My home is in the shape of a U. The two story portion is at the base of the U while the single story living room and garage form the arms of the U. The living room has a cathederal ceiling and there is no attic above. Where the drywall meets the drywall attached to the two story part of the house a substantial 1/4" gap opens in the winter and closes in the summer. Just filling the gap with spackle fails because it just falls out. Its ugly and needs a fix. Can you suggest somthing?