Do You Need a Permit to Replace Windows or Doors in Ontario? Same Size No, Bigger Yes, Plus Egress, Safety Glass and the Property-Line Rule

Windows & Doors

Permits for Windows and Doors in Ontario: Same Hole, No Permit. Bigger Hole, Permit. And Three Rules That Apply Either Way.

The building department does not care that you are replacing eighteen windows, as long as each one goes back in the opening it came out of. It cares a great deal the moment an opening gets wider, taller, or new, because the wall above it is holding something up. Here is where the line is, what a permit involves, and the code rules that still apply to a straight replacement.

Ontario Building Code as in force October 2026; your municipality administers it and some have their own forms. When in doubt, a phone call to the building department is free.

No permit

  • Replacing a window or exterior door with one in the same rough opening, any style, any material.
  • Retrofit inserts, full-frame replacements, new sealed units, new hardware.
  • Replacing a patio door with a patio door of the same width.
  • Making an opening smaller (filling in part of it), in most municipalities, as long as egress and ventilation rules still work for the room.

Permit

  • Widening or raising an opening in an exterior wall: a new header, sized for the span and the load, with a permit drawing. Sidelights where there were none is the common one.
  • A new opening anywhere in an exterior wall or a bearing interior wall.
  • A new or enlarged basement window for a bedroom: egress, the well, the drainage and often the cut through concrete. The egress page has the dimensions.
  • A bay or bow window that projects past the wall with its own roof and floor; it is a small addition.
  • Large sliding or folding door walls replacing a window and part of a wall: header, posts, footings sometimes. Large glass doors.

The permit itself is $150 to $400 in most Ontario municipalities for this kind of work. The drawing is the real cost: a BCIN designer or an engineer sizing the header and detailing the bearing, $400 to $1,200. The contractor usually arranges it. A contractor who says “we do not bother with permits for this” is telling you they will not be there when you sell the house and the buyer’s lawyer asks.

Rules that apply with or without a permit

  1. Egress from bedrooms. Every bedroom needs a window that opens to at least 0.35 m2 (3.8 sq ft) with no dimension under 380 mm (15 in.), openable from inside without tools, unless the room has a door directly outside. Replacing a bedroom window with a smaller operable area, or a style that opens less, can break this. Casements usually pass; some sliders do not.
  2. Safety glazing. Glass in and beside doors, glass within about 24 in. of a door, glass that goes down near the floor, and glass in and around tubs and showers has to be tempered or laminated. The manufacturer handles it when the schedule says where the window goes; tell them.
  3. Energy performance. Ontario’s energy supplement to the code sets a minimum for windows in new houses and additions (a U-value around 1.6 W/m2K or an Energy Rating around 25, depending on the compliance package, and most new packages ask for better). Replacement windows are not usually inspected for it, but anything ENERGY STAR certified is well past it. The ratings.
  4. Glass near a property line. The code limits the area of unprotected openings in a wall close to the lot line, because fire spreads window to window. Enlarging a window in a wall 1.2 m (4 ft) from the neighbour can be refused outright. This is the rule that surprises people on narrow city lots and cottage lots.
  5. Ventilation. Rooms need openable area for natural ventilation unless mechanically ventilated. Turning every bedroom window into a fixed picture window is not allowed without the mechanical side.

Where homeowners go wrong

  1. Adding sidelights to a bearing wall with no permit. The header above the door was sized for 36 in. of opening, not 60. Headers sag slowly; the door stops closing in year three.
  2. Making the basement bedroom window “look nicer” and smaller. It is no longer a bedroom on paper, and the inspector on the sale will say so.
  3. Putting a big fixed picture window in the side wall 3 ft from the neighbour. The code says no, and the municipality can make you take it out.
  4. Letting the contractor “pull the permit later”. Later is never. Permit before the opening changes, drawing attached.

Questions people ask

Do I need a permit to replace windows in Ontario?

Not for same-size replacement. Yes for any change to the size or location of the opening.

Do I need a permit to replace a front door?

Same size, no. Adding sidelights, a wider door, or double doors where there was a single: yes, because the header changes.

Can I put a bigger window in my basement?

Yes, with a permit; it is one of the most common small permits there is. Cutting concrete, a steel or concrete lintel, a window well with a drain, and egress dimensions if the room is a bedroom.

Who sizes the header?

For ordinary spans in a house, a BCIN-registered designer can use the code’s span tables. For big openings, point loads, or anything unusual, an engineer. The building department will tell you which they want.

Budgeting the change

The door calculator carries a line for widening a bearing wall with the permit and header, and the window calculator assumes same-size openings unless you tell it otherwise. If you are enlarging, add $2,400 and a few weeks.

Price the windowsEgress windows

Sources and further reading