Get out your work gloves...and rent a small dumpster. Rip out both layers and fix it the way it should have been done the first time.
On another note...the wall that was removed does not look like it was original...as there seems to be drywall behind it...Did the previous owner to that sub-standard work as well?
When I see these gross errors in building maintenance and repair it makes me worried about other issues in the home.
You can demo down a 8' section on the low side. Use shims to make match and rehang drywall Over an 8' span you shouldn't be able to see it. http://www.okcremodeling.com
Or better yet rip it all out and see what is hidden beneath! Sorry.
A ceiling beam would cover it...lots of faux beam ideas are on You Tube. A 3 sided box can be 1/2 inch shorter on one side and it won't be noticed. The box can be dry walled and painted the same as the ceiling or the wood can be stained or painted a different color to add architectural interest. I just hate drywall demo b/c it's soooo messy and I will do almost anything to avoid it :)
I would just patch it with drywall, as tight as a fit as I could get, tape, mud, sand, mud, sand, mud, sand, sand, sand, sand, sand, and more sanding, then prime and paint.
Tear it all out. Find out what they hid with the fire damage and make repairs then drywall the ceiling level. All the extra work is well worth it. And having a local drywall guy do the install and the mudding is not all that expensive considering the pain it is to do ceilings. You simply remove, check and repair, then paint. Let the pros do the heavy work.
hi Maureen o' Donovan I did just what you suggested dry wall with 1/2 in and spackled and spakled I should be down this weekend
Moreen thats one way but my freind you would be using alot of drywall mud to hide the hump it would be easy just to whats causing it to bow then repair it . Also celings are very critical work especially high celings
Why not use moulding to cover the area? Easy job & it would be an interesting feature.
I will throw my two cents in...lol. I would tear out the side with the fire damage ( if it had been done correctly it would have been pieced in and shackled). This will also give you a chance to see any corrective work done after that fire. If money is an issue, rent a dry wall lift and pick up some 1/2" drywall sheets and repair it yourself (not rocket science to implement).