Fit a cat flap in a uPVC door panel

Cut a hole in a uPVC door panel and fit a cat flap, checking first for hidden reinforcement and fire door rules.

CF-01Check the door and plan the jobConfirm this is a standard uPVC entrance or back door panel, not a glazed section or a fire door. Check if the door is under warranty, as cutting it usually voids that. Buy a cat flap sized for uPVC panels (not a timber-only kit) and read its fitting instructions before you start.

RULES

1 each · Cat flap kit (uPVC-rated, with tunnel)

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KNOW THE RULES

If this is a communal or flat entrance fire door, it will have a fire rating under Building Regulations Approved Document B. Cutting it without a certified fire-rated cat flap can break that rating. Fit only a fire-door-rated flap on these doors, or get advice first.

CF-02Measure and mark the flap positionMeasure your cat's belly height off the ground and mark the flap centre roughly 150-200mm up from the bottom of the door. Keep clear of the door edge, hinges, lock, and any glass. Use the manufacturer's template and a spirit level to mark a level, square outline.

1 each · Spirit level

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1 roll · Masking tape

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1 each · Pencil

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CF-03Check for hidden reinforcement before you cutMost uPVC door panels have a steel box-section running through the stiles, and sometimes across a mid-rail, for strength. Drill a small 3mm pilot hole at each corner of your marked outline first. Fine plastic dust means you're clear; metal swarf means you've hit the reinforcement and need to shift the flap position.

1 each · Drill bit, 3mm

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CF-04Cut the holeDrill a 6-8mm starter hole at each corner of the marked outline so the jigsaw blade can turn. Fit a fine-tooth blade suited to plastic and cut steadily along the line, supporting the panel from behind so it doesn't flex or crack. Wear safety goggles and a dust mask, as uPVC cutting throws up fine plastic dust and small shards.

1 each · Jigsaw blade, fine-tooth for plastic

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1 each · Safety goggles

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1 each · Dust mask

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CF-05Deburr the edges and test-fit the tunnelFile the cut edges smooth, removing sharp burrs and plastic strands. Push the flap's tunnel through the hole dry, without sealant, to check it sits flush and the flap swings freely without catching on the frame.

1 each · Flat file

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CF-06Fit the cat flapRun a thin bead of silicone sealant around the cut edge to stop water getting into the panel's foam core. Insert the tunnel from outside, fit the inner frame from inside, and screw the two halves together evenly using the screws supplied. Don't overtighten, as uPVC can crack under too much pressure.

1 tube · Silicone sealant, exterior grade

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1 each · Screwdriver

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CF-07Weatherproof and test the flapRun a neat bead of silicone around the outer edge where the frame meets the door, and smooth it with a wet finger. Leave it to cure for the time stated on the tube before use. Test the flap opens and closes freely, set the locking slider to your chosen mode, and check for draughts with your hand around the frame.

1 each · Cloth or rag

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CF-08Tidy upVacuum up plastic dust and any metal swarf from the doorstep, door surface and surrounding floor. Bag up the cut-out uPVC offcut for disposal. Give the door and flap a final wipe down and check all screws are still tight.

1 each · Vacuum cleaner or dustpan and brush

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