Read our dedicated toughened-glass cat flap guide →
Why can’t the existing double-glazed unit just be cut?
Most glazed doors use safety glass, and toughened glass cannot normally be cut after the toughening process. A sealed double-glazed unit is also designed as a complete insulated unit, so drilling through an existing finished unit is not the correct installation method.
Instead, the glass is measured and a new unit is ordered to the correct size and specification with the pet-flap opening prepared in advance.
How is a cat flap fitted into double glazing?
The make and model must be confirmed because opening sizes and glass adaptors vary.
We check the sealed unit size, thickness, frame and required safety-glass specification.
A new made-to-measure unit is manufactured with the correct opening prepared for the chosen flap.
The original sealed unit is carefully taken out of the frame.
The replacement unit is glazed into the frame and the cat flap is installed and finished neatly.
Can you put a cat flap in toughened glass?
Yes, but not by cutting an already-toughened pane. The opening needs to be prepared before the new glass is toughened. This is why an accurate measurement and the exact cat-flap model are needed before the replacement glass is ordered.
What about patio doors and French doors?
Cat flaps can often be incorporated into glazed patio doors, French doors and full-height glazed back doors. The method depends on the frame, glass size, safety-glass requirements and the position of the opening. Large units can also affect handling and installation requirements.
Can a microchip cat flap be fitted into glass?
Many microchip cat flaps are designed for glass installation when used with the correct manufacturer-approved opening and any required mounting adaptor. The exact hole size varies by product, so do not order replacement glass until the final flap model has been chosen.
For example, Sure Petcare lists a 212mm optimum circular glass opening for its current Microchip Cat Flap, while larger pet-door models can require a different opening. Always use the dimensions for your exact model rather than a generic measurement.
Still choosing? See our comparison of microchip cat flaps for glass doors.
How much does a cat flap in double glazing cost?
Glass installations are quoted separately because the cost depends on the size and specification of the replacement unit, the type of safety glass, access, the flap model and whether the installation is in a standard door, French door or larger glazed panel.
Our general cat-flap installation service starts from £95 for suitable straightforward door or panel installations. Double-glazing jobs require a separate quotation because replacement glass has to be manufactured.
Should I keep the old glass?
If the original unit is undamaged and you have somewhere safe to store it, keeping it can be useful if you later want to restore the door to its original condition, for example when moving home or changing the pet-flap arrangement.
What should I send for a quote?
- A clear photo of the whole door or window
- A close-up of the glass and frame
- The cat-flap make and model, or a product link
- Your postcode
- Approximate glass dimensions if they can be taken safely
Need a cat flap fitted into double glazing in London?
M25 Glazing can measure the existing unit, arrange the correctly prepared replacement glass and fit your cat flap. See our full Cat Flap & Dog Flap Installation London service or send photos on WhatsApp for a quotation.
Frequently asked questions
Can you install a cat flap in double glazing?
Yes. A replacement double-glazed unit is normally manufactured with the correct opening and installed in place of the existing unit.
Can existing toughened glass be cut?
No. Toughened glass cannot normally be cut after toughening. A new pane with the opening prepared before toughening is usually required.
Do I need to buy the cat flap before the glass is ordered?
You should at least choose the exact make and model first, because the required opening size varies between products.
Can microchip cat flaps go in double glazing?
Many can, provided the correct glass opening and any required manufacturer adaptor are used.