Replacing a bathroom door means removing the old slab or prehung unit, checking the rough opening and swing direction, then hanging the new door plumb and level with shims before installing hardware.
A door that sticks, sags, or swings the wrong way is a daily annoyance. The fix is a weekend job most homeowners can handle with a level, a drill, and a helper. This walkthrough covers the full sequence for a standard interior door, from pulling the old unit to sealing the casing, plus the compatibility checks that trip people up most.
What You Need Before You Start
Masonite’s interior-door installation guide and a Home Depot bathroom-door PDF both stress inspecting every component and verifying the space is clean, dry, and level first.
You’ll want a measuring tape, a 4-foot level, Phillips and flat-head screwdrivers, a drill with bits, a rubber mallet, shims, and finishing nails. Add gloves and eye protection. If you’re installing a bathtub or shower door instead, keep silicone sealant and an applicator on hand too.
Measure the rough opening at the top, middle, and bottom, and the height on both sides. The new door must match the opening, not the old slab. Check swing direction as well: a door that opens into the room needs its hinges on the correct side, and reversing that means flipping the entire frame.
Removing the Old Door and Frame
Masonite’s guide walks through removing the existing door and frame back to the rough opening: the side jambs, head jamb, hinge plates, and strike plates.
Drive the hinge pins up and out with a nail set and hammer, then lift the door free. Score the caulk line where the casing meets the wall with a utility knife so you don’t tear the drywall. Work a flat pry bar behind the casing and ease it off, then pry the jambs away from the framing. Pull leftover nails with a claw hammer, and vacuum the opening so the new frame seats cleanly.
| Step | What to Do | Common Mistake |
|---|---|---|
| Measure opening | Check width and height at three points | Buying a door that doesn’t match the rough opening |
| Check swing | Confirm hinge side and in/out direction | Reversed swing that forces a full frame flip |
| Center the unit | Set the prehung door in the opening | Skipping the handle-side check before fastening |
| Shim hinges | Shim behind each hinge for plumb and center | Fastening before the door hangs level |
| Pick fasteners | Use the right nail or screw for the core type | Finishing nails on a heavy solid-core door |
| Latch side | Shim so it sits even with the wall | Ignoring the vertical and level check |
| Install casing | Nail trim about 16 inches apart | Driving nails too close together and splitting trim |
Hanging the New Door Plumb and Level
Center the prehung unit, verify handle side and swing direction, then shim and fasten. Masonite specifies shimming behind each hinge so the door sits plumb and centered, then fastening at each shim location. A door hung out of square will drag for years.
Check the gap on all four sides. Slide shims behind the hinge-side jamb, top, bottom, and latch side. Check for plumb in both directions, side to side and front to back, before driving a single fastener. Get the fastener type right: Then shim the latch side so it lines up evenly with the wall and the door hangs vertically straight and level. For a picking shortcut, browse the best bathroom replacement door options before you commit to a size.
Finish with backplates, doorknobs, and strike plate per the hardware manufacturer’s instructions.
Therma-Tru’s exterior slab documentation notes that compatibility with the existing frame and sill geometry matters for a clean fit — replacement parts have to match what’s already there. Masonite’s how-to-install interior doors guide walks through the full shim and fastener sequence.
FAQs
Why does my new bathroom door keep swinging open?
The frame is likely out of plumb, or the hinges aren’t seated in their mortises. Pull the door, recheck for level in both directions with a 4-foot level, and re-shim behind the hinge locations. A quarter-inch of shim in the wrong spot is enough to make a door drift.
Can I install a slab door in an existing frame?
Sometimes, but the slab must match the frame’s height, width, and hinge layout exactly. You’ll also need to bore the latch and handle holes yourself, since slabs ship without them. Prehung units cost more but come square and predrilled.
How long before I can use a shower door after sealing it?
Let the silicone cure fully before running water near it. The Home Depot bathroom-door guide lists this as a required step, and rushing it is the fastest way to a leaky seal.
References & Sources
- Masonite. “How to Install Interior Doors.” Supports the shimming, fastener, and casing sequence.
- The Home Depot. “Bathroom Door Installation Guide.” Supports tool list, component inspection, and sealant cure notes.
- Therma-Tru. “2017 Site Manual, Section 5.” Notes frame and sill geometry compatibility for slab replacement.
