[Bantik]

I'm assuming that you don't have an attic or crawlspace above the living room ceiling. Is the chimney on an outside wall or does it run through the middle of the house?

If your chimney is in good shape, it shouldn't be possible for water to come down and get into the walls. As the house is only 8 years old, the chimney is probably not the problem.

If you can get a good view from the ground (maybe with binoculars?) check the area where the roof meets the chimney. Look for loose flashing or shingles that appear curled, broken or askew.