How to Tell If Your Glass Door Is Double-Glazed Before You Book a Pet Door

Before you book a pet door for a glass door or window, one question decides which installation route applies to you: is my glass door double glazed, or is it a single pane? The answer changes how the panel is made, so it is worth checking before anything is ordered. Our guide to how to tell if your door is double-glazed covers the glazed routes in full, but you can settle the question yourself in a few minutes with the four checks below — no tools beyond a tape measure and your phone torch.

Is my glass door double glazed? The four checks

Double glazing means two panes of glass sealed into one unit with a narrow gap between them, usually filled with air or an insulating gas. Single glazing is just one pane. The two look similar from across a room, but up close they give themselves away in several ways.

Check 1: Look for the spacer bar at the edge

This is the most reliable check. Open the door or look at the edge of the panel where the glass meets the frame, and look closely at the perimeter of the glass itself. A double-glazed unit has a spacer bar — a slim metal or dark strip, often silver, black or white — running between the two panes around all four edges, set slightly back from the glass edge. You are looking at the sandwich edge of the unit: glass, spacer, glass. A single pane has no spacer and no second layer; the edge is simply one thickness of glass meeting the frame’s seal. On many units you may also see small markings or a brand stamp printed near a corner of the glass, which is a further clue you are dealing with a manufactured sealed unit.

Check 2: The two-reflection test

Hold your phone torch, a lighter or even a finger close to the glass and look at the reflection at an angle. A single pane gives you one clear reflection. A double-glazed unit gives you two reflections, slightly offset from each other — one from the outer surface of the first pane and one from the second pane behind it. Move your light source slowly and the doubled reflection is easy to spot, especially in the evening when the room is lit and the garden is dark. If the two reflections appear tinted slightly differently, that is normal: one pane sometimes carries a reflective coating, which is also why we can never guarantee a 100% identical shade match on reflective glass — the closest options are shown to you before anything is made.

Check 3: Measure the panel thickness

Look at the glass edge where it enters the frame, or measure across an exposed edge if your door design allows it. A single pane in a door is typically just a few millimetres of glass. A double-glazed unit is noticeably thicker — two panes plus the gap between them — and feels like a slab rather than a sheet. Thickness alone is not proof on its own, because thick single panes exist, but combined with a spacer bar it is conclusive.

Check 4: Tap and listen

Knock gently on the glass with a knuckle. A single pane tends to ring with a thinner, sharper sound and can flex or vibrate slightly. A double-glazed unit sounds duller and feels more solid, because the sealed unit is stiffer and the second pane damps the vibration. Treat this as supporting evidence rather than the verdict — but once you have tapped both types, the difference is hard to unhear.

Why the answer changes your pet door route

A pet door in glass is never cut into your existing pane on site. Toughened glass cannot be cut after manufacture without shattering, so in both cases the flap is fitted into a new, made-to-measure replacement panel — what changes is what that panel has to be. If your door is double-glazed, the replacement is a factory-made sealed unit, built as two panes with the spacer and seal intact, so the door keeps its insulation and does not mist up. If your door is a single pane, the replacement panel is simpler and quicker to produce. Sliding doors are a separate route again: a pet door insert sits in the track alongside your existing slider, and in a standard white aluminium frame with clear glass it can be fitted the same day if booked before 10 AM, with custom RAL powder-coating taking 2–3 days.

Either way, the rental position is the same. Your original glass is removed whole, stored safely and swapped back in 30 minutes when you move out, so the fitting is 100% rental-friendly with no landlord NOC needed.

A practical pre-booking checklist

Once you have run the four checks, gather the details that let us confirm your route from photos alone:

• A photo of the full door or panel from inside, showing the frame and any handles or locks.
• A close-up of the glass edge showing the spacer bar if there is one — this single photo often settles the double-glazing question on its own.
• A close-up of any stamp or markings in the corner of the glass.
• The panel’s approximate width and height, measured frame to frame.
• Your pet’s details — for dogs, the size they need (Medium 23×35 cm, Large 28×45 cm or X-Large 36×65 cm), and for cats, their weight, because cats over 4 kg need a Large flap.

Send those through and we can tell you which route your door needs, and how the panel will be made, before anyone visits.

Frequently asked questions

Can I check for double glazing without opening the door?

Yes. The reflection test and the spacer bar are both visible on a closed door in most cases — check the perimeter of the glass from inside, where the pane meets the frame, and run the two-reflection test after dark, when it shows up best.

My door has a spacer bar but the glass looks like one pane. What does that mean?

You are almost certainly looking at a double-glazed unit. From face-on, a sealed unit can look like a single sheet because the two panes sit so close together; the spacer bar at the edge is the giveaway.

Does double glazing rule out a pet door?

Not at all. It simply means your flap goes into a factory-made double-glazed replacement unit rather than a single-pane panel. The new unit is sealed exactly like the original, so the door’s insulation is preserved and your uncut original glass is stored for swap-back.

What if one of my doors is double-glazed and another is not?

That is common in UAE homes, where extensions and replaced panels often differ from the original build. Each panel is made to match what it replaces, so a double-glazed door gets a sealed unit and a single-glazed panel gets a single panel — send photos of each door and we will confirm both.

I rent. Does checking matter for my deposit?

The checks protect it. Because your original pane is stored whole and swapped back in 30 minutes at move-out, the door is returned exactly as you found it — no landlord NOC required.

Not sure what your glass is? Send us a photo

If you are still asking is my glass door double glazed after the four checks, WhatsApp us on +971 52 443 2655 with a photo of the glass edge and the full door, and we will confirm your glazing type and the right pet door route for it. You can also email admin@petdoorfix.com. We fit pet doors in glass across all seven UAE emirates.

Next guide: Installing Pet Doors in Reflective Villa Glass: Our Honest Guide to Tint & Shade Matching