Replacing an interior door in Newmarket with one the same size needs no building permit. The one door that carries real rules is the one between your garage and the house, which must be weatherstripped and self-closing.
A door that sticks, sags or has a cracked slab is one of the smaller jobs in a house, and it is easy to overthink. Most of it is measuring well and picking the right type of replacement. A few rules sit around the edges, though, and they are worth knowing before you start.
Does a door swap need a permit in Newmarket?
No, as long as the opening stays the same. The Town of Newmarket's building page lists new or enlarged windows and doors, and the creation of new openings, as work that needs a building permit. It also says plainly that replacing a door or window with one the same size as the existing one does not need a permit.
The line is the opening itself. Widening a doorway for a bigger door, cutting a new one, or removing or moving a wall around it all fall into the permit side, because walls and structural changes do. Painting, floor finishes and decorating do not. If your job sits between those lists, the Town's Building division is at building.permits@newmarket.ca or 905-953-5300 ext. 2400, and asking costs nothing.
The garage-to-house door is not an ordinary interior door
If you have an attached garage, the door that leads into the house is the one to treat carefully. The Ontario Building Code, in Article 9.10.13.15, has long required a door between an attached garage and a dwelling to be tight-fitting and weatherstripped so it works as a barrier against exhaust fumes, and to be fitted with a self-closing device. The same article also keeps that doorway out of a room intended for sleeping.
The practical reading: do not replace that door with a bare, unsealed interior slab, and do not remove or disable the closer because it slams. Keep the weatherstripping on all four sides and make sure the door actually closes and latches by itself. The article numbering and wording have been amended over the years and the Code was reissued in 2024, so confirm the current text with the Town's Building division if you are changing that door or its frame.
The reason is not fussiness. A garage holds a running or recently parked vehicle, fuel and solvents, and a door that hangs open or leaks air lets that into the house. If you ever sell, a missing closer or worn-out sweep on that door is also the kind of thing a home inspector writes down.
Slab or prehung: the decision that sets the job
A slab is just the door. A prehung unit comes already hung in a new frame, with the hinges and the strike side set. Neither is better in general; the right choice depends on what is wrong.
- Use a slab when the frame is straight, the old door's size and thickness match the new one, and the hinge positions are still usable. The work is trimming, marking hinge positions and boring for the lockset.
- Use a prehung unit when the frame is damaged, out of square, or the opening has changed. It costs more in material but removes the guesswork, because the door and frame are made to fit each other.
Measure three things before you shop: the width and height of the existing slab (do not trust the label on the jamb), the thickness, and the hand and swing, meaning which side the hinges are on and which way it opens. Older homes near Main Street are more likely to have non-standard sizes than the 1990s and 2000s homes in Glenway or Stonehaven-Summerhill, so measure rather than assume that a stock size will fit.
Hollow core, solid core, and why weight matters
Hollow-core doors are light and inexpensive, and they pass sound easily. Solid-core doors weigh more and block more noise, which many people want for a bedroom or home office. The extra weight is the catch: a solid-core door on two old hinges and a loose frame will sag and rub within a season. Use three hinges and long screws into the framing, not just the thin jamb, whichever type you choose.
Hardware: the part people forget to measure
A lockset needs a hole through the face of the door and another in the edge, and the two must match. Check these before you buy a new handle:
- The backset: the distance from the door's edge to the centre of the large hole. The common sizes are 2-3/8 inches and 2-3/4 inches, and most new handles will fit either.
- Passage, privacy or dummy: a closet or hallway wants a passage handle that never locks, a bathroom or bedroom wants privacy, and a pair of dummy handles suits a pantry door that only needs to be pulled.
- The strike plate: if the door now closes against a new spot, the plate has to move with it, or the latch will rattle.
Lever handles are easier to use than round knobs for children, older adults and anyone carrying a laundry basket, and they are a cheap upgrade while the door is off anyway.
Why a new door can still stick
Doors usually stick because of the frame, not the slab. Seasonal humidity swings, a settling house or a bowed jamb make the gap uneven, so a new door in the old frame inherits the old problem. Put a level on the hinge-side jamb before you buy anything. If it is out of plumb by more than a little, shimming the frame or choosing a prehung unit will fix what planing the door never will.
Where the Main Street heritage district comes in
Interior doors are a different matter from exterior ones. The Town of Newmarket's heritage permit form for the Lower Main Street South Heritage Conservation District lists alteration of doors and windows, their heads and their surrounds, among the work that may need a heritage permit. That is about what the building looks like from outside. Swapping a bedroom door inside a home in the district is not the same thing, but if the front door, a storefront door or its frame is involved, speak to the Town's heritage planner first (heritageplanning@newmarket.ca). A heritage permit does not replace a building permit, and a project can need both.
Quick answers
Do I need a permit to replace an interior door in Newmarket?
No, not if the new door fits the same opening. The Town of Newmarket says replacing a door with one the same size as the existing one does not need a building permit.
Does the door from my garage to the house have special rules?
Yes. The Ontario Building Code has long required that door to be tight-fitting, weatherstripped against exhaust fumes, and fitted with a self-closing device. Confirm the current wording with the Town's Building division before you swap it.
Can I swap interior doors in a Main Street heritage home?
Usually yes for interior doors. The Lower Main Street South heritage permit form lists alteration of doors and their surrounds, which is about the building's exterior look, but ask the Town's heritage planner if you are unsure.
Should I buy a slab or a prehung door?
A prehung door is the easier choice when the old frame is out of square or damaged. A slab is fine if the frame is sound and the hinges, size and thickness already match.
What is the most common reason a new interior door still sticks?
The frame is not plumb, so the door rubs even though it is new. Check the frame with a level before you blame the door.
The short version
Measure carefully, keep the opening the same, treat the garage-to-house door as a safety part, and look at the frame before you blame the door. That is most of the job, and it is a small enough one that getting it right once beats redoing it.
Related reading
- More home repair guides for Newmarket
- Window and Door Resealing Before Winter in Newmarket
- Garage Door Repair and Opener Replacement Cost in Newmarket
- Exterior Repairs on a Main Street Newmarket Heritage Building
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