I have a chimney that leaks in heavy, windy rainstorms. I've had 2 or 3 roofers check it, and none found any significant problem with the roof, flashing or cricket. One did suggest waterproofing the chimney itself, which I did, twice. But I wasn't sure if it helped at all - it didn't stop the leak altogether, though maybe somewhat. The face of the fireplace gets wet, the plaster next to it gets wet, there are water stains on the ceiling above the fireplace (it's a one-story room with a hip roof), and sometimes there's water dripping down into the fireplace. I've had a cap put on also, but that doesn't seem to have helped. I'm going to try waterproofing again, but I'd welcome any other suggestions.