Introduction
Considering fitting a cat flap in double glazing? If you are weighing up the best way for your cat to come and go without leaving doors ajar, a cat flap in glass is often the neatest solution. The challenge is knowing what is possible with modern double and triple glazing, patio doors and conservatories, and how to get it done properly without compromising your home.
This guide explains the professional process from survey to installation, what to expect on timings, which doors and frames are suitable, and how we ensure a weather-tight, secure and tidy finish. It also answers the most common questions homeowners ask about fitting a cat flap in a glass unit or conservatory.
The short answer
Yes, you can have a cat flap in a double-glazed or triple-glazed unit, in most patio, French and bifold doors, and in conservatory glazing. The key is to replace the existing pane with a new sealed unit that is manufactured with a precision cut-out and toughened safety glass. Glass cannot be cut after toughening, so accurate measuring and templating upfront is essential.
How professional cat flap in double glazing works
Modern insulated glass units are factory-sealed systems. To preserve their performance, you do not alter the existing pane. Instead, a new unit is made to size with a circular cut-out for your chosen cat flap model. For doors and low-level glazing, the replacement is typically toughened safety glass to meet Building Regulations and maintain safety.
Here is what that means in practice:
- Measurement and templating. A trained glazier surveys the opening and frame type, confirms glass specification, and captures exact sizes. If you already own a cat flap, we note the required hole size from the manufacturer’s template. For microchip flaps and slimline designs the tolerances are tight, so precision is crucial.
- Fabrication. Your new sealed unit is made to order with the cut-out and any required features, such as Low-E coatings, argon fill and warm-edge spacers. The glass is then toughened where needed. Because cutting happens before toughening, no on-site drilling is involved.
- Installation. Once ready, we remove the old pane, fit the new unit, install and seal the cat flap, then test operation and weathering. Where requested, we can safely remove your original glass for a future refit* (*additional charges may apply).
All cat flap sealed units supplied and fitted by Aaran Glass carry a 5-year guarantee against misting, so you can be confident your new pane will stay clear. Lead times vary with specification and toughening plant schedules, but we keep you informed from order to fitting.
Suitable door and window types
Most common setups can accommodate a professionally manufactured unit with a cut-out:
- Double and triple glazing in uPVC, aluminium and timber frames
- Patio sliders, French doors and bifold doors
- Conservatory side panes and some conservatory doors
- Single glazing and low-level side lights
For sliding patio doors that pass over one another, a slimline cat flap model prevents clash clearance issues. Your survey will confirm the best placement and flap type.
If you are considering a window cat flap, placing the cut-out in a lower side light often keeps access comfortable for your cat while preserving sightlines. We also work with leaded and Georgian-bar units; the new unit is made to match the look.
For more detail on options and sizing, see our overview of cat flaps for glass, including microchipped models and slimline units for sliders at the Aaran Glass cat flap page.
Microchipped and app-connected cat flaps
Microchip-enabled flaps, such as SureFlap models, are well suited to glass installations. They help stop neighbourhood cats from wandering in and can include curfew modes and, on some versions, app connectivity. During the survey we check the exact hole size and backplate requirements so the cut-out is manufactured to the correct tolerance and the finish sits flush and neat.
If you are choosing a new model and want guidance on sizes or features for a cat flap for a glass door or window, our buying advice covers typical dimensions and compatibility.
Weather-sealing, security and finish
A well-fitted cat flap unit does not mean draughts or a messy bead of silicone. The replacement sealed unit is built to today’s insulating standards, and the flap is installed with appropriate gaskets and sealants so it sits flat, closes cleanly and resists the weather.
Security remains a priority. Toughened safety glass is stronger than standard float glass, and quality cat flaps include lockable modes. Placement is chosen to avoid weakening mullions or transoms, and frames are re-beaded correctly so you keep the original door or window performance. Customers routinely remark on the tidy finish and how seamlessly the flap blends with existing glazing.
Measurement, templating and lead times
Because safety glass cannot be altered once toughened, the first visit is all about accuracy:
- Initially an idea of price can be given over the phone/ email based on rough measurements or photo of your window or door pane.
- We would then arrange a site survey and take exact sizes to the millimetre, confirm glass spec and spacer colour, and note any coatings or argon fill you would like to retain.
- Depending on the cat flap you are opting for, we work from the manufacturer data showing the cut out required to suit the cat flap in hand.
- A written quote follows. On approval and deposit, we place the unit into production.
- Typical lead times are discussed at survey and depend on glass type, toughening schedules and logistics, on average from point of measurement it is around 2 weeks. We will propose fitting dates as soon as the unit clears quality checks.
Fitting day, access and frame types
On installation day, we protect floors, remove the old pane, clean down the frame, and fit the new unit using the correct packers and seals for your frame material, whether uPVC, aluminium or timber. We then mount the cat flap, seal neatly and test the action several times. Finally, we clear away packaging and, if agreed, put aside the old pane for safe storage* or this is safely and environmentally disposed of at our premises.
If your project involves other glazing tasks or you need help elsewhere in the property, our team also handles misted unit replacement, hinges and handles replacements and related repairs. Learn more about causes and cures for double glazing mist on our guide to why units mist on the inside.
Conservatories and garden rooms
Yes, you can put a cat flap in a conservatory. The same principles apply: we replace a panel with a new unit that includes the cut-out and uses toughened safety glass where required. We will suggest the best pane to use so your cat has a natural route to the garden, and so operation stays smooth year-round as the structure expands and contracts with temperature.
FAQs
Can you put a cat flap in a double-glazed unit?
- Yes. The existing panel is replaced with a new sealed unit that is made with a precision cut-out and toughened glass. You cannot cut into the current pane on site.
Can you put a cat door into double glazing?
Yes. The process is the same as above and suits microchip flaps as well as standard models. Measurement accuracy is vital because glass cannot be cut after toughening.
Can you put a cat flap in a conservatory?
Yes. We typically choose a lower side panel or door pane, manufacture a matching unit with the cut-out, and fit the flap with proper seals for a tidy, weather-tight result.
What does it cost?
Pricing depends on size, glass specification, access and your chosen cat flap. We provide free estimates, and final written quotes follow a site survey. Bespoke units require a deposit before manufacture. If you are comparing options, we are happy to break down what is included and advise on the most cost-effective route.
Summary and next steps
A cat flap in a glass door, window or conservatory is straightforward when handled by professional glaziers. The pane is replaced with a purpose-made sealed unit that carries a 5-year warranty against misting up, the flap is sealed neatly, and your home’s security and insulation are protected. Choose a microchipped or slimline model if needed, and rely on precise measurement to get the perfect fit.
Serving London and the South East, Aaran Glass can survey, manufacture and install your new unit with minimal disruption. To explore models and installation options, browse our cat flap guidance and examples at our cat flap service page, or talk to our team for a free estimate.
