How to Build an Interior Slab Door

Need a Custom Size for an Interior Door? Build it Yourself!

I live in a manufactured home where the doors are not a standard height. When I needed a new door for the bathroom (because I used the old one to make a fabulous top for a desk), I knew I could easily build one myself that would fit the doorway perfectly! Today, I will share how to build an interior slab door that is inexpensive and easy to make!

Doors are either 1-3/8″ thick (generally interior) or 1-3/4″ thick (generally exterior). The door I wanted to build had to be 1-3/8″ thick. I used 5mm underlayment for the front and back which is slightly less than 1/4″ thick. I added scrap strips of the underlayment to the 1×6 frame of the door in order to give the door the thickness I needed.

Narrower boards can be used to build the inner frame which will help reduce the weight (see notes in the design drawings for constructing the door using 1x3s). The only thing I was afraid of was the pocket holes interfering with cutting the hole for the door knob (they didn’t!). The door frame can also be constructed using 1/2″ plywood (two frames built, then secured together to make it 1″ thick and used with 5mm underlayment) or 5/4 boards (which are usually 1″ thick and used with 5mm underlayment).

I used 2″ edge banding on the sides of the door but not the top and bottom – no one will see it!

Materials:

• 1-1/4″ pocket hole screws (<– affiliate link!)
• 3/4″ brad nails (<– affiliate link!)
• Wood glue
• 2″ edge banding, optional (<– affiliate link!)
• Sandpaper (I used 150 grit)
• Finishing supplies such as primer and paint, or stain and sealer

Lumber:

• 3 – 1×6 at 8′
• 2 – 4′ x 8′ sheets of 1/4″ (or 5mm) plywood or underlayment

Cut List:

• 2 – 1×6 at the finished height of the door
• 3 – 1×6 at the finished width of the door minus the width of the side 1x6s
• 2 – 1/4″ (or 5mm) underlayment at the finished size of the door**

** If using 5mm underlayment, spacers will need to be cut from the scrap and laminated to the 1×6 frame in order to make the door thickness 1-3/8″.

Step One

Measure the door opening in three places – for the width, measure the top, middle and bottom, and for the height, measure the left side, middle and right side. For the height, pick the smallest of these measurements and subtract approximately 3/4″ to allow for space at the top and bottom of the door. For the width, pick the smallest measurement and subtract approximately 1/2″ to allow for space at the sides. These measurements will be the finished dimensions of the door.

Step Two

Cut the pieces for the 1×6 frame. Cut two pieces at the finished height of the door. Cut three pieces at the finished width of the door minus 11″ (the width of the two 1×6 side pieces).

Set the pocket hole jig for 3/4″ material, and drill pocket holes in each end of the shorter pieces. Assemble the frame using glue and 1-1/4″ pocket hole screws.

Step Three

If using spacers, secure the spacers to the frame using glue and 3/4″ brad nails, with the outside edges flush with the frame.

Cut the pieces for the front and back panels. Spread glue on the frame (generously), then secure each panel in place with 3/4″ brad nails. Clamp the panels in place, if necessary.

Apply the edge banding to the sides of the door, then trim as necessary.

Finish the door as desired, then hang in the opening using 3″ hinges (I used non-mortise hinges). Cut the opening for the lockset (a door knob jig is great for this!), then install the lockset.

That’s it… Super-easy, right? The best thing about building your own door is that it can be finished or customized any way you like…

Have any questions about how to build an interior slab door? Leave a comment below!