How to Install an Interior Door？

Installing an interior door correctly is not just about appearance — it directly affects sound insulation, durability, smooth operation, and long-term stability. Whether you are replacing an old door or installing a new one during renovation, this guide walks you through the industry-standard installation process used by professional door manufacturers and installers.

This article is written based on factory-level production standards and international installation practices, making it reliable for homeowners, contractors, and B2B buyers alike.

Why Proper Interior Door Installation Matters

A poorly installed interior door can cause:

• Door sagging or rubbing on the floor

• Gaps leading to poor soundproofing

• Lock misalignment and premature hardware failure

• Reduced door lifespan

Professional installation ensures:

• Accurate alignment and smooth opening/closing

• Better acoustic performance

• Long-term structural stability

• Compliance with international building standards

Tools and Materials You Will Need

Before starting, prepare the following tools used by professional installers:

• Measuring tape

• Spirit level

• Hammer or nail gun

• Power drill

• Wood shims

• Screws and finishing nails

• Door frame (pre-hung or slab)

• Hinges and door handle set

• Expanding foam or wood filler

• Safety gloves and goggles

Step 1: Measure the Door Opening Accurately

Accurate measurement is critical.

Measure:

• Width (top, middle, bottom)

• Height (left and right)

• Wall thickness

Industry Tip:
The rough opening should be 20–25 mm wider and higher than the door frame to allow proper adjustment using shims.

Step 2: Choose the Right Type of Interior Door

Interior doors come in two main types:

Pre-Hung Interior Door

• Door already mounted in the frame

• Faster installation

• Recommended for beginners and large projects

Slab Door

• Door panel only

• Requires precise hinge and lock placement

• Preferred by professional installers for custom projects

Step 3: Install and Level the Door Frame

1. Place the frame into the opening.

2. Insert wood shims at hinge points and top corners.

3. Use a spirit level to ensure the frame is perfectly vertical and horizontal.

4. Secure the frame with screws, starting from the hinge side.

Professional Standard:
Always fix the hinge side first — this determines door alignment and load-bearing accuracy.

Step 4: Mount the Door and Check Alignment

If using a pre-hung door, this step is partially completed.

For slab doors:

1. Mark hinge positions according to factory specifications.

2. Secure hinges firmly to both door and frame.

3. Hang the door and test movement.

The door should:

• Open and close smoothly

• Have consistent gaps (2–3 mm) around edges

• Not touch the floor or frame

Step 5: Install Door Hardware

Install:

• Door handle and latch

• Strike plate

• Optional lock or privacy hardware

Quality Check:
The latch should engage smoothly without forcing. Misalignment here indicates frame or hinge issues.

Step 6: Secure, Seal, and Finish

1. Fill gaps between frame and wall using expanding foam or wood filler.

2. Cut excess foam after curing.

3. Install architraves or trim.

4. Touch up with paint or finish.

This step improves:

• Sound insulation

• Visual finish

• Structural stability

Common Interior Door Installation Mistakes to Avoid

• Skipping leveling checks

• Over-tightening screws (causes frame distortion)

• Ignoring wall unevenness

• Using low-quality hinges or hardware

• Not allowing expansion gaps

Professional Recommendation

For projects involving custom wooden doors, WPC doors, soundproof doors, or fire-rated interior doors, professional installation is strongly recommended to ensure compliance with international quality and safety standards.

Manufacturers often provide installation specifications that should always be followed to maintain warranty and performance.

FAQs About Installing Interior Doors

Can I install an interior door myself?

Yes, basic installations are DIY-friendly, but precision is required. Pre-hung doors are easier for non-professionals.

How long does it take to install an interior door?

Typically 1–2 hours for a pre-hung door and 2–4 hours for a slab door.

Should interior doors touch the floor?

No. A clearance of 8–12 mm is recommended for airflow and floor movement.

Do interior doors need insulation?

While not mandatory, sealing gaps improves soundproofing and overall comfort.

Final Thoughts

Installing an interior door correctly is a combination of accurate measurement, proper alignment, and professional-grade materials. Following these steps ensures long-lasting performance and a high-quality finish.

For large-scale projects or custom interior doors, working with an experienced door manufacturer or supplier guarantees both product quality and installation reliability.