Darks Spots On the Outer Edge of Ceiling – Why?

I have a 12-year old ranch style home, and have a question about the ceilings. In the last few years it's developed dark areas where the sheetrock was screwed to the trusses. This is only at the outer edge where the ceiling meets the wall.  I assume this has to do with the cold winters.  The ceiling is covered with a joint compound product with a random pattern.  Should I seal the spots and then paint? What do you suggest?  Thanks – I listen to you every Sunday morning!  Chuck

The Money Pit Answer

Hi Chuck - thanks for being a loyal listener.  As far as your ceiling goes, what you're seeing is a very common condition called ghosting.  It's caused when warm, moist air air rises to the ceiling, is cooled near the outer edge of the wall, and then falls.  That conductive loop essentially layers typical household dirt and contaminants in one place - that is, the coldest place, where it's basically just sheetrock on wood.  A lot of times you see this on the bottom edge of a ceiling joist, and sometimes in stripes.  Again, it's not a major problem, and is fairly common.  Given that, houses can always use added insulation, so use this opportunity to evaluate the insulation in your attic.  Try to get 10-15 inches of insulation up there, if possible.  Good luck!