I understand that wood expands and contracts based on temperature, humidity, and other factors...
However in our house the doors are really subject to seasonal changes. For instance my bedroom door is perfect in the winter but has trouble closing in the summer - seems to move up the trim. My 2-year-old's room is the opposite.
Basically almost all of the doors in the house have a season or two when they are very easy to close and a season where they may barely close right. Wondering why some houses would have so much variance? - mine is a basic american ranch design - all doors mentioned are on first level.
Then to follow that up what can be done to prevent this from happening? Is there any bracing what is below/above to help this?