What you need to do before you start
Replacing an interior door and frame is a project most homeowners can do in a day with basic tools and some patience. The frame—the wooden box that holds the door—comes out first, then the new one goes in, and finally the door hangs on hinges. You will need a reciprocating saw or handsaw, a pry bar, a level, shims (thin wooden wedges), a drill, a stud finder, and a tape measure. The hardest part is usually removing the old frame without damaging the wall around it.
Before you buy anything, measure the rough opening—the hole in the wall where the frame sits. Measure the width at the top, middle, and bottom, and the height on both sides. If the measurements vary, write down the largest number in each direction. Take a photo of how the old door swings and where the hinges sit. If you are replacing a door that opens into a hallway or living space, you will need to account for swing clearance on the other side.
Key Takeaways
- Remove the old door first by unscrewing the hinges, then pry out the frame carefully to avoid damaging the wall studs and drywall around it.
- Measure the rough opening at three points in each direction because walls are rarely perfectly square, and order a frame that fits the largest measurement.
- Set the new frame level and plumb using shims and a level before fastening it to the studs, because a crooked frame will cause the door to swing shut or stick.
- Hang the door on the hinges, then adjust it so it closes smoothly with even gaps on all sides, which usually requires moving shims slightly and re-tightening fasteners.
Removing the old door and frame
Start by taking the door off its hinges. Open the door fully and look at the hinges—usually three of them, one near the top, one near the bottom, and one in the middle. Tap a nail or punch up from underneath each hinge pin to pop it out, then catch it as it rises and pull it free. Lift the door away and set it aside. If the hinges are painted shut, spray them with penetrating oil and wait 15 minutes before trying again.
Next, remove the trim (also called casing) around the frame on both sides of the wall. Use a pry bar to gently lift the trim away from the frame, working from the middle outward so you do not split the wood. Once the trim is off, you can see the frame itself. Look for nails or screws fastening the frame to the wall studs on both sides. Remove these fasteners—if they are nailed, pry them out; if screwed, unscrew them. Then pry the frame out of the opening, starting at the top and working down. Go slowly and check that you are not pulling the drywall with it.
Preparing the rough opening
Once the old frame is out, inspect the studs and drywall around the opening. If the drywall is damaged, patch it with drywall compound and sand it smooth before the new frame goes in. Check that the studs are straight by laying a level against them. If a stud is bowed inward or outward, you may need to shim it out or plane it down slightly so the frame sits flush.
Measure the rough opening one more time to confirm your measurements. The new frame should fit snugly but not so tight that you cannot tap it into place. If the opening is wider than expected, you may need to add a shim or thin piece of wood to one side. If it is narrower, you will need a smaller frame or a frame that can be cut down—check with the supplier before ordering.
Installing the new frame
Set the new frame into the opening and check it with a level. The frame should be plumb (perfectly vertical) on both sides and level (perfectly horizontal) across the top. Start by placing shims behind the frame on one side at the top hinge location, then check plumb. Adjust the shims until the frame is perfectly vertical, then fasten that side to the stud with two screws or nails. Do not fully tighten yet—just snug enough to hold it in place.
Move to the other side and repeat the process: place shims, check plumb, and fasten loosely. Then check the top of the frame with a level and adjust shims as needed to make it level. Once the top is level and both sides are plumb, place shims at the middle and bottom of each side, check again, and fasten all points securely. Use at least two fasteners per side, spaced evenly. Trim the shims flush with the frame using a handsaw or utility knife.
Hanging the door
Before you hang the door, check that the frame opening is square by measuring diagonally from corner to corner. Both diagonal measurements should be the same; if they differ by more than a quarter inch, loosen the fasteners and adjust the shims until the frame is square. Once the frame is correct, you can hang the door.
Position the door in the frame and insert the hinge pins one at a time, starting at the top. The door should swing freely and close without binding. If it sticks or swings open on its own, the frame may not be plumb—check with a level and adjust shims if needed. Once the door closes smoothly, check the gaps: there should be about an eighth of an inch between the door and frame on all sides. If the gap is uneven, loosen the hinge screws slightly, tap the door into position, and re-tighten.
Sealing and finishing
Once the door hangs correctly, seal the gap between the frame and the wall studs with expanding foam or caulk. Spray foam expands as it dries and fills irregular gaps; caulk works for smaller, more uniform gaps. Let the foam cure fully (usually 24 hours) before trimming it flush with a utility knife. Do not over-fill—excess foam can push the frame out of plumb.
After the sealant is dry, install new trim around the frame on both sides of the wall. Measure and cut the trim to fit, then nail or screw it to the frame and studs. Fill nail holes with wood filler, sand smooth, and paint or stain to match your walls. The door is now ready to use.
When to call a professional
If the rough opening is badly out of square—diagonal measurements differ by more than half an inch—or if the studs are severely bowed or damaged, a carpenter should assess the wall before you proceed. If you discover rot in the studs or drywall, that area needs to be repaired or replaced before a new frame can be installed properly. If the door binds no matter how you adjust the shims, the frame may be warped, and the supplier should replace it under warranty.
If you are not comfortable using a reciprocating saw to remove the old frame, or if the frame is painted heavily and you cannot locate the fasteners, a handyman or carpenter can remove it quickly and safely. The installation itself is straightforward enough for most homeowners, but the removal is where mistakes happen.
Frequently Asked Questions
Can I reuse the old hinges on the new door?
Only if the old hinges are in good condition and the new door is the same size and thickness as the old one. If the old hinges are loose, rusted, or bent, buy new ones. New hinges are inexpensive and will may support the door hangs smoothly.
What if the new frame does not fit the rough opening?
Measure again to confirm. If the opening is slightly too wide, shim one side. If it is too narrow, you may need to remove a small amount of drywall or wood from the studs, or order a frame that is a half inch smaller. Contact the supplier before cutting anything.
How do I know if the frame is level and plumb?
Use a two-foot or four-foot level. Place it vertically against each side of the frame to check plumb, and horizontally across the top to check level. The bubble should be centered in the vial. If it is not, adjust the shims until it is.
Do I need to remove the trim before taking out the old frame?
Yes. The trim covers the fasteners that hold the frame to the studs. You cannot remove the frame without removing the trim first. Save the trim if it is in good condition and you want to reuse it.
What is the difference between a prehung door and a slab door?
A prehung door comes already hung on hinges in a frame, ready to set in the opening. A slab door is just the door panel without hinges or frame. For a frame replacement, you need a prehung door or a frame and separate door. Prehung doors are easier because the hinges are already aligned.