Standard Window Sizes in Canadian Homes: A Renovator's Cheatsheet
Too Long; Didn't Read
- The Myth: "Standard" means I can buy it off the shelf at Home Depot.
- The Reality: 95% of window replacements are custom-sized to the 1/8th inch.
- The Exception: New construction uses strictly modular sizes (e.g., 24x36).
- The Code: Egress windows in bedrooms must provide an unobstructed opening of 0.35 m² (3.8 sq ft).
Answer First: In post-war Toronto bungalows (1950s-70s), the most common window size is 24 inches x 36 inches for basements and bathrooms. However, do not frame a rough opening based on a blog post. Always frame the opening 1 inch wider and 1 inch taller than your actual window unit size.
You stand in the aisle at a big box store, tape measure in hand, looking for a 30x60 window. They have 29.5x59.5. They have 31x61. They do not have yours.
This scene frustrates DIY renovators across Canada. Unless a large subdivision developer built your house in the last 10 years, your windows are likely not "standard."
The Truth Table: Common "Stock" Sizes
While custom is king for renovations, you will most commonly find these sizes in the wild.
| Window Type | Common Widths (Inches) | Common Heights (Inches) | Best For... |
|---|---|---|---|
| Single/Double Hung | 24, 28, 32, 36 | 36, 40, 48, 60, 72 | Bedrooms, Hallways |
| Casement | 24, 28, 30 | 36, 48, 60, 72 | Living Rooms, Kitchens |
| Slider (Basement) | 30, 32, 36 | 12, 16, 24 | Basements (High ups) |
| Patio Door | 60 (5ft), 72 (6ft) | 80 (Standard Height) | Backyards |
The "Rough Opening" Logic
When framing a new wall, you need the Rough Opening (R.O.), not the window size.
- The Golden Rule: R.O. = Window Size + 1/2 inch to 1 inch.
- Why? Wood moves. Houses settle. Vinyl expands. That 1/2 inch gap allows us to shim the window perfectly square, even if your framing is slightly crooked.
- Insulation: We fill that gap with low-expansion foam to seal the envelope.
Mandatory Code: The "Egress" Rule
If you are turning a basement into a rental suite or just adding a bedroom, the Code is non-negotiable in Ontario (OBC 2024).
Bedroom windows must serve as an emergency exit.
- Minimum Opening Area: 0.35 m² (3.77 sq ft).
- Minimum Dimension: No dimension can be less than 380mm (15 inches).
- The Trap: A sliding window only opens half-way. To get a 15-inch opening, the window needs to be 30+ inches wide. This is why Casement windows (which crank open fully) are the king of basements.
The Installix Angle
Why do we measure to the millimeter?
Because a "standard" window in a non-standard hole relies on massive caulking beads to hide the gaps. Massive beads shrink, crack, and leak within 3 years.
We custom order every window to fit your brick opening, leaving a tight 1/4 inch tolerance for the longest-lasting seal possible.
Renovating? Get the Framing Right.
Don't frame your wall until you've chosen your window. Send us your blueprints for a free consultation.
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