jamb depth of the French doors (this should also be in the catalogue) and compare it to the combined thickness of both the interior wall finish and also the exterior wall sheathing.  You may find that you need a custom jamb for older homes, as standard French door packages will most likely be designed to fit the modern construction standards, and most manufacturers will be able to provide you with custom jambs to suit your needs (although this will cost more).

Step 2 – Wall Opening
If you do not already have a door space you will need to create a rough opening in the wall, so make sure you have all of the measurements for the new French doors such as the unit dimension height and width of the doors including the jambs. The rough opening should be about one inch wider and 5/8 inch higher than the unit dimensions, and this will give you some room to maneuver as you fit the door and make the adjustments you need to ensure it operates smoothly.  You will also be able to add insulation around the door if you leave more space in the opening and this can be much more energy efficient and will cut down on air infiltration and dampness around the new French doors.  If you are creating a new opening then you will need to check the structural plans of the property before you start in case there are any specific structural concerns that need to be addresses, and in most cases you will need to install a new structural header and you should use good dimensional lumber such as 2×10′s or 2×12′s.

Step 3 – Flashing Pan
It is important to remember to install flashing pans to any new exterior door openings, as these devices are essential for collecting any water than could run down the sides of the door and try and seep under the threshold, and will redirect water effectively away from the house in most weather conditions.

Step 4 – Fitting
Now you can fit the French doors following the instructions (or you may have done this enough times to fit from memory) and this should be a reasonably quick job now that all the preparatory work is out of the way.