We have a duplex in southwest Florida with subfloors. In December for the last 3-4 years cracks have appeared where the ceiling and walls meet at some of our interior walls but not exterior or common walls. The cracks vary in width with the largest being about 1/4 inch. One bathroom door sags so force has to be applied to close it and it will not latch. About 2-3 months later the problem corrects itself. All of this takes place during our dry season so rainfall is not an issue. Several general contractors have gotten in the crawlspace below during the problem time with a laser and said everything is level. We need resolution so it does not continue to happen.
I know the cause, (at least in part) just not the resolution, if any exists.
Wood absorbs water (or loses it) to/from the air. In humid season, it swells like one of those foam shapes in a pill capsule you can get from the dollar store (ok not quite so bad). In the winter/dry season it'll shrink again. Depending on when it is installed, it could have been very swollen.
My issue is more cosmetic. In rooms where crown molding is installed, the seams (including some mid-run seams) have separated a good 1/4" in some cases. Additionally, the crown molding has pulled away from the ceiling giving a "torn" look to the paint.
The issue at hand, then is to humidify our homes. The question is the best/cheapest way of doing so. I could install a humidifier on the cental air system I suppose. Luckily doors actually work better during the dry season. I only have 1 door that sticks a little during the summer/humid season so it's not a big issue.
I'm curious as to why it's so bad this year. I've been in this house for 2 1/2 years and this is the first time It's pulled apart like this.