Things You'll Need
Astragal kit with wood screws
French doors can be a weak point for letting moisture, light, sounds, bugs, cold air and dirt into your home. It's not uncommon for a gap or crack to exist where the two doors come together. Because one or both of the French doors are moving, many traditional weatherstripping solutions just don't apply. An astragal is a formed strip that fits onto one or both doors where they meet, closing the gap. When properly installed, an astragal can replace poor sealing at the crack with a weathertight, soundproof and lightproof seal that will hold up under repeated use.
Identify which of the doors is active and which is the stationary door. If only one door will open regularly, that is the active door. Active doors generally have the doorknob lock while stationary doors have a floor-locking mechanism in place. If you cannot tell, choose the door that is used most as the active door.
Open and close the active door to see which way it swings. Stand on the side of the active door where you have to push the door away from you to open it. The astragal will be installed on the inactive door, and the molding piece will be on the side of the door you're standing on when the doors swing away from you.
Measure the height of the French door from the top of the threshold to just under the door frame. Record that measurement. Measure the space between the two doors and record that measurement. You'll also need to record the thickness of the door. Purchase an astragal that fits the specifications of the door from a door and window supply business that carries a variety of astragals. Many companies will do custom cuts for height.
Clean the surfaces of both doors with an all-purpose cleaner and a cleaning rag to eliminate any dirt and debris that might be stuck there.
Press the astragal strip onto the side of the door so that it wraps around. Begin at the top and press the astragal onto the door, working your way down to the bottom.
Locate the screw holes in the astragal strip. Using a drill, create pilot holes. Screw the astragal to the door until the heads of the screws are flush with the door surface. If the astragal kit came with channel covers, snap them in place over the screws.
While you can install an astragal onto a door while it is in place, you might find it easier to take the door off, install the astragal, then rehang the door. Always have a helper when removing and rehanging a door.