Installation Guide

How to Fit a Cat Door in Glass — The Complete Glazier & Homeowner Guide

By Pet-Tek Editorial Team · July 2026 · 7 min read

Cat using a Pet-Tek Catwalk glass fitting cat door installed in a glass panel

Fitting a cat door in glass is one of the cleanest, most professional-looking installations you can have: a round hole, a flush-fitting unit, and no visible framing. It is also the most misunderstood. This guide covers the complete process: what the glazier does, what you can do yourself, how toughened and double glazed glass changes the job, and exactly what cut-out size each Catwalk® model needs. For an overview of both glass and wood installation, see our cat door installation guide.

Key Takeaways

A glazier cuts one round hole with a core drill, then fitting the Pet-Tek door unit itself takes minutes and can be done by the homeowner.
Toughened glass cannot be cut after toughening; a replacement panel with the hole pre-cut is made instead. Your glazier organises this.
Catwalk® glass fitting cat doors use a 245mm round cut-out (standard and multi-magnetic) or 267mm (maxi models), and suit glass from 3mm to 28mm depending on the model.

Can a Cat Door Be Fitted in Glass?

Yes — glass panels are the most common cat door installation location in New Zealand and Australia, and the entire Catwalk® glass fitting range is purpose-built for it. Single glazing, double glazing, ranch sliders, patio doors, and fixed glass panels are all suitable. The one hard rule: cutting glass is a glazier's job. The hole must be drilled with specialist core drilling equipment; attempting it with DIY tools will crack or shatter the panel.

The good news is that the glazier's part is a single round hole. Everything after that (fitting the door unit, the retaining ring, and the seal) is straightforward and can be done by you. The Glass & Glazing Federation recommends a qualified glazier for all glass cutting work.

Before You Book a Glazier — 4 Things to Confirm

Your glass type: single glazed, double glazed, laminated, or toughened. If you're not sure, your glazier can identify it on site. Toughened glass changes the process (see below).
Your glass thickness: measure at an open edge or ask your glazier. Each Catwalk® model has a specific glass thickness range (see the model table below).
Your model and its cut-out size: the glazier needs the exact cut-out diameter before drilling: 245mm for standard and multi-magnetic cat doors, 267mm for maxi models.
Your cat's measurements: shoulder height and widest body width plus 25mm each. See the measuring guide or use the door finder.

Why the Round Cut-Out Matters

Most imported glass fitting pet doors require a rectangular cut-out. Rectangles are slow to cut in glass and every corner is a stress point where cracks can start, both during cutting and years later. Pet-Tek's entire glass fitting range uses a round cut-out: a single pass with a core drill, no corners, no stress fractures, and a faster, cheaper job for the glazier. It is the reason glaziers across NZ, Australia and the UK prefer fitting the Pet-Tek range. The precision continues past the cut-out: the flap is machined to sit in its body at next to zero tolerance with a full brush seal over the gap, which is why a freshly fitted glass panel with a Catwalk® in it reads barely different on a draught test to the plain panel it replaced.

The Installation — Step by Step

Confirm the position: the bottom of the flap opening should sit roughly 15–20cm above floor level, and the cut-out needs clearance from the panel edges and frame. Your glazier will confirm both.
Mark the cut-out: using the diameter for your model (245mm or 267mm), the glazier marks the centre point and circle on the glass.
Core-drill the hole: a diamond core drill cuts the round hole in a single pass. On double glazing, both panes are drilled together.
Dress the edges: the cut edge is smoothed and cleaned so the door unit seats flush.
Fit the door unit: the Catwalk® unit inserts through the hole from the outside; the retaining ring secures it from the inside. This step is simple enough for the homeowner to do.
Seal and test: a bead of silicone around the outer ring weatherproofs the installation. Test the flap swing and the 4-way lock, and the job is done.

An experienced glazier completes the whole job in under an hour. Full fitting instructions are included with every door and available on each product page as a PDF download.

Watch the install — then give your glazier this

Round cut-out size: 245mm (original & multi-magnetic) or 267mm (maxi)
Your glass type & thickness: single or double glazing, 3–28mm
The fitting instructions from the box — glass range and clamping detail

Any qualified glazier can do this — most complete it in under an hour.

Toughened glass? Different path, same result. Toughened (tempered) glass cannot be cut after the toughening process; drilling it will shatter the panel. Instead, your glazier orders a replacement panel with the hole pre-cut before toughening, then swaps the panels. Ranch sliders and patio doors are almost always toughened, so this is the normal route for sliding door installations. See our full guide to cat flaps in double glazed glass for sealed-unit specifics.

Which Model, Which Cut-Out, Which Glass?

Catwalk® glass fitting cat doors — cut-out and glass compatibility
Model	Cut-Out	Glass Thickness	Flap Size
G-CDC / G-CDW, original	245mm dia	3–10mm	193×165mm
G-MCDW, multi-magnetic selective entry	245mm dia	3–26mm	170×155mm
G-SDDSLC / G-SDDSLW, maxi slim line	267mm dia	3–21mm	203×187mm
G-SDDC / G-SDDW / G-SDDB, maxi dual glaze	267mm dia	3–28mm	203×187mm

Single glazing? The original G-CDC or G-CDW is the fastest install. Double glazing? Choose the maxi dual glaze models for the widest glass range, or the G-MCDW if you also need to keep other cats out. For a full comparison of every model, see our best glass fitting cat and dog doors guide. Fitting a door for a dog instead? The Dogwalk® glass fitting range uses the same round cut-out process with larger diameters.

Finding a Glazier

Pet-Tek products are fitted by glaziers across New Zealand, Australia, the UK and 20+ countries; most glaziers know the range and its cut-out sizes well. When you call, tell them: the model you've purchased, the cut-out diameter, your glass type and thickness, and the position you want. If you need help finding a glazier familiar with Pet-Tek installations in your area, contact us.

Frequently Asked Questions

Can I cut the hole in the glass myself?

No — glass cutting requires a diamond core drill and glazier training. Attempting it with DIY tools will crack or shatter the panel. The part you can do yourself is fitting the door unit after the hole is cut: insert the unit, secure the retaining ring from the inside, and apply the silicone seal.

What size hole does the glazier need to cut?

245mm diameter for the standard cat doors (G-CDC, G-CDW) and the multi-magnetic G-MCDW, or 267mm diameter for the maxi models (G-SDDSLC, G-SDDSLW, G-SDDC, G-SDDW, G-SDDB). The cut-out size is also printed in the fitting instructions included with every door.

Can a cat door be fitted in an existing double glazed unit?

Yes — provided the glass is not toughened, the glazier core-drills both panes of the sealed unit together and the door unit seals the cut-out point. If either pane is toughened, a replacement unit with the hole pre-cut is made instead. See our double glazing guide for full details.

My ranch slider is toughened glass: what happens?

Toughened glass cannot be drilled; it shatters. The standard process is a replacement panel: the glazier measures your slider, orders a new toughened panel with the round hole cut before toughening, and swaps the panels. This is routine work for glaziers and the standard route for nearly all sliding door installations.

How long does the installation take?

For glass that can be cut on site, most experienced glaziers complete the whole job (drilling, dressing and fitting) in under an hour. For toughened glass, the replacement panel needs to be manufactured first, so allow the glazier's normal panel lead time plus a short fitting visit.

Where in the panel should the hole go?

The bottom of the flap opening should sit roughly 15–20cm above floor level for most cats, lower for older or less mobile cats. The cut-out also needs clearance from the panel edges and frame; your glazier will confirm the minimum edge distance for your glass type before drilling.

Will the hole weaken my glass panel?

A properly drilled round hole with dressed edges does not create the corner stress points that rectangular cut-outs do, which is exactly why Pet-Tek uses a round profile. The fitted door unit and seal also reinforce the cut-out area. Panel integrity is a question your glazier assesses before cutting, including edge clearances.

Is the process the same for a dog door in glass?

Yes — identical process, larger hole. Dogwalk® glass fitting dog doors use a 320mm cut-out (intermediate models) or 385mm cut-out (standard models), with the same round core-drill method and the same toughened glass replacement-panel rule.

Are spare parts available if the flap wears out years later?

Yes — replacement flaps, retaining rings, locking dials and seals are available directly from Pet-Tek for all current glass fitting models, including models manufactured over 20 years ago. The glass hole never needs to be re-cut; only the unit components are replaced.

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