Doors and Windows - Split casing installation....

Good morning,

Looking for some help on installing a "prehung" door. These are solid wood 6 panel doors with a split casing/jamb. I'd not run across these before, but basically the door jamb is split vertically at the door stop. Each side already has the casing installed and mitered, with one side having the hinges, and the other just the casing and the rest of the jamb. The two key together and form the casing. It also allows for a little wall thickness variation this way.

Trouble is, I'm not sure how to mount the jamb. I installed one by removing the door, and I shimmed the hinge side of the one jamb straight up and down, and then made sure the top jamb was level. I then put the door back on and checked the fit of the latch side. The striker opening and the pre-drilled latch opening are off by about 1/4" as if the door sagged. Could there be that much slop in the hinges? Should I shim the hinge side slightly non-vertical so the door hangs level when installed?

I think I can fix the one I've already done, but don't want to do any more until I figure out what I did wrong. In the past, I just made sure the jamb was plumb and level, and that the spacing was even, and the door would then fit great. But, those were always luan hollow doors before.

Any ideas? This is the first time I'd ever seen this door jamb style - slick (if I could hang it right!)

Thanks, Glen

You said that the head of the jamb is level, but when the door is closed, what does the reveal look like on the top? Is there a 1/8" gap all the way across? Or does the reveal get wider on the latch side? If this is the case, the easiest fix is to stick a shim under the bottom leg of the jamb on the hinge side. Assuming your door is plumb, that is. Taking out one of the screws in the top hinge and replacing it with a longer screw that goes back into the jack stud may also help pull up a sagging door. Solid core doors often sag unless you put some nice shims behind each hinge and then put 1 long screw in each hinge. (especially the top and middle hinges)

I've also run across quite a few prehung doors where they have routered the strike plate and hinge mortises too low.

Although I have not hung any split-jamb pre-hung units, I would imagine it would be pretty much like a fixed width jamb with the casing left off the side opposite the hinges.

The first thing I do in hanging a pre-hung door is to place a 2x4 next to each side and make a mark on the floor. Next, I place the 2x4 (needs to be straight) across the opening on the floor. Using a speed-square, I mark a line perpendicular to the 2x4 at each mark. This gives me a reference line to 1) center the unit in the opening and 2) make sure the jambs are perpendicular to the plane of the wall. Leaving the door installed, place the unit in the opening. Depending on the thickness of the finish floor, I place a 1/4" to 1/2" shim under the hinge side jamb. I use a 6' level placed vertically against the hinges to plumb the door (in the wall plane) and nail through the casing on the hinge side. Monitor the gap between the top of the door and the jamb and nail the top casing (I don't think it is necessary to check for level - a consistent gap is more important. If the hinge side is plumb, the top will be level.) Continue nailing from the top of the strike side down as you adjust the gap between the door and jamb. Then, shim the jamb, 1) making sure that the jamb is parallel to the line drawn on the floor and 2) the door is plumb in the plane perpendicular to the wall. Nail through the jambs. Then, install the casing on the other side, or in your case the other half of the jamb and casing. If the door is plumb (in both planes) and the gap around the door is consistent and the striker opening and the pre-drilled latch opening are off, then the manufacturer's jig was off. Some suppliers nail through the jamb (on the latch side) into the door to hold the unit together for shipping and handling. Be sure to remove these before placing the unit in the opening.

Thanks for the responses. I believe I've got them installed properly, and the "sag" or droop is not as bad as I originally thought. From what I can tell, it is coming from three places - 1) I didn't get everything perfectly level, and 2) the mortises are slightly off, and 3) the hinges (made in China - oh boy!) have more slop in them than I've seen before.

None are so bad that I can't slightly adjust the latch plate. Still disheartening, though, to go to all the work and expense, and have a door that doesn't fit perfectly.....

Thanks again...Glen