Dog Flap Installation in the UK: Sizes, Doors, Costs & What to Expect

Cats get most of the attention, but dog flaps are one of the fastest-growing parts of our installation work. Whether you've got a Cockapoo who needs the garden at 6 a.m. or a Labrador who's bored of waiting at the door, a properly fitted dog flap changes daily life. Here's what every UK dog owner should know before booking an installer.

If any of these sound familiar, the answer is probably yes:

• You're up and down letting the dog out multiple times a day • Your dog scratches the back door or whines when you're working from home • You'd like to leave the dog at home for slightly longer without worrying about the garden • You've got a secure, enclosed garden and a sensible dog

A dog flap doesn't replace walks or supervision — but it removes the constant interruption of door duty.

Dog flap sizing is based on two measurements: your dog's shoulder width (so they fit through comfortably) and their chest height from the floor (so the flap is positioned at the right height).

As a rough guide:

• Small (up to 7 kg — Yorkies, Chihuahuas, small Terriers): a standard large cat flap or SureFlap Pet Door works well. • Medium (7–18 kg — Cockapoos, Spaniels, Beagles, French Bulldogs): PetSafe Staywell 740 or Pet-Tek Patio Pet Door medium. • Large (18–35 kg — Labradors, Golden Retrievers, Border Collies): PetSafe Staywell 660 large or Pet-Tek large. • Extra Large (35 kg+ — Rottweilers, German Shepherds, Great Danes): PetSafe Extreme Weather XL or specialist patio-panel inserts.

When in doubt, size up. A flap that's slightly too big is fine; a flap that's too small will be ignored.

We install dog flaps into:

• uPVC back doors (most common) • Composite doors • Wooden doors • Glass panels (via a replacement toughened unit — see our glass door guide) • French doors • Sliding patio doors (using a sash-panel insert that doesn't damage the door) • Conservatory side panels

The larger the flap, the more important the position. We always measure the dog before cutting.

Manual flaps are cheapest and simplest — 4-way locking gives you in-only, out-only, locked or unlocked. Fine if your dog is the only pet and you're not worried about strays.

Magnetic flaps use a collar magnet to unlock the flap. Good for keeping neighbouring cats out, less useful dog-to-dog.

Microchip flaps read your dog's vet microchip and only unlock for them. This is the gold standard if you have multiple pets, an open back garden, or live somewhere with foxes and other cats. The SureFlap Microchip Pet Door covers dogs up to medium size; larger breeds need a manual or magnetic flap.

If foxes are a worry, talk to us — there are specific timer-locking options that block flap use overnight.

Pricing scales with the door:

• uPVC, composite or wooden door: from £80 fitted, typically £90–£140 depending on flap size and brand. • Glass panel (replacement toughened unit): from £280, usually £320–£450 all-in. • Patio-door sash insert (no cutting, fully removable): from £180, depending on door height.

These prices include the flap itself when bought through us. We also fit customer-supplied flaps at a slightly lower labour rate.

Modern dog flaps are lockable in all four directions and most have a slide-in solid panel for when you're away. Insurance-wise, no UK insurer we've come across has ever flagged a fitted pet door as a problem — but as with cat flaps, the standard advice applies: don't leave keys in the inside of the door. (We've never had a customer report a problem after thousands of installations.)

For a standard door install:

• Arrival, dust sheets down, dog popped in another room. • We mark the aperture, double-check height with you, and cut. • Frames go in, seals applied, flap fitted, hardware tightened. • We talk you through 4-way locking and, for microchip flaps, register your dog. • Total time on site: 60–90 minutes.

For glass installs, see the two-visit process in our glass door guide.

Ready to scope out your dog flap? Send a photo of your back door and your dog's shoulder height through our quote form and we'll come back with a fixed price.