I am noticing many cracks starting to appear above doorways. I think we do a pretty good job watering the outside of the house. What are possible causes of this? The house was built in 1980. We bought it about 1.5 years ago (it used to be a rental) in the Dallas area. I am also noticing lumps starting to appear where the wall meets the ceiling ... looks like the nails are being "pulled" out below the paint surface. Any info will be greatly appreciated. Thanks... Burt