Prehung doors - Rough opening size

Since we purchased our home last September, I replaced the old carpet with new laminate flooring. Due to the previous owner being in a wheel chair, a number of door jambs were scuffed up (a lot). Because of this, we are replacing them.

After installing the laminate (by removing the bottom part of the old jamb), and removing the old door and jamb completely, I notice my rough opening is now approximately 81 1/2" high. The doors I purchased, unfortunately, are approximately 81 5/8" high.

What is the best way to approach this situation? Should I attempt to saw the bottoms of the jamb off (there is 1/2 inch gap between the bottom of the door and the jamb, likely for "carpet" installation) or would another tool be more suitable?

Thanks in advance :-)

 

A normal door opening is roughly 2" larger that the door, and jambs are sized accordingly. If you need to cut things for fit, then do it. The door should be about 80" from the factory, which should not need to be cut. Unless capet is thick.

 

If I understand your description, the new jambs are taller than your rough opening. You will need to cut the jambs and casings off or increase the height of the rough opening.

When I have this situation, I cut the jambs and casings. I do the cutting before disassembling the split jambs by standing the entire assembly on its edge and marking the inside of the jamb/casing "channel" with a small combination square. I then cut the casing with a jig saw. I finish the cut by cutting through the jamb with a sharp hand saw. Then the assembly is turned over to the other edge and the process repeated. Then I disassemble the split jamb and install the unit.

If you measure carefully and cut off only enough to allow the jambs to fit the rough opening, you should have enough space between the botttom of the door and the floor for the door to swing and for air circulation under the door. If this is not the case, then the bottom of the door will need to be cut off.

Good luck with your project.

 

If the new door jambs will be sitting on the laminate, you will want to check the floor very carefully with a level. Determine which side is high and which is low, then just the jambs accordingly so that the head will be level.

This is very important.

Additionally, what wirepuller mentioned- about cutting off only what you need- is true, especially if you need to cover the old paint lines on top. But you also might consider how much of a gap you want underneath the doors. While it's true that this height is "preset" by hanging an 80" door on a 81 5/8" jamb, some people do not like to see a gap under their doors that is quite large, and some people demand that gap be smaller. Something you could consider.

 

well after a few hours of trial and error, door #1 is hung. Unfortunately my first cut wasn't extremely straight, so I attempted to correct the error, then correct again, then correct again. Now I've got a door that swings open with clearance...but it sure does look tight - tighter than the 1/2" it had before, anyway. I should have started with a closet door. I did learn some valuable lessons and appreciate the tips. I guess my next question would be how in the world do you make nice straight cuts with a jigsaw?

Luckily for me my floor is very level, since I leveled it before I installed the laminate (it was in good shape before, too). The rough openings are in good shape too, without a lot of settling for a 45 year old house.

 

I don't use a jigsaw. I use a skilsaw, cutting the jamb while the door is laying on its side. The teeth of the saw blade will come up through the jamb and should not splinter the edges if you are using a nice finish blade. The only reason I could see to use a jigsaw would be if one half of the jamb was sitting on a different level of flooring, and you wanted to just notch the jamb. But a jigsaw will certainly work- a good sharp blade is the key. Homeowner type jigsaws definately don't cut as nice as the ones professionals use.