How to widen rough opening for installation of pre-hung interior door?

Question

We bought all our interior doors at 825mm width (~33.5"), which actually measure 865mm (~35.5") including the frame they're pre-hung in.

However, the drywall guy has left us with rough openings at 845–850mm width (~34.5") throughout.

The walls these doors are being hung in are all framed with metal and drywalled; none of the doorways are load-bearing.

I'm trying to figure out the best way forward here:

1. Return all the doors and buy different options – probably without the frame I guess – which fit.
2. Cut out one of the jambs, remove ~20mm of width from it, and reinstall.
3. Something else…?

#1 is a huge pain, so if possible I'd prefer to do #2 myself – or, if there's some third option I can't think of please let me know!

Here are some pics which show the door, its frame, and an example rough opening.

Answer 1

I'd just replace your trimmer studs with half-thickness boards. Easy, clean, effective. Keeps things centered. Since these aren't load-bearing there's no structural concern at all. Use a nail puller and a reciprocating saw to remove and cut nails.

Answer 2

Your plan to rip the rough framing back sounds like it might be your best bet. Of course, I'd first double check the drawings that your carpenter worked from to ensure he framed the openings to spec. If not, have him come back and do it.

In any case, I'd strongly recommend that you enlarge the opening by 30mm. If you increase it only the 20mm needed to slip the door in, you'll get stuck on any slight imperfection in your cutting, plus, if either rough jamb isn't perfectly vertical, you won't have any room at all to adjust it. By giving yourself an extra centimeter, you'll have some slack for both, and it's common and expected that you'll use shims to get the door centered in the opening and perfectly vertical/square so it operates correctly.

The other consideration is centering the door in the opening. Will it look right if the whole door is 20-30mm left or right of the center of the current opening, or do you need to take the time, effort & general pain in the butt to take 15mm off of each side so that it looks right in the end?

The example in your photo seems to be a utility closet, probably in a hallway. Nobody will notice that the door is "off center" in the hallway because it's probably not centered on anything anyway, so there's no reference. From the utility room side, it probably won't matter except for trim fit, but hey, it's a utility room, it's not supposed to look pretty and you might not even trim out the inside.

However, for bedrooms, bathrooms, etc. the look (and possibly room to fit trim) could be greatly impacted by moving the opening 3cm one way or the other. I'd suggest using some painter's tape to lay out where the door will land before cutting^*, then stand back and eyeball it just to make sure it's going to look OK. Also, you can hold your trim up against the edge (maybe even tape it to the wall) so you can stand back & look at it. You'll be most disappointed if you do all this cutting & installing only to realize that it just looks wrong by moving it one way instead of centering it on the original opening's center. Of course, the existing openings might be off a smidge and this is your chance to correct that!

^*If you do a really good job of laying out your tape nice and straight, you may want to leave the tape on while cutting. It will be an additional guide to help you to know you're cutting straight.

Answer 3

Take your opening measurements to the store where you bought the doors and tell him your problem. You may need to exchange what you have for the next size smaller door.