Every winter, we get cracks like this where the walls meet the ceiling in certain rooms. We just got our bathroom redone, so it's most bothersome here. When springtime comes, they "seal" back up. Why does this happen and what's the best way to fix this? Or should I just hire someone? How much would this run minus painting?
Update: thanks everyone for your answers! ultimately, I think the best answer is the "cover it up with crown moulding" since that will look prettiest, add some value, and fixes the issue for the long term. But is that what I did? Of course not!! I went the "caulk it and hope no one notices" route, and, honestly, it looks pretty OK now. I used Lowes White Lightning Latex Caulk and filled in the gaps, then painted. I think there is still a question of how it will look in the spring when it closes up, and if it will "bead" when it compresses. I guess we will see. (FYI there's more info on why this happens in this article I found — he also endorses the caulk solution: http://www.chicagotribune.com/classified/realestate/sns-201401131900–tms–askbildrctnab-a20140124-20140124-story.html)
Best Answer
The reason why this is happening is the structural members are expanding and contracting with the temperature/humidity changes.
There is no good solution to fix the issues, but you can cover it up.
The quick and dirty solution would be to put up quarter round over the seams, and attach it to the studs only- That is not to the ceiling. This would allow for the expansion/contraction to remain covered.
Other options would be to install Cove moulding.
or Crown Moulding
Note that the Crown shown here is clip on, and the clip attaches to the wall only. Again, this allows for expansion.
These can all be DIY projects if you're comfortable with finicky work. It's a bit tricky to get the corner mitres looking nice and tight, and you'll need a compound mitre saw.