Can You Put a Cat Flap in a Glass Door? (UK Guide 2026)

Yes, you can put a cat flap in a glass door. It's one of the most common installations we carry out across the UK. What you *can't* do is cut a hole in the existing pane — toughened glass shatters into thousands of pieces the moment it's cut, drilled or scored.

The correct method, used by every reputable installer in the country, is to replace the affected pane with a brand-new toughened glass panel that has the cat flap aperture already cut into it before toughening. The new panel slots into your existing door frame and looks identical to the original — just with a tidy cat flap in it.

All modern UK glass doors (patio, French, bi-fold, conservatory, fully glazed back doors) use toughened safety glass. It's heat-treated under enormous stress so that if it breaks, it breaks into harmless granules rather than dangerous shards.

The downside: that internal stress means any attempt to cut, drill, score or even chip the edge causes the entire pane to disintegrate instantly. There is no workaround. If anyone offers to cut your existing glass for a cat flap, walk away — they're either uninformed or about to destroy your door.

The process is straightforward:

1. Measurement visit. We measure the existing glass unit precisely — width, height, thickness and whether it's single, double or triple glazed.
2. New panel manufactured. A like-for-like replacement is built with the cat flap hole pre-cut, then toughened. On double-glazed units the hole goes through both panes and the internal spacer bar is routed around it so the sealed unit stays airtight.
3. Fitting day. We remove your old pane, fit the new one into the existing frame, and install your chosen cat flap with a weatherproof seal. Total on-site time is 1–2 hours.

The finished result is a glass door that looks and behaves exactly as before, with a perfectly fitted cat flap.

Every common UK glass door:

• Patio doors (sliding and hinged)
• French doors
• Bi-fold doors — we usually fit into a fixed panel so the folding mechanism is untouched
• Conservatory doors
• Glass side panels next to a front or back door
• Fully glazed UPvc or composite back doors

It also works for single, double *and* triple glazing. The principle is the same — the affected pane is replaced as a whole unit.

From £280 for a standard installation, including the new toughened glass panel, the cat flap itself and full fitting. Price varies with panel size, whether the unit is double or triple glazed, and the cat flap model (basic manual vs microchip vs smart connected).

For comparison, a UPvc door cat flap fitting starts from £60 because the door panel is cut directly — no new glass required.

Two key timescales:

• Manufacture of the new toughened panel: 5–10 working days from when measurements are confirmed.
• On-site fitting: 1–2 hours once the new panel is ready.

So total turnaround is usually 1–2 weeks from quote to finished installation. If you're booking ahead of moving day or a holiday, mention it — we can usually plan around tight deadlines.

The new toughened panel is the same thickness and strength as your original, so security is unchanged. Microchip cat flaps (SureFlap, PetSafe, Closer Pets) seal shut automatically when your cat isn't nearby, so the opening is physically locked by default.

Most UK home insurers are completely relaxed about professionally fitted cat flaps. If yours has specific clauses, it's worth a quick check — but it's almost never an issue.

If you'd like a quote for a cat flap in a glass door, send us a photo of the door and we'll come back within 24 hours. We cover the North West, Cheshire, Staffordshire, Yorkshire and North Wales — see our cat flap in glass door service page for full details.