Replacing an interior door is one of the most satisfying DIY upgrades an Ontario homeowner can do. A new door immediately improves the look of a room, reduces noise transfer, and fixes that annoying sticking, rattling, or swinging problem the old door had. With a pre-hung unit and basic tools, most GTA homeowners can complete a door installation in two to four hours — no permit required for a straight door replacement.
This guide covers the full process: choosing the right door unit, removing the old door and frame, setting and shimming the pre-hung unit, fastening to studs, and finishing with casing trim and hardware. For context on what a full bathroom or kitchen renovation costs when trades are involved, see our bathroom renovation cost guide for Ontario and kitchen renovation cost guide for the GTA.
Pre-Hung vs. Slab: Which Door Do You Need?
This is the first decision — and getting it wrong costs time and money. A pre-hung door comes as a complete unit: door panel, hinges, and the full frame (hinge-side jamb, latch-side jamb, head jamb, and door stop). It is the right choice when you are replacing both the door and the existing frame, which is true in almost all renovation scenarios. A slab door is the door panel only, with no frame. Use a slab only if your existing frame is perfectly square, plumb, and undamaged and you simply need a new door panel to hang in it.
💡 When In Doubt, Buy Pre-Hung
A pre-hung 32"x80" hollow-core door at Home Depot or RONA costs $100–$180 CAD in 2026. A slab-only door costs $60–$130. The $40–$50 difference is far less than the cost of trying to true up a warped or damaged existing frame. If the old frame has any play, twist, or rot, pre-hung is the right call every time.
2026 GTA Interior Door Pricing
| Item | 2026 GTA Price (CAD) | Where to Buy |
|---|---|---|
| Pre-hung hollow-core door (32"x80") | $100–$180 | Home Depot, RONA |
| Pre-hung solid-core door (32"x80") | $200–$450 | Home Depot, RONA, specialty millwork |
| Barn door hardware kit | $150–$400 | Home Depot, RONA, Amazon |
| Door handle / knob set | $40–$120 | Home Depot, RONA |
| Hinge kit (3-pack) | $15–$30 | Home Depot, RONA |
| Shims (bundle) | $5 | Home Depot, RONA, any hardware store |
| Pro door installation | $200–$350 per door | Local carpenter / renovation contractor |
Tools You'll Need
🔧 Required Tools
- Pry bar and hammer
- Utility knife
- Level (4-foot preferred)
- Tape measure
- Drill / driver with 3-inch screws
- Hand saw or oscillating tool (for shims)
- Nail gun or finish nails + hammer (for casing)
📦 Materials
- Pre-hung interior door unit
- Cedar shims (2 bundles)
- 3-inch structural screws (for frame-to-stud)
- 2-inch finish nails (for casing)
- Door handle / lockset
- Wood filler and paintable caulk
- Paint to match existing trim
Step-by-Step Interior Door Installation
Remove the Old Door and Frame
Start by removing the casing trim on both sides of the door — score along the paint line with a utility knife first to avoid tearing the drywall paper. Use a pry bar to work the casing off carefully. Next, remove the door from the hinges (tap out the hinge pins with a nail and hammer). Finally, pry the old jambs away from the rough opening. Work slowly on the hinge-side jamb — it is typically nailed directly into the king stud and removing it aggressively can damage the drywall. If the drywall is torn, patch it now before continuing.
Check and Prepare the Rough Opening
With the old frame out, measure the rough opening: width at top, middle, and bottom; height on both sides. For a standard 32"x80" door, the rough opening should be approximately 34 inches wide and 82.5 inches tall. If your opening is close but slightly off, minor discrepancies (up to 1/2 inch) can be managed with shims. Check whether the floor is level across the opening with your level — an unlevel floor means you'll need to shim differently on each side. Vacuum out any debris and check that the king studs are solid and accessible for screwing.
Set the Pre-Hung Unit in the Opening
Lift the pre-hung unit into the rough opening. For a 32-inch door, this is manageable solo — have a second pair of hands nearby for larger doors or solid-core units (which are significantly heavier, often 50–80 lbs). Center the unit in the opening and let it rest on the floor. If the floor is unlevel, slip shims under the low-side jamb at the floor so the unit sits level across the threshold. Open and close the door once — it should swing freely without dragging on the floor.
Shim and Plumb the Hinge-Side Jamb First
Always start with the hinge-side jamb — getting this side perfectly plumb is the most critical part of the installation. Hold your level against the hinge-side jamb. Insert shims in pairs (one from each side, opposing each other) at the top hinge location, middle hinge location, and bottom hinge location. Tap shims in until the jamb reads perfectly plumb on your level. The gap between the jamb and the rough opening framing should be consistent (about 3/4 inch on each side for the jamb thickness plus shims). Once the hinge side is plumb, drive a single 3-inch screw through the jamb at each shim location — just snug, not fully tight yet.
Shim and Fasten the Latch-Side Jamb
Close the door and check the gap between the door panel and the latch-side jamb — it should be consistent (about 3mm / 1/8 inch) from top to bottom. Insert shims behind the latch-side jamb at the top, middle, and strike plate location to achieve a consistent gap. Plumb the latch-side jamb with your level, then drive 3-inch screws through the jamb at each shim location into the king stud. Check the head jamb across the top — it should be level and show a consistent gap at the top of the door. Open and close the door several times. It should swing smoothly and the latch should engage the strike plate cleanly. If it binds or sticks, adjust shims before fully tightening all screws.
⚠️ Screw Into Studs — Not Drywall
Every screw fastening the door frame must go through the jamb, through the shim, and into the king stud. Screwing only into drywall will result in a frame that shifts over time, causing the door to stick or swing open on its own. Use a stud finder or knock on the wall to confirm stud location — king studs run vertically along both sides of the rough opening and are always present.
Trim the Shims Flush
Once all screws are tight and the door operates correctly, score the protruding shims with a utility knife and snap them flush with the face of the jamb. Alternatively, use an oscillating tool or hand saw to cut them flush. Do not leave protruding shims — they will prevent the casing trim from sitting flat against the jamb.
Install Casing Trim and Hardware
The casing trim covers the gap between the jamb and the surrounding drywall on both sides. Cut casing at 45-degree mitre joints at the top corners. Nail casing to the jamb with 2-inch finish nails and to the wall stud or drywall with 2.5-inch finish nails. Set the nail heads with a nail set, fill with wood filler, and caulk the seam between casing and wall. Paint to match. Install the door handle set per the manufacturer's instructions — most pre-hung doors come with a pre-bored latch hole. Install the strike plate on the latch-side jamb, testing the latch engagement. Finally, install the door stop on the wall side to prevent the knob from punching through drywall.
When to Call a Pro
Interior door replacement is well within DIY range for most GTA homeowners. Call a carpenter when: the rough opening needs to be re-framed or enlarged; the existing wall shows structural damage or rot; you are installing a pocket door or barn door (which require different framing and hardware); or the floor is dramatically out of level requiring extensive shimming and scribing. Professional door installation in the GTA runs $200–$350 per door including labour but not the door unit itself.
Frequently Asked Questions: Interior Door Installation
❓ Pre-hung vs slab — which do I need?
Pre-hung when you are replacing both the door and the existing frame — the right choice in most renovation scenarios. Slab-only if your existing frame is perfectly square, plumb, and undamaged. In practice, most Ontario homeowners doing a full door replacement should buy pre-hung. The extra cost ($40–$50) is far less than the labour of fixing or working around a warped frame.
❓ How do I tell if my rough opening is the right size?
For a standard 32"x80" door, rough opening should be approximately 34" wide x 82.5" tall — 2" wider and 2.5" taller than the door. Measure at top, middle, and bottom. Minor discrepancies up to about 1/2 inch can be handled with shims. If the opening is significantly undersized, framing work is needed before the door goes in.
❓ Can I install a door without hitting studs?
No. Every fastening screw must penetrate the king stud on each side of the rough opening. Screwing into drywall only will produce a frame that shifts, sticks, and eventually fails. King studs run vertically along the sides of every door rough opening — use a stud finder to confirm location before driving screws.
❓ How do I fix a door that sticks after installation?
Sticking almost always means the frame is not perfectly plumb. Check the gap around all four door edges — it should be uniform (about 3mm). If uneven, loosen the hinge-side screws, re-adjust the shims until the gap is consistent and the door swings freely, then retighten. Address frame alignment before reaching for a plane.
❓ Can I replace a door without replacing the frame?
Yes — if the existing frame is square, plumb, and undamaged. Buy a slab door with matching hinge cutouts, rehang on existing hinges, and adjust the strike plate. This is most reliable in older GTA homes where the original framing is still true. If there is any warping or rot in the existing frame, replacing the entire pre-hung unit is the better call.