Guide · · 3 min read
How to install a cat door in glass: what your glazier does, step by step
A round hole, two frame halves and six screws. Here is exactly what happens when a cat door goes into glass, so you know what you are paying the glazier for.
By the Pet-Tek International team, Auckland — designers of Catwalk® and Dogwalk® since 1999.
You will not be doing this yourself — cutting glass is a glazier’s job — but knowing the steps makes the quote make sense and the result better.
Before anyone cuts anything
- Buy the door first. The glazier needs the cut-out size, and it comes from the door you choose: Standard 245 mm (single glazing 3–10 mm), Maxi 267 mm (single or double, 3–28 mm), Multi-Magnetic 245 mm (3–26 mm), SureFlap 212 mm with its adaptor.
- Pick the pane. The fixed pane of a slider is best; it never moves. In the sliding pane, keep clear of the handle side.
- Mark the height. Bottom of the opening 100–150 mm off the floor. Mark it on the glass from outside with a wax pencil.
- Check single or double. Look at the pane’s edge. One sheet is cut in place; two sheets means a new unit.
Single glazing: cut in place
The glazier scribes the circle, scores it with a core drill or a circle cutter, and taps the disc out. The edge is arrised so it is not sharp. Twenty minutes for an experienced hand, and the pane stays in the frame throughout. Annealed glass only — if the pane is toughened (look for a small stamp in a corner) it cannot be cut and is replaced instead.
Double glazing or toughened: a new pane
The glazier measures the unit, orders a replacement with the hole cut in both sheets before toughening and sealing, and fits it a week or two later in the same frame. Your existing unit is not touched until the new one is on site. For a cat the door here is the Maxi Dual Glaze or Multi-Magnetic; the Standard is for single glazing.
Fitting the door: fifteen minutes
- Outer frame into the hole from outside, gasket against the glass.
- Inner frame over it from inside.
- Fixing screws cut to the glass thickness and tightened evenly — firm, not crushing.
- Caps on the screw heads.
- Turn the 4-way dial through all four positions. It comes fitted; nothing to assemble.
The glazier usually does this while on site; if not, it is a screwdriver job you can do yourself. The video on each product page shows it.
Dog doors: same steps, bigger hole
Dogwalk® Intermediate 320 mm, Medium 385 mm. Choose Dual Glaze for a sealed unit, Slim Line for single glazing and sliders. Our double-glazing guide covers the dog side in detail.
Three things that go wrong
Hole too close to the edge — the glazier sets the minimum distance; too close and the pane can crack. Door bought after the hole — the hole then dictates the model instead of the cat. Over-tightened screws — the frames clamp; they do not need to crush the gasket.
Questions on cost, cities and glazier quotes are in pet door installation in NZ and the FAQ.
Quick answers
How do you install a cat door in a glass door?
A glazier cuts a round hole in single glazing with a core drill, or orders a new double-glazed unit with the hole made. The outer frame goes in from outside, the inner frame over it from inside, and the screws clamp the two through the glass. The lock comes fitted.
What size hole for a cat door in glass?
245 mm for the Catwalk Standard, 267 mm for the Maxi, 212 mm for the SureFlap Microchip with its adaptor. The number is on each product page and on the printable sheet.
Can you cut a hole in toughened glass for a cat door?
No. Toughened glass cannot be cut after toughening; the glazier orders a new pane with the hole made before it is toughened. The same applies to double-glazed units.
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