How to Install an Interior Door？

Installing an interior door is a common home improvement project that significantly impacts the look and function of your rooms. Whether you’re replacing an old door or fitting a new one, precision and the right method are key for durability and a clean finish. This detailed guide covers everything you need to know to install slab or prehung doors with confidence.

Tools and Materials You Will Need

• Door: Slab door or prehung door unit
• Hinges: Usually 3 standard hinges per door
• Door handle and latch set
• Wood shims: For leveling and adjustments
• Measuring tape and level: To ensure accurate fit and alignment
• Power drill and screwdriver bits
• Hammer and finishing nails or screws
• Chisel and mallet: For hinge mortising on slab doors
• Utility knife and pry bar: For old door removal and trimming shims
• Optional saw: For trimming door or jamb if needed

Step 1: Measure the Door Opening Accurately

Start by measuring the rough opening height, width, and depth. Measure at the top, middle, and bottom to identify any irregularities in the frame.

Pro Tip: The door slab or prehung unit should be about 1/2 inch smaller than the rough opening dimensions to allow room for shims and adjustments.

Step 2: Decide Between Slab and Prehung Door

Slab door: Just the door panel itself. Best used when the existing frame and jambs are intact and in good condition.

Prehung door: Door comes attached to its frame and is perfect for new installations or when the old frame is damaged or warped.

Step 3: Remove the Existing Door and Hardware

Carefully remove the old door by unscrewing the hinges or tapping out hinge pins. Use a pry bar to remove any trim or molding if necessary.

Save the hardware if you plan to reuse it, or discard if replacing.

Step 4: Inspect and Prepare the Door Frame

Check the door frame for rot, damage, or warping. Use a level to check if the frame is perfectly vertical (plumb) and horizontal (square).

If needed, insert wood shims behind the jambs to correct unevenness. This is critical to ensure the door hangs and operates correctly.

Step 5: Installing a Slab Door

If you’re installing a slab door, follow these detailed steps:

1. Place the door in the frame and mark hinge locations precisely.
2. Use a chisel and mallet to mortise the hinge recesses on the door edge.
3. Attach hinges to the door first, then to the frame.
4. Hang the door and check for proper swing and clearance.
5. Trim or sand door edges if the door binds or rubs the frame.

Note: Zonle slab doors are factory-machined to tight tolerances, reducing onsite fitting work.

Step 6: Installing a Prehung Door

For prehung doors:

1. Place the entire door unit into the rough opening.
2. Use a level to ensure the frame is perfectly plumb and square.
3. Insert wood shims behind hinges and latch side to stabilize and align.
4. Secure the frame by driving screws through the jamb and shims into the framing.
5. Test door swing and latch operation to confirm smooth movement.

Step 7: Install Door Hardware

Install door handle, latch, and strike plate:

• Follow the hardware manufacturer's instructions for drilling and fitting.
• Make sure the latch aligns perfectly with the strike plate to avoid sticking.
• Adjust strike plate position as needed.

Step 8: Apply Finishing Touches

Complete your installation with these final steps:

• Trim excess wood shims flush with a utility knife.
• Install door casing or molding to conceal gaps between door frame and wall.
• Paint or stain door and trim to suit your interior décor.
• Clean the work area thoroughly.

Watch Our Detailed Installation Video

Summary Table

Frequently Asked Questions

Q: How long does it take to install an interior door?

A: Installation time varies. Slab doors generally take 1-2 hours for DIYers, prehung doors may take 2-3 hours including frame adjustments.

Q: Can I reuse my old door frame?

A: Yes, if it is structurally sound and square. Otherwise, a prehung door is recommended.

Q: What if the door rubs the floor?