The ceiling was a bit wavy in our kitchen and there were some gaps (some an inch big) between the crown and the ceiling. I first filled in the huge gaps with joint compound, sanded smooth and then painted it the ceiling color. That worked great for a short time, then a crack developed. I researched a caulk that was the very crack resistant,DAP Dynaflex 230. That lasted for a while until just recently when the weather changed. Now there's cracks along the whole run. I could just add more Dynaflex caulk, or is there something else I could use that would keep me from having to do this every year?
Any chance that this happens to be a wall that runs through the middle of your house?
Your roof trusses are flexing with the seasonal temperature changes. If you go up into the attic space and look at where the bottom cord of your trusses cross over this wall, I bet you will find the they either were never attached or that the nails have pulled loose.
If this is what you find than you need to attach each truss to the top plate of the wall up in the attic. You can use a Simpson angle bracket or drive a single 6" decking lag through the bottom cord and into the top plate of the wall.
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