Pottery Barn tells me that a sofa that they have with overall dimensions of 80w x 36d x 36h will not fit through my doorway. They say that the diagonal depth of the sofa is 32 and that's what determines whether or not it will fit. However, the sofa has removable back cushions and the actual back of the sofa is 29. Will it fit through the door?
Having moved several sofas myself, it's very doable. Of course you can't just set the sofa flat and breeze it thru the doorway.Remove all cushions. Get a friend to help you. Tilt the sofa forward at an angle and see if it will fit in the doorway that way. You may need to remove the legs. My huge sofa was brought in by standing it on end, and moving the sofa back thru the doorway, then turning it slightly to get the seat portion in the door. Professional movers do this all the time.
The reason they calculate diagonal depth is because that is how it would normally be carried in. From my experience with very narrow doors: You could try to stand it on its end, and then swivel it in as though there is a dowel in the corner of the L shape, like someone else said, but I would make sure to check the following: 1: that you have some sort of moving blanket to put the sofa on so that it slides easily. 2: that your door is high enough for the length of the sofa 3: That there is room inside the doorway to turn the sofa to bring it fully inside 4: That there is enough ceiling clearance to tilt it back down once it's in. If you want to carry it with the back facing down, (which you think is the same measurement of your doorway) I would say to check that 1: there is room inside and outside the doorway to angle the bottom legs in 2: That your door moves all the way out of the doorway. I have a 30 doorway but the door bumps into the steps so that there is really only 28.5 of clearance - check it fully! 3: if you can take a tarp and somehow tie it inside and outside so that it is spread flat around the door frame and covers the doorjamb so that nothing gets snagged on hinges or lock mechanisms, and it may make the couch slide easier if the fit is tight. If it is a leather couch consider sacrificing a sheet or tablecloth for this purpose. Or even just get two extra people to spread it out and hold it taut instead of tying it. It can be a couch party! Another option would be (in the off chance you haven't thought of this) to check if you have other bigger doors, like a sliding patio door, which might mean more carrying outside but less manouvering to get it in etc. Then of course you need to check any internal doorways to make sure it would fit those as well.
Furniture stores know what they are talking about with measurements so I would trust them. They also know whether the piece has anything removable that could make it fit and apparently this piece will not. Work with them to find something you like as well that will fit. I worked in high end furniture stores and the biggest issue was getting people to understand what would fit and not. Also be very aware of the pieces size in the room you want it to go in. If could be way too large for the room as well.
It depends if the Arm rests are lower each side than the back of the Couch, then it is possible to put Couch upright and loop it around door like Waltzing, if you have clearance either side of Door. It is possible if you take the Door off you might get it in as you will have two extra Inches and the Door wont be in your way, also if Couch is made of soft enough Material then it might Squeeze in the Door with a bit of effort. You must be careful of taking off Wrapping in the hope of getting it in Door as there will be no protection to Couch and it could get easily ripped, so it is better to leave the Wrapping on for protection and not take it off. You will have to Judge if it is worth taking the risk of taking the Wrapping off or not. Is there a possibility of a Rear Window Access to your living Room or even taking the Window out or a back Door into the Kitchen and then into living Room. Good Luck anyway. Ps The Furniture Shop has to cover themselves in case of Lawsuit and have to be cautious in their statments . I have been in the same situation myself and said Furniture would not go into a Customers House but when we arrived at House and Pushed and shoved it sometimes Miraculousely goes in and we are even surprised ourselves . But mostly the Shop knows from past Experience of different Localities if it will go in or not , it depends if People have done Alterations to a difficult house and then might go in.They tell you it is at your own risk if something goes wrong if they know it is going to be difficult.