How to Install French Doors

French doors — a pair of glass-paneled doors that open from the center — are one of the most elegant and light-enhancing upgrades you can make to a home. They connect indoor and outdoor spaces beautifully, flood rooms with natural light, and add significant architectural character. Here's how to install them.

What You'll Need

• Soft-close cabinet hinges (for door hinges): Soft Close Cabinet Door Hinges, 20-Pack
• Stud finder: Stud Finder Wall Scanner 5-in-1
• Laser level: Laser Level Line Tool by AikTryee
• Power drill: BLACK+DECKER 12V Drill & Home Tool Kit
• Screwdriver set: CRAFTSMAN Screwdriver Set, 8-Piece
• Miter saw: SKIL 10" Dual Bevel Sliding Compound Miter Saw
• Brad nailer: Metabo HPT Brad Nailer 18 Gauge NT50AE2
• Finish nails: Mr. Pen Nail Assortment Kit, 600 Pcs
• Construction adhesive: Loctite PL Premium Construction Adhesive
• Caulk gun kit: Professional Caulk Gun Kit 5-in-1
• Silicone caulk: GE Advanced Silicone Caulk, Clear
• Wood filler: BONCART Wood Filler White, Paintable
• Flexible molding trim: 32.8ft Flexible Peel and Stick Molding Trim, White
• Painter's tape: ScotchBlue Original Painter's Tape
• Sandpaper: Atosun 45PCS Sandpaper Set
• Vapor barrier: Crawl Space Vapor Barrier 10Mil Film

Types of French Door Installations

• Replacing an existing door: The most straightforward installation — the rough opening already exists.
• Replacing a window: Requires enlarging the opening to the floor, which involves structural work.
• New opening in a wall: Most complex — requires framing a new opening with a proper header.

Step 1: Prepare the Rough Opening

The rough opening should be 2 inches wider and 2 inches taller than the door unit (the pre-hung door frame). Use the stud finder to locate the king studs and jack studs on each side of the opening. Ensure the header above the opening is properly sized for the span — French doors are wide and require a substantial header. Check local building codes for header sizing requirements.

Step 2: Check the Opening

Use the laser level to check that the rough opening is plumb, level, and square. Measure the diagonals — they should be equal. An out-of-square opening will cause the doors to bind or not close properly. Shim as needed to correct any issues before installing the door unit.

Step 3: Apply Flashing and Vapor Barrier (Exterior Installations)

For exterior French doors, apply self-adhesive flashing tape around the rough opening before installing the door unit. This prevents water infiltration. Apply vapor barrier material as required by local code. This step is critical for exterior installations — water damage around door frames is one of the most common and costly home repair issues.

Step 4: Set the Door Unit in the Opening

French doors typically come as a pre-hung unit — both doors already hung in a frame. With a helper, lift the unit into the rough opening. Center it in the opening and check that it's plumb and level using the laser level. Insert shims between the door frame and the rough opening framing at the hinge locations and at the top corners to hold it in position.

Step 5: Secure the Frame

Drive screws through the door frame into the jack studs and header, through the shim locations. Use the provided long screws through the hinge locations for maximum strength. Check plumb and level after each screw — driving screws can pull the frame out of alignment. Open and close both doors to test operation before fully securing.

Step 6: Install Door Casing

Install door casing (trim) on both sides of the door using the miter saw and brad nailer. Miter the corners at 45 degrees. Use flexible peel-and-stick molding trim for a quick option. Nail the casing to both the door frame and the wall framing.

Step 7: Caulk, Fill, and Paint

For exterior doors, apply a generous bead of GE silicone caulk around the exterior perimeter where the casing meets the siding. Fill nail holes with BONCART wood filler. Paint the casing and door frame.

Step 8: Install Hardware

Install the door handles, deadbolt (for exterior doors), and any astragal (the vertical strip that seals the gap between the two doors when closed). Adjust the door hinges so both doors hang perfectly and close with even gaps all around.

Pro Tips

• Always check plumb, level, and square before securing — a misaligned frame is very difficult to correct after the fact.
• For exterior French doors, use a door unit with a low-E glass coating for energy efficiency.
• The astragal seal between the two doors is critical for weather resistance — ensure it's properly installed and adjusted.
• French doors that open outward are more weather-resistant; doors that open inward are more convenient for interior use.
• Consider adding a transom window above French doors for even more light and architectural impact.