Cat Flaps & Dog Doors in Double Glazed Glass — Everything You Need to Know
One of the most common questions we receive at Pet-Tek is: "Can I fit a cat flap, or a dog door, in my double glazed glass?" The short answer is yes for both, but there are important things to understand before you book a glazier. This guide covers exactly how it works, what to watch out for, and which Pet-Tek Catwalk® cat door and Dogwalk® dog door models are best suited for double glazing installations. For a full overview of all glass fitting options, see our glass fitting cat door range or our cat flap advice guide.
- ✓ Yes: Pet-Tek glass fitting cat doors suit glass from 3mm to 28mm and Dogwalk® dual glaze dog doors suit glass up to 32mm, covering the vast majority of standard double glazed units.
- ✗ Not a DIY job: cutting through double glazed glass requires a qualified glazier with core drilling equipment.
- ⚠ Toughened glass cannot be cut after toughening; the panel must be replaced with one pre-cut before the toughening process.
Can You Fit a Cat Flap in Double Glazed Glass?
Yes. a cat flap can absolutely be fitted into a double glazed glass panel. However, it is not a DIY job. Double glazed units consist of two panes of glass with a sealed air or gas gap between them. Cutting through both panes requires specialist core drilling equipment and must be carried out by a qualified glazier.
When done correctly the result is clean, professional and permanent. The cat flap sits flush within the glass panel with no visible housing on either side, one of the neatest installation options available for any home. The Glass & Glazing Federation recommends always using a qualified glazier for any glass cutting work, particularly on sealed double glazed units. For the full installation process, see our guide to fitting a cat door in glass.
Important: Toughened or tempered glass cannot be cut after it has been toughened. If your double glazed unit contains toughened glass, the hole must be cut before the toughening process, which means the glass panel will need to be replaced rather than retrofitted. Always check with your glazier before proceeding.
How the Installation Works
A glazier will use a core drill to cut a round hole through both panes of the double glazed unit simultaneously. This is where Pet-Tek's round cut-out design delivers a major advantage: a round hole is significantly faster and easier to drill cleanly than a rectangular cut, and eliminates the stress fracture risk that comes with cutting corners in glass. For a complete step-by-step walkthrough, see our how to fit a cat door in glass guide.
- The glazier measures and marks the cut-out position, typically in the lower portion of the panel at the correct height for your cat
- A core drill cuts through both glass panes in a single pass
- The cut edges are dressed and cleaned
- The Pet-Tek cat flap unit is inserted and secured with the retaining ring
- Silicone seal is applied around the outer ring to weatherproof the installation
Most experienced glaziers complete the full installation in under an hour. The round cut-out means no corner grinding, no stress fractures, and a clean finish every time.
Which Pet-Tek Models Suit Double Glazing?
All Pet-Tek Catwalk® glass fitting cat door models are compatible with double glazed units. The Catwalk® cat door range accommodates glass panels from 3mm up to 28mm thick: covering the vast majority of standard double glazed units used in residential homes across New Zealand, Australia, the UK and beyond. If you also need to stop neighbourhood cats entering, the multi-magnetic glass fitting model (G-MCDW) provides battery-free selective entry for glass panels up to 26mm thick.
| Glass Type | Typical Thickness | Pet-Tek Compatible |
|---|---|---|
| Single glazing | 3mm – 6mm | ✓ Yes |
| Standard double glazing | 14mm – 24mm | ✓ Yes |
| Triple glazing | 28mm – 36mm | ✓ Yes (up to 32mm) |
| Toughened glass | 6mm – 12mm | ✓ Yes (cut before toughening) |
| Laminated glass | 6mm – 12mm | ✓ Yes |
Dog Doors in Double Glazing — The Dogwalk® Range
Double glazing installations aren't just for cats. The Dogwalk® glass fitting dog door range uses the same round cut-out, glazier-installed approach, scaled up for dogs. The dual glaze models are engineered specifically for double glazed panels:
| Model | Suits | Glass Thickness | Flap Size | Cut-Out |
|---|---|---|---|---|
| Standard Dual Glaze (G-DDC / G-DDW / G-DDB) | Medium to semi-large dogs | 3–32mm | 270×313mm | 385mm dia |
| Intermediate Dual Glaze (G-IDDC / G-IDDW / G-IDDB) | Small to medium dogs | 4–32mm | 216×250mm | 320mm dia |
The installation process is identical to the cat door process above: a glazier core-drills a single round hole through both panes and the unit seals flush on both sides. Because dog door cut-outs are larger (320mm or 385mm diameter), confirm your glass panel has enough clearance from the frame edges before ordering. Your glazier can verify this from the cut-out specification.
Will It Affect My Home's Insulation?
This is the second most common concern, and a valid one. Any opening in a glass panel will reduce its thermal performance to some degree. However, Pet-Tek cat flaps are engineered to minimise heat loss through several design features: Two build details do the quiet work here: the flap sits in its body at next to zero tolerance behind a full brush seal, and the internal draft angles are shaped so rain that gets driven into the frame drains back out instead of pooling. A sealed unit deserves a door built to the same standard.
- Brush seals around the flap opening trap air and block drafts
- Close-fitting polycarbonate flap with magnetic closure creates a tight seal when not in use
- 4-way manual locking allows you to fully lock the flap shut in winter or when you are away
- Precision moulded housing fits flush against both glass surfaces with no gaps
While no pet door matches the insulation of an uncut panel, Pet-Tek's glass fitting models are among the most thermally efficient available. See our full guide on keeping your home warm with a pet door.
Where Should the Cat Flap Be Positioned?
The centre of the cat flap opening should sit at approximately 15–20cm above ground level for most cats: high enough to keep out drafts and small animals, low enough for easy access. For older cats or cats with mobility issues, position it closer to ground level.
Always measure your cat's shoulder height before confirming the installation position with your glazier. Not sure what size opening your cat needs? Use our interactive size guide to find the right model for your cat's measurements, or read our full pet measuring guide.
Need help working out the right size for your cat? Our size calculator takes your cat's weight and recommends the exact right Catwalk® model. Find My Pet Door →
Finding a Glazier for the Job
Pet-Tek products are used by glaziers across New Zealand, Australia, the UK, and 20+ countries worldwide. If you need help finding a local glazier familiar with Pet-Tek installations, contact us and we'll do our best to point you in the right direction.
When briefing your glazier, let them know:
- The exact model of Pet-Tek cat flap you have purchased (they can confirm the cut-out diameter)
- The thickness and type of your glass panel
- Whether the glass is toughened or laminated
- The desired position: height from floor and distance from frame
Frequently Asked Questions
Ready to find the right cat flap for your glass?
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