How a Double-Glazed Pet Door Unit Is Made, From Measurement to Sealed Unit

When owners hear that a pet flap can go into a double-glazed door, the first question is usually how — the second is whether the result is a proper sealed unit or a compromised one. The answer is that a double-glazed pet door is not a standard unit with a hole knocked in it. It is a unit built from the start to contain a flap, using the same processes as any replacement double glazing, with the opening planned before the glass is even toughened. This article walks through how double-glazed pet door units are made, stage by stage, so you can see exactly where double glazed pet door unit fabrication differs from ordinary glazing — and where it deliberately does not.

Why the opening has to exist before tempering

Everything starts with a constraint of physics. Tempered (toughened) glass gets its strength from heat treatment that locks stresses into the sheet. Once tempered, it cannot be cut, drilled or ground — attempt it and the whole pane shatters into granules by design. So the flap opening in each pane can only be formed while the glass is still in its raw, annealed state. That single fact dictates the whole fabrication sequence: the shape of your new unit, including its hole, is finished before the strengthening happens, and no part of the process can be improvised on site in your doorway.

Double glazed pet door unit fabrication, step by step

Step 1: Measurement and template

Your existing unit is measured in the frame: overall size, glass thickness, and the position the flap needs to occupy — set by your pet. Dog flaps follow the standard sizes, Medium 23×35 cm, Large 28×45 cm and X-Large 36×65 cm; cats over 4 kg take a Large flap. The flap position is marked relative to the bottom of the panel so your pet steps through at the right height once the unit is in the door.

Step 2: Cutting and forming the opening

Two panes are cut to size from raw glass, and the flap aperture is cut into each one at the templated position. Edges are finished smooth — the aperture’s edge quality matters, because flaws in glass become weak points under stress.

Step 3: Tempering

Each pane is then heat-treated in the tempering furnace. The glass, hole and all, comes out as safety glass: far stronger than annealed glass, and made to break safely if it ever fails. This is the point of no return in the process, and the reason measuring twice at Step 1 is not a figure of speech.

Step 4: The flap is fitted to the first pane

The pet door — a microchip model from SureFlap or PetSafe, a manual flap, or a Hakuna Pets or PetSafe dog door with its magnetic seal — is mounted into the aperture of the inner pane and sealed around its frame. Fitting it at the bench, with the pane flat and accessible from both sides, produces a neater and better-sealed result than any in-situ work could.

Step 5: The unit is sealed

The two panes are assembled with the spacer bar around the perimeter and sealed as a single double-glazed unit, exactly as a standard replacement unit is made: a cavity of dry air (or gas fill where specified) between the panes, edge seals keeping moisture out. The flap passes through both panes, and the sealed perimeter of the unit is uninterrupted — the unit insulates and behaves like the one it replaces because, constructionally, it is the same thing with an appliance built into it.

The swap at your home

Fabrication happens away from your home; fitting is a swap. Your existing unit is deglazed and removed, the new unit is set into the same frame and glazed in, and the beads and seals are made good. Your original glass is not destroyed — it is kept and stored, and if you are renting, that is the heart of the arrangement: at move-out, your original unit goes back and the swap-back takes about 30 minutes, with no landlord NOC needed at any stage, because the landlord’s glass was never cut. While we are on honesty: if your existing glazing is reflective or tinted, the new unit’s shade is matched as closely as possible, but a 100% identical match to the original supplier’s coating cannot be guaranteed — we will discuss it before fabrication, not after.

Frequently asked questions

How long does the whole process take from measurement?

The fabrication is a made-to-order sequence — cutting, tempering, assembly — so it runs to days rather than the same-day fitting possible with a standard white sliding insert booked before 10 AM. We confirm the timescale for your unit before you commit, and the fitting visit itself, once the unit is ready, is a single appointment.

Is a unit with a flap in it as strong as a plain unit?

The glass is tempered safety glass made by the same process as the plain unit it replaces, and the flap sits in an aperture that was formed before tempering, not forced afterwards. The flap assembly itself is the moving part, as it is in any pet door; the glazing around it is proper sealed-unit construction.

Can any double-glazed door have a unit made for it?

Most residential doors, yes — single openable doors, fixed panels and sliding door panels can all be re-glazed this way. The limits are practical: very unusual shapes or units we cannot safely remove and replicate. Photographs and the measurement visit settle it before anything is ordered.

Where does my original glass go?

It is removed intact, labelled and stored, so that it can be refitted when you move or sell. That storage is what makes the installation fully reversible and protects a tenant’s deposit.

Can I choose a bigger flap later without a new unit?

The aperture is made for a specific flap size, so changing size means remaking the unit — one reason we size carefully at the start, including sizing cats over 4 kg into a Large flap and choosing the dog size for the adult dog, not the puppy.

Start with the measurement

Double glazed pet door unit fabrication begins with us seeing your door. WhatsApp photographs of the door and its panel to +971 52 443 2655 and we will confirm that a fabricated unit suits it and talk you through the sequence for your home. Prefer email? Write to admin@petdoorfix.com. We fabricate and fit across Dubai, Abu Dhabi and all seven UAE emirates.

Next guide: Will a Pet Door Make My Double Glazing Mist Up? Condensation and Sealed Units Explained