Re: Ceiling/Wall depressions?
I suspect two things, ghosting and bowed lumber.
Ghosting is caused by condensation forming on the framing member where there is less insulation than in the open bay between framing members that insulation resides. Wood does not have a very high R-value. This difference in temperature causes mild condensation and dust sticks to the condensation, causing "ghost" lines where framing members are.
Bowed lumber is typically a problem at the time the home is built. If the lumber is allowed to dry out before it gets installed, it will twist, warp, and bow. Builders who are conscientious about this face the bows in one direction, lessening how noticeable they are OR the lumber is culled and not used for framing (works great as blocking and other small necessities). I have been in homes where the builder didn't care in the slightest where walls had huge lumps and bumps in them.
If this is a ceiling problem, it is possible that the lumber is spanned longer than it is capable of, causing it to bow with the weight of the drywall, insulation and other things.
Fixes? This gets tricky, as without a site inspection by the helpful folks of this forum, we can't even begin to assume the actual cause or course of remedy. For this reason, I suggest finding a local professional to assess these issues for you.
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