Too Long; Didn't Read
- The Catch: You cannot cut tempered glass. Any attempt shatters it instantly.
- The Process: The cutout must be made in raw glass before it goes into the tempering oven.
- The Cost: Expect $350-$700 for a new tempered glass panel with a mail slot cutout, plus hardware.
- Canada Post Rule: Door slots must be at least 17.5 cm x 4 cm (about 7" x 1.6") under SOR/83-743.
- The Bottom Line: You are not "adding a slot." You are ordering a new glass unit.
Answer First: You cannot cut a mail slot into an existing glass door. Tempered glass -- the only type allowed in doors by the Ontario Building Code -- shatters on contact with any cutting tool. The slot must be cut into raw glass before it enters the tempering oven, which means you need an entirely new glass panel fabricated to spec. At Installix, we order the glass with the cutout already made, temper it, and swap out your old panel. Budget $550-$1,150 all-in for a Toronto residential door.
Why You Cannot "Just Cut a Hole"
This is the single most important thing to understand about this project, and it is the reason most DIY attempts end with a pile of glass cubes on the porch.
Tempered glass is not regular glass. During manufacturing, the panel is heated to roughly 620°C and then blasted with jets of cold air. This locks the outer surface into compression and the interior into tension. The result is glass that is four to five times stronger than annealed (raw) glass and, critically, glass that breaks into small blunt granules instead of jagged shards.
That internal tension is also why you cannot modify it. The moment a cutting wheel, drill bit, or grinder touches the surface, the stress equilibrium collapses. The entire panel does not crack. It explodes. Every single time. There is no "careful" way to do it. There is no special blade. There is no YouTube hack.
The glass must be cut before tempering. Period.
This means that adding a mail slot to a glass door is really a glass replacement project. You are ordering a new panel, cut to the exact dimensions of your door frame, with a rectangular cutout positioned where you want the slot, and then sending that panel through the tempering oven.
What About Laminated Glass?
Some homeowners ask about laminated glass as a workaround. Laminated glass (two layers bonded with a plastic interlayer) can technically be cut after fabrication, but it is not commonly used in residential entry doors in Ontario. The Building Code requires safety glazing in doors, and while laminated qualifies, most door manufacturers default to tempered. Even if you cut laminated glass successfully, the exposed edges around the slot would need polishing and sealing -- a fussy, fragile result. We do not recommend it.
The Correct Process (Step by Step)
Here is how we handle a mail slot installation at Installix. No shortcuts.
Step 1: Measure the Existing Glass
We measure your current glass panel -- width, height, and thickness. Most residential glass doors in Toronto use 5 mm or 6 mm tempered glass. Some heritage homes in neighbourhoods like The Annex or Roncesvalles have thicker panels. The measurement must be precise to the millimetre because tempered glass cannot be trimmed on site.
Step 2: Choose the Hardware
The mail slot hardware determines the cutout dimensions. You pick the slot first, then we cut the glass to match. Common options in 2026:
| Hardware | Slot Opening | Material | Price Range |
|---|---|---|---|
| CRL MS125 | 10-1/4" x 1-7/8" | Extruded Aluminum | $45-$70 |
| CRL 933 Deluxe | 14" x 2" | Extruded Aluminum | $65-$100 |
| Deltana MS0030 | 11" x 2" | Solid Brass | $90-$150 |
| FHC FHCMS13 | 10-1/4" x 1-7/8" | Aluminum | $40-$60 |
All of these exceed the Canada Post minimum of 17.5 cm x 4 cm (about 7" x 1.6") required under the Mail Receptacles Regulations (SOR/83-743). Go with the CRL if budget matters. Go with the Deltana if you want solid brass that will patina nicely on a heritage door.
Step 3: Order the Glass
We send the measurements and cutout specs to our glass fabricator. The cutout is made in annealed glass using a CNC waterjet or diamond-blade bridge saw. Corners are radiused (rounded) to prevent stress fractures during tempering. Then the panel goes into the oven.
Turnaround in the GTA is typically 5-7 business days for a standard panel. Custom tints, Low-E coatings, or obscure glass add a few days.
Step 4: Swap the Panel
Our glazier removes the old glass, cleans the frame, applies fresh glazing tape or silicone, and sets the new panel with the cutout. The mail slot hardware gets mounted through the opening with silicone on both sleeves to create a weather seal.
Total on-site time: about 45 minutes to an hour.
If you want to start this process, visit our glass replacement page or call us directly.
Canada Post Requirements You Should Know
Before you commit to hardware, make sure your slot meets federal regulations. Canada Post does not care about your aesthetic preferences. They care about whether their carrier can shove a Canada Revenue Agency envelope through your door without bending it.
Under the Mail Receptacles Regulations (SOR/83-743):
- Door mail slots must have a minimum opening of 17.5 cm wide x 4 cm tall (roughly 7" x 1.6").
- The slot must be positioned between 60 cm and 150 cm from the ground (about 24" to 59").
- The slot must be accessible without climbing stairs that lack a handrail.
Most commercial mail slot hardware comfortably exceeds the minimum width. The height is the measurement to watch. A 1-7/8" (47.6 mm) opening clears the 4 cm minimum, but just barely. If your carrier delivers thick flyers or small parcels, the Deltana MS0030 with its 2-inch opening is more forgiving.
Pro tip: If you live in a Toronto neighbourhood with community mailboxes (most new builds in Scarborough, Etobicoke, and North York), you may not even receive door delivery. Check with Canada Post before spending money on a slot nobody will use.
Cost Breakdown for Toronto / GTA (2026)
Let's talk real numbers. Here is what a typical mail slot glass door project costs in 2026 in the Greater Toronto Area:
| Component | Cost Range |
|---|---|
| New tempered glass panel (5-6 mm, clear, with cutout) | $350-$700 |
| Mail slot hardware (CRL or Deltana) | $40-$150 |
| Glazing labour (removal + install) | $150-$300 |
| Total | $540-$1,150 |
The wide range depends on glass size (a full-length sidelite costs more than a half-lite), thickness, and whether you want Low-E or tinted glass. Obscure (frosted) glass with a cutout tends to run about 15% more than clear.
Is it cheap? No. But compare it to replacing the entire door, which runs $1,500-$4,000+ for a quality fibreglass or steel unit with glass inserts. If the door itself is in good shape, swapping just the glass panel is the cost-effective move.
For a full door replacement quote, check our residential door replacement page.
When a Mail Slot Is the Wrong Call
We install mail slots regularly. We also talk people out of them regularly. Here is when you should skip the slot entirely:
1. You have a high-efficiency door and care about your gas bill. A mail slot is a hole in your building envelope. Even the best draft-free models with spring-loaded interior and exterior flaps let in cold air. In a Toronto January, that is -20°C air finding its way into your foyer. If you spent money on a well-insulated entry door, punching a hole in it is counterproductive.
2. You have pets. Dogs and mail carriers have a famously adversarial relationship. A mail slot at nose height is an invitation for your retriever to bite a Canada Post worker's fingers. This is not a joke -- it is a genuine liability issue, and Canada Post can suspend your delivery.
3. You have a community mailbox. As mentioned above, many GTA subdivisions built after 2014 use centralized community mailboxes. Door delivery is not available. A mail slot on your door will collect nothing but spiders.
4. Security. A determined person can fish keys, reach deadbolts, or peer through a mail slot. Some Toronto insurance providers ask about mail slots during home assessments. A wall-mounted locking mailbox is more secure.
If any of these apply, save your money. A simple wall-mounted mailbox from Canadian Tire costs $30-$80 and requires no glass work.
The Installix Approach
We see a few calls per month from homeowners who want a mail slot added to their glass front door. The conversation usually starts with "Can you just cut a hole?" and we have to deliver the bad news.
But the good news is that the project is straightforward once you understand the constraint. We measure your existing panel, you pick hardware, we order tempered glass with the cutout already done, and we swap it in under an hour. No drama. No shattered glass on your porch.
We keep standard CRL mail slot hardware in stock on our trucks. For brass options like Deltana, we order to match your finish preference -- oil-rubbed bronze, satin nickel, polished brass, or antique brass.
If you are thinking about this project, get in touch for a quote. We service Toronto, Mississauga, Brampton, Vaughan, Markham, and the rest of the GTA.
You might also find these guides useful:
- Why Your Window Is Leaking: Riverbedding, Weep Holes, and Caulking
- Window Condensation: Inside, Outside, or Between
Frequently Asked Questions
Can I cut a hole in my existing tempered glass door for a mail slot?
No. Tempered glass cannot be cut, drilled, or ground after tempering. The internal stress pattern causes the entire panel to shatter into small fragments the moment you score it. The cutout must be made in raw (annealed) glass before it enters the tempering oven.
How much does it cost to add a mail slot to a glass door in Toronto?
Budget $350-$700 for a new tempered glass panel with the slot cutout, plus $40-$150 for the mail slot hardware. Installation by a glazier typically adds $150-$300. Total project cost in the GTA runs $550-$1,150 depending on glass thickness and door style.
What size does a mail slot need to be to meet Canada Post requirements?
Under the Mail Receptacles Regulations (SOR/83-743), a door mail slot must have a minimum opening of 17.5 cm x 4 cm (approximately 7 inches x 1.6 inches). Most commercial mail slot hardware exceeds this minimum, with standard CRL slots offering openings around 8-13 inches wide.
Is a mail slot in a glass door energy efficient?
Not particularly. Even draft-free models with spring-loaded flaps allow more air infiltration than a sealed glass panel. If energy efficiency is a priority, consider a wall-mounted mailbox instead. If you must have a door slot, choose a model with both interior and exterior flaps and apply weatherstripping tape around the sleeve.
Can I install a mail slot in a wood door with a glass insert instead?
Yes, and it is often easier. If your door has a solid wood rail at the bottom, a contractor can cut a slot directly into the wood without touching the glass. This avoids the cost of a new tempered panel entirely. However, if the glass extends to the bottom of the door, you are back to ordering custom glass.