French Door Dog Door Installation: A Complete Guide

How to Install a Dog Door in a French Door

Complete Guide to French Door Pet Door Installation
Three installation methods for adding a pet door to French doors: in-glass replacement, replace entire french door, and glass panel replacement. All 3 options are reversible if you were to move in the future (unless you replace multiple panes of glass due to dog's size)

⏱️ Estimated Time: 1–4 Hours (depending on method)  |  🔧 Difficulty: Moderate to Advanced  |  👤 People Needed: 1–2

How to Install a Dog Door in a French Door – Complete Guide

Before You Begin

French doors are among the most popular, and sometimes the most challenging, locations for pet door installation. Their multi-pane glass design, narrow stile widths, and decorative character all require careful planning. The good news: there are three distinct installation methods for French doors, and one of them will work for your situation.

🔀 Three French Door Pet Door Installation Methods

Option 1: In-Glass Replacement

Replace one glass pane with a new tempered glass panel that has the pet door built in. Preserves the French door look. Requires custom glass fabrication.

Best for: Homeowners who want the cleanest appearance.

Difficulty: Advanced (professional recommended)

Option 2: Custom Glass Pane with Dog Door

Replace one glass pane with a custom-built pane specifically designed to house a pet door. The new pane matches the original profile but includes an integrated pet door flap.

Best for: Homeowners wanting a factory-integrated look.

Difficulty: Moderate to Advanced (professional recommended)

Option 3: Full Door Panel Replacement

Replace the entire French door panel with a new door that has a pet door pre-installed. The most comprehensive solution.

Best for: Older French doors due for replacement.

Difficulty: Moderate

📋 Things to Consider Before Installation

  • Active vs. Inactive Door: French doors have two panels – one is the "active" door you use daily, the other is typically bolted shut or "Dead/Dummy (inactive) Door. Install the pet door in the inactive panel whenever possible so your primary door operates normally.
  • Glass Configuration: True divided-light French doors have small individual glass panes separated by real partition or muntins (wood dividers). Simulated divided-light doors have one large glass pane with decorative grilles on the surface. Simulated-light doors are much easier to work with for in-glass installations.
  • Pane Size: If your French door has true divided lights, the individual panes may be too small for a pet door. In this case, Option 3 (through-panel cut or full replacement) may be your best choice.
  • Door Material: French doors come in wood, fiberglass, steel, and aluminum-clad wood. The material affects which installation methods are feasible.
  • Aesthetics: French doors are architectural features. Consider how each installation method will affect the door's appearance from both inside and outside.
  • Weatherproofing: French doors often have larger gaps between the two door panels. Ensure your pet door installation doesn't compromise the existing weatherstripping.
  • Door Swing: French doors can swing inward or outward. The hinge placement and swing direction matters when replacing the entire french door with a new custom made stainless steel or fiberglass door.

Tools & Materials You'll Need

Tools depend on your chosen method. Below covers all three options.

🔧 Tools

📦 Materials

Option 1: In-Glass Replacement Method

This method replaces one glass pane in the French door with a new tempered glass panel that has the notch made in the bottom corner or center for the pet door integration.

Step 1: Identify the Target Pane

  • Choose the lowest full-size glass pane in the inactive French door panel.
  • For simulated divided-light doors (one large glass with decorative grilles): the grilles pop off or unscrew, exposing the full glass panel. You'll replace the entire glass sheet.
  • For true divided-light doors: you'll need a pane large enough to fit the pet door. If no single pane is large enough to fit you pet, consider Option 2 or 3, or remove multiple panes of glass.

Step 2: Measure & Order Custom Glass

  1. Measure the glass pane precisely (overall width, height, thickness and style) to 1/16″.
  2. Order a custom tempered glass panel with the pet door opening pre-cut and then tempered. Specify glass dimensions, type (single/dual-pane, Low-E, etc.), and pet door size/position.
  3. Allow 2–3 weeks for custom fabrication.

Step 3: Remove the Old Glass

  1. Remove decorative grilles if present (for simulated divided-light doors).
  2. Remove interior trim stops or glazing compound around the target pane.
  3. Carefully remove the glass pane with suction cup lifters. Have a helper support the glass.
  4. Clean the frame channel of all old glazing, caulk, and debris.

Step 4: Install the New Glass + Pet Door

  1. Place setting blocks in the frame channel.
  2. Set the new glass panel into the frame with suction cup lifters.
  3. Secure with glazing points and apply glazing compound or reinstall trim stops.
  4. Mount the pet door frame halves onto the glass (interior and exterior sides).
  5. Reinstall decorative grilles around the new glass if applicable.
  6. Caulk all exterior edges and install the flap and security panel.

Option 2: Custom Glass Pane with Integrated Dog Door

This method replaces one glass pane with a factory-built unit that includes the pet door as an integral component of the pane.

Step 1: Measure the Existing Pane

  • Measure the target pane dimensions precisely, including the overall depth (how deep the glass sits in the frame plus the trim around where the pet door will be installed).
  • Photograph the door from both sides for reference when ordering.

Step 2: Order the Custom Pet Door

  • Contact Portal Pros to order a Custom Maxseal Pet Door sized for your French door.
  • The pet door unit arrives custom made to fit your exact dimensions 

Step 3: Swap the pane with the pet door

  1. Remove the single or multiple existing glass panes carefully
  2. Insert the new pet door unit into the frame.
  3. Secure with screws and create a seal with caulk around the exterior of the frame.
  4. The pet door is already installed in the pane – no additional frame mounting needed.
  5. Test the unit to ensure it operates as intendedl.

Option 3: Full Door Panel Replacement

This method replaces the entire inactive or active French door panel with a new door that has a rough cut already made for the pet door installation.

Step 1: Measure the Door Opening

  1. Measure the door panel: width, height, and thickness.
  2. Note the hinge type, placement, and count (measure from the top of the door down).
  3. Note the bolt/latch mechanism at top and bottom and measure to the center of the locking mechanisms from the top of the door down.
  4. Photograph the door from both sides.

Step 2: Order or Build the Replacement Door

  • Order a pre-hung French door panel with existing rough cut for the pet door integration from Portal Pros. Portal Pros offers one-lite, one-lite with partitions or one-lite with interna mini blinds.
  • Alternatively, purchase a matching French door panel and install a door-mount pet door into it (see our Door-Mount Installation Guide).
  • Match the door style, material, finish, and hardware to the existing active panel.

Step 3: Remove the Old Panel & Install the New One

  1. Remove the hinge pins or unscrew the hinges from the old inactive panel.
  2. Lift the old panel out of the frame.
  3. Transfer the hinges, bolts, and latch hardware to the new panel (if not pre-installed).
  4. Hang the new panel in the frame and reinstall hinge pins.
  5. Test the door swing, bolt engagement, and pet door flap operation.
  6. Apply weatherstripping between the two door panels if needed.

💡 Tips & Tricks

  • Always use the inactive panel if possible: Installing the pet door in the inactive (bolted) French door panel preserves the active door's full function and weather seal.
  • Photo-match grille patterns: When reinstalling decorative grilles on simulated divided-light doors, photograph the original layout first. Grille patterns can be tricky to reassemble correctly.
  • Consider the door's aesthetic from outside: In-glass installations look seamless from inside but verify the pet door frame doesn't clash with the door's exterior appearance.
  • Preserve the old panel: If you replace the entire door panel, store the original. You can reinstall it if you sell the home or no longer need the pet door.
  • Match the finish: French doors are prominent visual features. Take extra care to color-match paint, stain, or caulk for a professional result.
  • Check door swing clearance: Verify the pet door flap doesn't hit anything when the French door swings open.
  • Weather-test before finishing: After installation, wait for a rainstorm (or spray with a garden hose) to check for leaks before applying final paint or finish.

⚠️ Common Mistakes to Avoid

  • Cutting true divided-light muntins without a plan: Removing muntins from a true divided-light door changes its structural integrity and appearance. Plan carefully.
  • Ignoring the glass type: Replacing tempered glass with non-tempered glass in a door violates building codes and creates a safety hazard.
  • Rushing the glazing: Poorly applied glazing compound around the new glass lets water in and heat out. Take your time and apply clean, consistent beads.
  • Forgetting bottom bolt clearance: Many French doors have floor bolts on the inactive panel. Ensure the pet door doesn't interfere with bolt operation. Poral Pros installers will reintegrate the astragal with the new French Door Pet Door.

When to Call a Professional

French door installations combine the complexity of glass work with the precision of fine woodwork. Call a professional if:

  • Your French doors have true divided lights with small individual panes
  • The doors are historic, antique, or architecturally significant
  • You need custom glass fabrication and aren't sure about specifications
  • The inactive panel has complex multi-point locking hardware
  • You want a guaranteed watertight, draft-free installation
  • HOA rules require professional installation documentation
  • You do not feel comfortable measuring precisely.

Portal Pros specializes in French door pet door installations nationwide.
📞 Call 855-DOG-DOOR for a free estimate.

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