Exterior Door with Dog Door: Built-In Options

Cutting a hole in a perfectly good entry door makes most homeowners nervous — which is exactly why the factory-built exterior door with dog door exists. These are standard steel or fiberglass entry doors that ship with a pet door professionally integrated at the factory or fabrication shop: the opening is cut, framed, sealed, and warrantied as a unit, so you get the insulation, security, and weather performance of a real entry door without the DIY jigsaw gamble. This guide covers the options on the market, how to size the flap to your dog, the energy details that separate good pet doors from drafty ones, security realities, and what you’ll pay versus retrofitting.

How Built-In Pet Doors Are Sold

You’ll encounter three purchase paths:

• Factory/fabricator pre-cut doors. Companies and door shops sell prehung steel or fiberglass entry doors with a pet door installed — order the door style, the flap size, and the position, and it arrives ready to hang. Home Depot and Lowe’s both offer this through special order on select slabs, and regional door fabricators do it on nearly any slab you choose.
• Pet-door-ready patio and storm doors. Several manufacturers build sliding-glass and storm doors with integrated pet flaps — Larson storm doors with built-in pet doors are stocked items around $300-$500, and pet-panel sliding door inserts sidestep cutting entirely.
• Professional insert installation. A door shop or handyman installs a quality insert (PetSafe, Endura Flap, PlexiDor, Hale) into your existing slab. Not factory-built, but done with the right tooling and sealing it performs identically — this is the budget path.

Steel and fiberglass slabs both take pet doors well. Steel doors have a foam core between skins, so the cutout must be lined and sealed against moisture reaching the core; fiberglass slabs are more forgiving and don’t dent when a big dog hits the frame at speed. Solid wood doors accept pet doors most easily but bring wood’s maintenance baggage — the same trade-offs covered in our exterior door guide.

Sizing the Flap to the Dog

The rule: measure your dog’s width at the widest point (chest or hips) and height at the withers (top of shoulder). The flap should be at least 1 inch wider than the dog and the top of the flap 1 inch above the withers; the bottom sits 3-5 inches off the floor so the dog steps through rather than crawls. Standard industry sizes:

Two sizing mistakes dominate returns. First, buying for the puppy: size for the adult weight of the breed, since the door outlives the puppyhood by decades. Second, multi-pet households sizing to the average — size to the largest animal; the cat will happily use the Great Dane’s door. When between sizes, go up: dogs duck comfortably but won’t squeeze.

Energy Efficiency: Where Cheap Flaps Fail

A pet door is a hole in your thermal envelope, and flap quality determines whether it’s a managed hole or an open one. The hierarchy:

• Single vinyl flap: the $30-insert standard. Seals loosely, stiffens in cold, leaks air at the edges. Fine in San Diego, costly in Minneapolis.
• Double flap: two flaps with an air pocket between them — the pocket works like a storm window and roughly halves heat transfer. The minimum spec for four-season climates.
• Insulated dual-pane systems: Endura Flap’s polyolefin flaps with magnetic edge seals, PlexiDor’s hard acrylic saloon-style panels with weatherstripped closures, and Hale’s double-flap builds hold seal down to subzero and survive 10+ years of daily impact. These are the flaps factory door programs typically fit.

Look for magnetic perimeter sealing (not just a bottom magnet), replaceable flap assemblies, and a locking cover panel — an insulated slide-in panel that closes the opening for vacations and blizzards. Pair the flap upgrade with fresh exterior door weather stripping and the whole door assembly often ends up tighter than the original door was with its old sweep.

Security: Honest Talk

A pet door large enough for a German Shepherd is large enough for a person, and burglars know the reach-through trick — arm through the flap to the deadbolt thumb-turn. Mitigations that work:

• Position the pet door on the hinge side, low, maximizing distance to the deadbolt, or choose a double-cylinder deadbolt where code and fire-safety judgment allow.
• Locking cover panels in steel or heavy polycarbonate secure the opening at night; some insurers ask about them.
• Electronic flaps (SureFlap, PetSafe SmartDoor, High Tech Pet) unlock only for your pet’s collar tag or microchip — they stop other animals reliably and add a locking barrier, though the motorized panels are lighter-duty than passive flaps.
• Alarm sensors: a motion sensor covering the door’s interior approach costs $30 and removes the blind spot entirely.

Keep perspective: statistically, pet doors are a rare entry method — unlocked doors and windows dominate — but sizing XL flaps into a secluded rear door deserves the cover panel habit.

What It Costs

• Storm door with built-in pet door: $300-$550 installed on an existing entry.
• Pet panel for sliding glass door: $150-$400, tool-free, renter-friendly.
• Quality insert professionally installed in your existing slab: $150-$400 for the insert plus $100-$300 labor.
• New prehung steel/fiberglass entry door with factory pet door: $600-$1,400 for the unit depending on slab quality and flap brand, plus $250-$600 installation — total $850-$2,000.
• Premium fiberglass door with PlexiDor/Hale XL build-in: $1,500-$3,000 total.

The math favors the built-in when you needed a new door anyway — an aging, warped, or leaky entry slab plus a $400 insert job costs most of a new integrated unit that solves both problems and carries one warranty.

Placement and Installation Notes

Put the pet door in the door your dog already uses, on the leeward side of the house if you have the choice — wind-driven rain tests every flap. Garage-to-yard doors are popular hosts (note that house-to-garage fire doors must not be cut; keep pet doors out of rated fire doors entirely — another argument for the yard-facing wall or door). Threshold height matters for seniors: arthritic dogs want the flap bottom closer to 3 inches off the floor and a step or ramp outside if there’s a drop. Training runs days, not weeks: prop the flap open, treat through the opening, then lower it progressively. Most dogs are self-service within a week; the stubborn ones respond to a smearing of peanut butter at nose height, historically undefeated.

Flap Replacement: The Long-Game Question

Flaps are wear items — UV, cold cycles, and ten thousand nose-punches eventually stiffen or crack any material. Before committing to a door, confirm replacement flap availability and cost: Endura, PlexiDor, Hale, and PetSafe all sell replacement flap assemblies ($20-$120 depending on size and system), which means the door itself never needs touching again. No-name integrated pet doors without a parts channel turn a $40 flap failure into a whole-insert or whole-door problem in year eight. It’s the same logic as any long-lived fixture: buy the brand with a parts drawer.

FAQ

Can you buy an exterior door with a dog door already installed?

Yes — big-box special order programs, regional door fabricators, and storm-door lines like Larson all sell doors with factory-integrated pet doors, prehung and ready to install.

Does a dog door ruin an exterior door’s insulation?

A single cheap flap costs real energy; a double-flap or insulated system with magnetic seals reduces the penalty to a minor line item — typically far less loss than an aging door’s own perimeter leaks.

What size dog door does a Labrador need?

A large — roughly 10 x 16 inches of flap — suits most Labs (55-80 lb). Measure withers height and add an inch; a tall male may cross into XL territory.

Buy the flap quality first, the door style second, and size for the dog you’ll have in five years — that’s the whole formula for a pet entrance you never think about again.