How to fit a cat flap
Quick answer: Choose a cat flap that suits your cat, mark the cut-out using the template (about 15 cm above the bottom of a wooden door), drill corner holes, cut the opening with a jigsaw, sand and seal the edges, then fit the frame and tunnel. Do not cut into glass, fire doors or doors you do not own.
A cat flap takes a bit of care but it is a satisfying job. It is easiest in a solid wooden door. Doors made of uPVC, composite or glass are a different matter and are best done by the supplier or a fitter.
Think about the cat first. A kitten grows, a large cat needs a big flap, and microchip flaps only let your cat in.
What you will need
- A cat flap with template and fixing screws
- Pencil, tape measure and spirit level
- Drill with wood bit
- A jigsaw with a fine wood blade
- Sandpaper
- Paint or varnish to seal the bare wood
- Masking tape, and a screwdriver
Step by step
Pick the right type
Choose a flap that is big enough for your cat to walk through. Measure the cat's height at the shoulder and its width. A microchip or magnetic flap stops other cats from entering.
Check the door
The door must be solid wood. Do not cut a fire door (marked FD30 or similar), a glass panel, or a door you rent without permission. Check what is inside the door: some have glass inserts or a hollow core.
Choose the position
The bottom of the opening should be about 10 to 15 cm above the floor so the cat can step through. Keep it clear of the lock, hinges and the bottom rail of the door.
Mark the template
Tape the template to the door, check it is level with the spirit level, and mark the corners of the cutting line on the door. Repeat on the other side.
Drill the corners and cut
Drill a hole inside each corner of the cutting line. Put masking tape over the saw line to reduce splintering. Cut from hole to hole with a jigsaw, keeping the blade straight.
Sand and seal
Sand the cut edges smooth and seal the bare wood with paint or varnish, so it does not take in water and swell.
Fit the flap
Fit the frame on each side. Screw the two halves together through the door, using the supplied screws, and fit the tunnel if there is one. Check the flap swings freely and shuts.
Tips
- Introduce the cat gradually: prop the flap open at first and use treats.
- A tunnel extension helps on thick doors.
- Lock the flap at night if you want to keep the cat in.
Stop and get help if
- The door is glass, uPVC, composite or a fire door.
- You rent the property and have not asked the landlord.
- You are not confident using a jigsaw and cutting a clean hole. A badly cut hole ruins the door.
- The flap would be next to a lock or letterbox and weaken the door's security.
Would you rather we did it?
We cover Sandwich and East Kent. Send us a quick message on WhatsApp, ideally with a photo, and we will come back with a price and a day.
Common questions
Can I fit a cat flap in a uPVC door?
Not easily. uPVC and composite doors are built with a frame and sealed panels, and cutting them can affect the warranty and security. Many suppliers offer a cat flap fitting service.
How high should a cat flap be?
The bottom edge should be about 10 to 15 cm above the floor. A cat should step through without jumping.
Will a cat flap make my house less secure?
A well-fitted flap on a lockable setting is generally fine, and a small flap does not let an adult in. Do not put it where someone could reach the lock.
More guides
Last reviewed 17 October 2026. This guide is general information for UK homes and is not a substitute for the manufacturer's instructions. If the job involves gas, mains wiring, asbestos, structural work or working at height, or you are unsure, ask a suitably qualified person.