I have a Shih tzu and wanted to know when your dog did certain things and at what age? 1) When did your dog go up and down stairs? Charlie is 6 months old and does not go up or down stairs yet. 2) He does not seem to be gaining that much weight. I have seen many shih tzu's many sizes. At what age did your small dog stop really growing? 3) How long did it take to be 100% housetrained? It appears that we are not, but im very paranoid!