BTW, FWIW if your couch has legs these will typically unbolt or unscrew if just a few inches will make a difference.
I have to admit that I only opened this thread because I misread “couch” as “cousin”, and that seemed really interesting.
Good luck with the couch thing though.
Yeah one of my coworkers overhead me lamenting my problem to another coworker and thought I was talking about sawing Tim Couch in half.
I’d love to help you, but there isn’t enough information in your OP to determine a strategy.
One possibility is to saw a line along the rails at a very acute angle, kind of like the line your car describes when changing lanes. The point is, you will be sawing across the rail, but by no means at ninety degrees. The surfaces of the cut can then be glued back together later. Partner the cut section up with a new piece of wood screwed and glued from behind. Think of it like a splint for broken bones.
I’m still on the side that says, “Try again to get it upstairs in it’s current configuration.” Stand it on end (as has been suggested) at a strategic turn of the stairs.
Just a little nitpick here, and a glimpse of professional rivalry few dopers likely ever see. Don’t ask a carpenter to do this. Get a cabinetmaker! A cabinetmaker is going to have a much better grasp on the situation. 
The two shady movers and my big football player boyfriend tried for a solid hour to get it upstairs. They did every configuration possible. They even busted into the wall. Again, no dice. And now I have a busted wall to repair. The ceiling is kind of low so it can’t stand on its end. There are no rails on the stairs and it has that stupid turn at the top. There is no real reason for the turn. I was thinking about completely taking down the wall but I wouldn’t be sure how to do that either.
It is most frustrating.
Sorry about that, tramp, I was sure that was it. You wouldn’t believe how many hits you get searching the Post archives for furniture+take+apart. 
I swear such an animal exists, though!
bloody woodbutchers! :).
I would second the idea of taking out a window, if you have double hungs, you can get a surprisingly large opening by removing the sashes. It’s fairly easy and very fixable.
Sorry, the windows are all singles and small. 
I have really gotten myself into quite a pickle.
Sorry for not getting back sooner, the boards have been sloooooow these days.
Anyway, I’m not sure exactly how not cheap, I think it cost at least a couple hundred bucks, but for them, it was either do it, or have their den furniture in the living room, along with the living room furniture. (Their problem was a narrow hallway with two turns.)
Check with some local upholsterers, use the Yellow Pages.
It can be done. Of course, throw enough money at something, and anything can be done.
Seems to me that it might be less expensive to toss the couch, saving some of the fabric. Then buy something else well-made that will fit up the stairs and have it reupholstered to be like the old couch. Sounds stupid, but surely it must be cheaper than half-dismantling and then reassembling the old couch and rebuilding/repairing a wall.
OR… are you SURE there aren’t some legs/feet or other parts that could be removed to reduce the size enough to make it squeeze through?
I am almost tempted to contact you off line just to go down to Arlington to see this thing in person.
PBear is somewhat close in his proposed drastic last-ditch solution. I would not ever suggest screws and plates, as they do reduce the strength of the new joint. I’d use and actual wood joint, like a tenon or something. But that seems beyond your stated skill levels. Also, know that if you saw through the structure, it will reduce the length of the sawn piece by a fraction of an inch; that may affect how the fabric lays over the couch (it could end up being too loose).
Hey if you want to come to Arlington to see it, be my guest. The only problem with getting rid of the frame of the couch and upholstering a new one with the fabric is that this is a very contemporary style couch and the curves on its back match the curves of the other piece. I know that makes not sense but that is the best way to put it. If I didn’t have those other pieces, I would just sell the stupid couch.
Made it clear, I think, that I’m no expert. So, curious. What’s an “actual wood joint, like a tenon”?
Hmmm… well if you can examine thing couch closely enough, maybe you can find nails or bolts that you can briefly remove to let the couch’s frame “collapse” a little. Look for any joint and see if you can remove a few nails to let the pieces “fold”. By way of icky analogy, picture a human with a broken arm. The muscle, tendon and skin keep his hand from falling off, but now he can bend his forearm almost double. If you’re gentle enough, the upholstery might hold the wooden framework together long enough for you to hustle it up the stairs and put the joints back together.
Or you could just bash it with a sledgehammer and turn it into a big purple bean bag chair.
I FOUND IT!!! I knew I wasn’t insane.
Here’s a link link to prove it.
Hit yourself on the leg until you are sore. Use the saw to chop the couch in half. If wishes were fishes we could all fly away. Apply this principal to the two halves to get them upstairs, no trouble. Two halves make a whole so that should solve itself, really.
Don’t mention it.
Whilst imagining using a chainsaw to chop the couch in half, my mind wandered, and I ended up imagining a domestic accident where the small (one) hand held chainsaw took most of my teeth out and a good bit of my lower jaw. So be careful. I think it would really hurt.
Hi, professional furniture mover with twenty-plus years experience checking here. I can’t suggest anything that probably hasn’t been tried yet, except that sometimes if you turn the couch upside down, try to bring it in with the back on the couch turned towards the floor, hook an arm through the door, lift the other end as high as the ceiling will allow, see if you can pull it through. This works if the back is high and the bench(where your bum goes) is narrow. Can the ceiling be removed in the hallway outside the door(ceiling tiles)? If surgery is required, perhaps removing one or both of the arms is possible, one of my customers did this to a couch that I delivered that wouldn’t fit into his basement. With one arm(or both) the sofa will probably stand upright in front of the door and you can pull the bottom in. Good luck!
PBear: “Made it clear, I think, that I’m no expert. So, curious. What’s an “actual wood joint, like a tenon”?” --Like a mortise-and-tenon joint. Cut mortises into the sawn faces of the piece, then fit in a tenon. Cutting the wood structure and then using screw-on plates means that the load is now focused onto the screws instead of distributed evenly. Ideally, the cut pieces of wood should interlock somehow instead of relying on a butt joint (where the two pieces butt against each other).
Tramp, does it have arms which could be be removed like Iyamity says? His ideas seem the most reasonable so far.
I don’t know how I would get the arms off as they are upholstered too. The feet are also upholstered so I don’t know about them either.
My poor, poor couch.
Thanks JCHeckler. Got it, I think.