Measuring and replacing interior doors involves taking precise measurements and carefully fitting the new door into the existing frame.
Replacing an interior door is a common home improvement project that can update the look and feel of a room. The process primarily involves accurately measuring the existing door and frame, purchasing a suitable replacement, and installing it correctly.
Step 1: Measure the Old Door Accurately
Getting precise measurements of your current door is crucial for selecting or preparing the new one, especially if you're purchasing a "blank" slab door that needs to be cut to size. Use a reliable tape measure and record your findings carefully.
Based on guidance for measuring doors, you should take the following measurements:
- Measure Horizontally (Width):
- Measure across the door in 3 locations: top, middle, and bottom.
- Why? This helps identify if the door has warped or if the frame isn't perfectly square. Use the widest measurement if there's a slight variation.
- Measure Vertically (Height):
- Measure the vertical height of the door in 3 locations: left side, center, and right side.
- Why? Like width, this checks for warping and frame squareness. Use the tallest measurement.
- Measure Thickness:
- Measure the thickness of the door itself.
- Common sizes: Most standard interior doors are 1-3/8 inches thick.
- Measure Hinge Location:
- Measure the location of all 3 hinges (or however many your door has).
- How? Measure from the top of the door to the top edge of each hinge mortise (the routed-out area where the hinge sits). Also, measure the size of the hinge mortises (height and width).
- Why? Matching hinge locations on the new door saves significant work and ensures it aligns with the existing frame.
Summary Table for Measurements:
| Measurement Type | Locations (from Reference) | Use Case |
|---|---|---|
| Width | Top, Middle, Bottom | Identify widest point, check for warping/frame |
| Height | Left, Center, Right | Identify tallest point, check for warping/frame |
| Thickness | Door edge | Match door slab thickness |
| Hinge Location | From top edge of door | Align new hinges with existing frame |
Reference: Learn more about measuring door sizes here.
You should also inspect the door frame for squareness and damage. If the frame itself is significantly out of square or damaged, simply replacing the door may not solve fitting issues.
Step 2: Select Your New Door
You have two main options:
- Pre-hung door: Comes assembled in a new frame. This is often easier but requires removing the old frame, which is a bigger job. Not typically what's meant by "replacing an interior door" in an existing frame.
- Slab door: The door panel only, without a frame or hardware cutouts. This is the standard choice when keeping the existing frame. You'll need to cut it to size, route for hinges (mortise), and bore holes for the doorknob and latch.
Choose a slab door that is slightly larger than your measured width and height. You will trim it down to the exact size. Ensure the thickness matches.
Step 3: Remove the Old Door
- Use a hammer and punch or flat-head screwdriver to tap out the pins from the hinges, starting from the bottom.
- Once pins are removed, the door can be lifted free from the frame.
- Remove the hinges and doorknob hardware from the old door.
Step 4: Prepare the New Door Slab
This is the most critical step when using a slab door:
- Trim to Size: Carefully trim the new door slab using a circular saw or table saw, referencing the measurements from your old door. Trim slightly less than needed and test the fit in the frame, progressively trimming until you have an even gap (reveal) of about 1/8 inch around the top and sides, and usually 1/2 inch at the bottom for clearance over flooring.
- Mark Hinge Locations: Place the old door directly on top of the new door, aligning the bottom and hinge side edges. Mark the exact locations of the hinges from the old door onto the new one.
- Mortise for Hinges: Use a router or chisel to create the hinge mortises on the new door slab and the frame. These must match the size and depth of your hinges so they sit flush. Using a hinge mortising jig can make this much easier and more accurate.
- Bore for Hardware: Mark the location for the doorknob and latch assembly on the new door, typically 34-36 inches from the bottom of the door. Use a door hardware installation kit (hole saw and spade bit) to drill the required holes.
Step 5: Install the New Door
- Attach the hinges to the new door slab using screws.
- Position the door in the frame, aligning the hinges on the door with the mortises on the frame.
- Insert the hinge pins to secure the door in the frame. You may need a helper to support the door during this step.
- Test the door's swing and fit. It should open and close smoothly without binding. Adjust hinge screws or slight trimming might be needed.
- Install the doorknob and latch hardware according to the manufacturer's instructions. Ensure the latch lines up with the strike plate on the door frame and adjust the plate if necessary for smooth operation.
Following these steps, especially taking accurate initial measurements as highlighted by the reference, ensures your new interior door fits and functions correctly.
