How to Install a Pet Door in an Exterior Door

Pet doors are one of the most-requested handyman jobs in family neighborhoods. Solid prep keeps the door weatherproof for years.

Pet door height is measured to your pet's chest. The opening top should be 1" above the tallest pet's shoulders, and the step-over (bottom of opening to floor) should be lower than the elbow. Mark the cutout on both sides of the door using the manufacturer's template.

Drill 1/2" starter holes at each corner of the template. Use a jigsaw to cut between the holes — go slow, support the cutout piece as you finish so it doesn't break out splinters. For metal-skinned insulated doors (most modern exteriors), expect to cut through fiberglass insulation and a second metal skin on the inside — a fresh jigsaw blade matters.

Most pet door frames clamp through the cut hole with screws connecting the inside and outside frames. Apply a bead of silicone around the frame before installing to seal against air and water. Tighten the frame screws evenly to avoid warping the plastic.

Test the flap from both sides and confirm your pet can use it before you celebrate. Some dogs need encouragement; some refuse for weeks. Magnetic-flap doors weather-seal better than basic vinyl flaps — worth the extra $30.