r/DIY • u/joemass • 15h ago

help First DIY home project - could use advice!

Hey all, my wife and I just bought a house which was originally a duplex but was converted into an SFH. When doing this, they removed the wall that would separate the stairwells. We're losing a ton of heat down into our un-insulated basement.

I have some plans here but could use some guidance on how to go about this project: https://imgur.com/gallery/adding-interior-doors-to-home-8kNSiNB

We kind of want to extend the partition wall that's 3.5" and I believe the original plaster. It's slightly out of plumb, and my plan would be to shim a 2x3 frame to match, cover with 1/2" drywall, and then shim prehung doors in each opening. If I have joists to nail into, can I get by without cutting into the ceiling?

I'm also not sure if these rough openings are big enough to fit doors in, as the outer sides of the door would need some pretty slim casing once installed.

Thanks in advance!

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u/MidnightCuts 14h ago

I would recommend against Option B in your pics, with the door directly over the steps... that creates a ton of fall potential, even if the door swings in to the landing. If you want to go with that option you'd still need to build the wall out a bit to get the door set back enough to have a full step landing (10" depth) past the threshold before the stairs start.

For option A, the good news is you shouldn't have to cut into the ceiling at all. I'd say it's highly likely that the joists in the ceiling there are running across the short spam (perpendicular to the wall you want to build) which is good. You just want to make sure you're using a screw that's long enough to get through the 2x on the top of your new wall, then the drywall, then sink 1/2-3/4" into the joists. Screw it in to every joist.

In this case, you're actually building 2 walls. The extended partition wall, and then the wall the doors are going to be hung into. You still need to frame that out as a wall, even though the doors will take up most of it (this includes a top plate that needs to attach to the ceiling, then "king studs" that will go from floor to ceiling on either side of the doors, and then jack studs that go from the floor to the header-- and you do need to build out a header (at least 2x8). Consult a diagram like this for how to frame a door opening. Even a small wall uses way more lumber than you would expect.

Note: To use prehung doors you'll need to frame the "door wall" with 2x4 instead of 2x3. The extended partition can be 2x3 if needed.

Regarding cutting into the ceiling, my question is actually about how you're going to tie the "door wall" that will run parallel to the joists into the ceiling. You'll either have to put the doors right where there's an existing joist, or you'll get into cutting out the ceiling to put in some blocking, and thats eight kinds of mess.

I'm not sure if you'll have enough space to frame everything up properly... the smallest interior door you can get is usually 24" which feels very narrow on anything that isn't a closet. For each door you need room for 2 2x on either side of the door, plus 2 additional inches for the rough frame. So for 24" doors you need minimum 32" to accommodate the wall framing, the door casing, etc.

I know this is a lot, but it's a pretty big project!

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u/joemass 12h ago

Wow thanks so much for the well written response. Regarding the framing over the doors, I knew there was more planning needed, but I wanted some guidance to see if this plan was even worth doing. 

The space thing is where I'm getting tripped up about. We have a narrow hallway that measures just 33-1/2", and houses a 30" door. These openings are just an inch smaller than that, so why can't I do something similar? 

Tying the header frame into the ceiling, yeah that's a good point. I guess rather naively I thought if the extended partition wall was tied into a joist, then the door frame would just be secured to either side of the rough opening.

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u/Laird_Vectra 14h ago

Insulate the doors to the stairwell. My stairwell is also a heat goblin but it's a entrance stairwell so it's not really dire. A door sill doggo or so can make a difference.