I moved my business into a new building, and there is a doorway i want to put up a door in it. However the doorway is about 1/4" narrower at the bottom, than the top. Neither of the top corners are square. I am looking for the easiest way with the least amount of work and knowledge needed to hang this door. It is only a barrier, it is not for security. It will be closed most of the time, so i am not worried if it is going to naturally swing open or closed.
Also, the cuts for the hinges on the door and the frame do not line up. I am fine with buying a new door, but I would rather not replace the frame of i can avoid it.
Any suggestions?
There's a few ways you can tackle this with various degrees of rightness.
First of all, your door looks to be hung upside down. That's not going to affect the fit of the door but it is going to put your doorknob at an awkward height.
Your best bet is probably going to be to go get a new, pre-hung door, and replace the entire thing, frame and all. It's really not that hard, just kind of fiddly getting everything squared up properly. You can probably get it done for less than $200, and a few hours of work with a friend or two.
Second best bet is going to be to square up the existing frame, get yourself some shims a prybar, and some nails, pull off all the trim, and set it right.
In my experience, trying to get a new door to fit right in an existing frame is always kind of a pain in the ass. It sounds like more work, but it's usually worth it to go the pre-hung route.
There's lots of guides and YouTube videos on how to do all of that.
Least right- start modifying the door and/or frame so they fit. Cut, plane, chisel, and/or sand the door and frame down until they fit. Yes, the door is probably hollow, but you should still have probably about an inch or so of solid framing around the perimeter of it to work with. There's a good chance if you go this route you're going to find it looks kind of wonky and you're going to wish you did one of the above options.
You could always of course pay someone to do it the right way. Shouldn't be terribly expensive, I'm a cheapskate and will DIY most things, but I have a personal dislike of installing doors, so it's something I'd be willing to pay for.
Depending on how you can rearrange furniture, how much wall space you have next to the door, etc. you could also go with barn doors and just bypass the crooked frame entirely. I hat barn doors, I think they just look bad in pretty much all cases, but they're popular for some reason and pretty straightforward to install.
Depending on your tastes and how much of an actual barrier you need, may also be able to get away with bifold doors, a curtain, cafe/batwing/saloon doors.
I am worried about replacing the frame because I have seen the quality of work the previous tenants did and I have a feeling under that frame is worse than what I am seeing.
If the door frame is not currently falling out of the opening there's enough meat in the opening to mount a new one. Fondots is right. Re mortising well for the hinges and modifying the door to fit will be more effort than getting a pre-hung.