Interior doors are one of the easier trim jobs and can be done using a split jamb door. A split jamb door is exactly that-a door that splits apart at the jamb. The outer trim separates from the door inner trim and the hinges. Installing an interior door slab is also not very difficult and can be done by just about anyone with a hammer.
An interior door must be hung on a stud wall opening 4 Â½” thickness opening. 2×6 opening are available as well as a 2×8 opening but of course they are special orders and cost more, sometimes taking months to backorder from the door factory. Typically the drywall is finished and painted.
Begin by splitting the new door open. Remove any cardboard or plastic wrapping from the door. Remove the plastic screw door lock and discard. Check for any screws or staples holding the door jambs together on each side and top of the jamb. Remove staples carefully while the door is supported against a set of sturdy sawhorses.
Carefully split the jamb apart and set the frame part aside. Grab the door and frame carefully and set into the rough opening with the proper swing facing your back. Press the trim flush against the drywall.
Tack a finish nail into the upper hinged corner of the trim. Using a torpedo level, check the door both vertically and horizontally for plumb. Adjust as needed using wood shims. Set another 10d finish nail into the lower corner.
Now close the door and adjust the unhinged trim side until the correct reveal is achieved around the entire door. Wood shims can help you hold the trim and door in place as you set two more finish nails in either corner. Check the door for working order and a symmetric reveal around the entire door. Now you can add additional finish nails and set them.
Repeat the same process fro the other side of the split jamb door. Although you can’t use shims, you probably won’t need to adjust it much. The jamb will fit tightly into the opposite jamb slot. Make sure the trim is pressed firmly against the drywall and set the finish nails. Fill with wood putty and your interior door is complete