How a Split-jamb Door Works
Q: How does a split-jamb door work?
A: Prehung split-jamb doors are designed for situations where an interior wall’s rough frame is thicker than a standard opening, and a standard size prehung jamb won’t fit. Split-jamb doors have a two-piece jamb that is separated lengthwise and sandwiches the wall between the two pieces. When installing, set the unhinged side in the room with the hinge-stop side in the opening track. The casing is already attached to split-jamb doors, so tack a nail through the casing near the top. Shim the door as necessary to keep it plumb and square, and nail through the jamb, securing it to the door frame with finishing nails. Install the other slip of the door on the opposite side of the wall, pushing it into position until the casing reaches the wall. Nail through both halves of the jamb into the center stop. Nail the casing to the wall and fill all nails holes with putty.