In alt.home.repair, on Tue, 26 Jun 2018 17:44:02 GMT, sphillips72
m wrote:

We recently re-tiled the shower surround in our guest bathroom. The bathroom
is a smaller bathroom, 5' deep and 8 feet long. Anyway while working on the
tile, I noticed that the ceiling seemed to be lower at each end of the
bathroom than it is in the middle. So I broke out my level and sure enough
there is almost an 1 1/2 inch to 2 inch difference between the edges of the
room to the center. It's almost like a dome shape, or upside down U. Almost
like it's crowning. There are no cracks in the drywall. What would cause this
to happen? What can be done to fix it.

Leave it alone. It's better for singing. All the opera singers and
the best popular singers have vaulted showers.

I'd prefer not to rip out the drywall
since there is blown insulation in the attic.

Then don't do that.

Would the easiest solution be to
add furring strips to the high spots to bring it level with the lower ends and
add another sheet of drywall to make the surface level?

No. The easiest solution would be to do nothing.

How long have you had the house? How long did it take you to notice
this?