A prehung interior door is a great way to enhance your home’s appearance and functionality. Since the door comes attached to its frame, installation is more manageable for DIY enthusiasts. To install a prehung interior door, check the rough opening, position the door, ensure its level and plumb, secure the frame with shims and screws, and attach the trim and hardware.
This guide will provide you with clear, step-by-step instructions for a successful installation. Doing the job correctly will improve the door’s look and ensure smooth operation and better efficiency.
| Project difficulty: Intermediate Estimated time to complete: 3 to 4 hours Project cost: $348 |
Supplies Needed
Materials Needed
- Prehung interior door
- Shims
- Screws
- Trim
- Wood filler or caulk
- Locks
Tools Needed
- Drill
- Leveling tool
- Reciprocating saw
- Utility knife
- Tape measure
- Circular saw
- Nail gun
- Miter saw
- Rad nailer or finish nailer
- Chisel
Steps to Install a Prehung Interior Door
Step 1: Remove the Old Door
To install your new prehung door, detach the old door from its hinges. Use a screwdriver or drill to remove the hinge pins and lift the door off carefully. Next, score along the edges of the trim with a utility knife to prevent wall damage, then gently pry off the trim or molding.
Use a reciprocating saw to cut through any nails or screws securing the door frame. After you remove the frame, clear the opening of debris, nails, or any other obstacles to create a clean space for the new door. Take your time to avoid damaging the surrounding wall or floor. If you are working with a brand-new opening, you can skip this step and move on to the next installation phase.
Related: How to Take a Door off Its Hinges
Step 2: Check the Rough Opening
To ensure proper door installation, you must position the door so it is plumb and level within the rough opening. Start by checking the floor’s level using a leveling tool. If you find the floor uneven, adjust the tool to determine how much you need to correct during installation.
Next, establish a reference line across the wall inside the rough opening. Position a 4-foot level and ensure it’s perfectly balanced. Then, draw a straight line on both sides of the wall. This line will act as your guide for precise measurements.
On the hinge side of the rough opening, measure from the floor up to the reference line and record the measurement. Then, repeat the process on the striker side. The difference between these two measurements indicates how much the floor is out of level.
Step 3: Adjust the Jamb Height If Needed
To properly fit the door, transfer the reference line to the jamb of the new door. Then, adjust the jamb height based on the two sides’ differences. To do this, first, hook your tape measure at the bottom of the door and measure up to the original reference line you marked earlier. Allow for a 7/16-inch gap to accommodate the tile.
Next, check that the header, the horizontal frame piece at the top of the door opening, is level. On the hinge side, measure from the top to the reference line on the new door. Repeat this step on the striker side and mark the same point.
Finally, hook your tape measure to the bottom of the jamb and measure the height on both the hinge and striker sides. The difference between these measurements shows how much you need to trim. The side you cut will depend on the floor’s level, which you checked earlier. Use a circular saw to cut.
Dealing With a Wide Rough Opening
What if the rough opening is too wide for the available pre-hung door? Quora user Craig Lenhard, a handyman, carpenter, and furniture maker, shares his approach to fixing this issue.
He explained that the rough opening should be no more than an inch wider than the door jamb. If the gap is wider, you can fill the extra space by attaching a ¾-inch by 3½-inch board to the frame.
Then, use wood shims to square up the door and nail through the shims to secure it. For larger gaps, consider adding a 2×4 to the frame or replacing the door with one that better fits the opening.
Step 4: Check and Prepare the Frame
The next step is to check whether the rough frame is plumb. Place the level at the bottom of the door frame, resting it against one side, and hold it steady with your foot. Slowly move the level upward along the frame to check for alignment. If the frame is not plumb, tilt the top of the level slightly away from the frame to identify the gap.
To correct the issue, insert a couple of shims near the top hinge area to adjust the frame until it becomes plumb. Hold the shims in place, then remove the level and secure the shims with a few tacks using a nail gun.
Step 5: Install the New Door
Start by sliding the door into the rough opening and position the jamb so it aligns flush with the wall. Fully open the door and have an assistant help hold it in place. Check that the edge of the door jamb aligns with the wall’s surface and that the reference line on the wall matches the jamb of the new door.
Press the jamb tightly against the top shims, hold the door steady, and drill a pilot hole near the hinge. Insert a screw to secure it. Afterward, verify that the jamb stands plumb. If you have aligned everything correctly, secure the screws on the sides of the remaining hinges.
On the striker side, confirm that the reference line on the new door aligns with the one on the rough opening wall to keep the header even. Place shims at the bottom of the jamb until the lines match.
Close the door to ensure proper fit, then temporarily secure the top with a screw. Shim the door down to create even spacing along the bottom. Finally, fasten the jamb to the shims to secure the door in place.
Read more: How to Hang a Door
Step 6: Install the Door Trim
After securing the door, the next step is to install the trim. For a traditional look, cut the ends of the top trim piece at 45-degree angles so they align with the side trim pieces. Use a miter saw for accuracy.
If you prefer a simpler, more modern style, you can make straight (square cuts) and butt the side pieces directly against the top trim.
Position the top piece of trim flush against the door jamb and wall, ensuring it sits evenly. Secure it with a finish or brad nailer, placing nails every 12 inches. Repeat the process for the side trim pieces, making sure the mitered or square cuts fit snugly. Once the trim is attached, fill any gaps or nail holes with wood filler or caulk for a seamless finish.
Step 7: Attach the Hardware and Accessories
Once you position the door, the next step is to attach the necessary hardware, such as the strike plate, doorknob, and latch. Start by securing the strike plate to the latch jamb using the provided screws. If the plate is too large for the mortise, outline it with a pencil and adjust the opening with a chisel.
Next, insert the latch bolt into its designated hole and secure the latch plate to the door edge with screws. If you find the hole too tight, make adjustments as you did for the strike plate.
Install the doorknobs on both sides of the door and tighten the connecting screws. Afterward, close the door and check that the latch slides into the strike plate smoothly. Finally, tighten all screws to attach the hardware securely.
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Read more articles:
- How to Hang a Prehung Exterior Door
- How to Hang an Exterior Door in an Existing Frame
- How to Hang an Interior Door in an Existing Frame
Main Photo Credit: Mountains Hunter / Adobe Stock Free / License
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