1. Chimneys that are more than 3 feet down from a ridge line will need what is called a cricket. A cricket is a slope built into the backside of a chimney to shed the water away.
2. The slopes need to be step flashed correctly. There are several test to see if the flashing is incorrect. Gently lift the shingles, down a roof to wall slope, to see if there is step flashing. Confirm that the step flashing overlaps. Check for rot behind the step flashing. Make sure that the step flashing is appropriately covered by counter flashing or siding.
3. Check the siding and chimney caps to see if there is any possibility that water can get behind either. Siding here has gaps between the trim boards that need to be caulked. This needs re-caulked. The chimney caps have some metal seams that need re-caulked as well. Overall these 2 components are in very favorable shape on this particular roof, and will just need to be reconditioned.
Work on this chimney will begin next week, relocating the pipe behind the chimney, building a cricket, re- flashing the chimney with new step flashing and shingles, recommend caulk the trim boards of siding and caulk the chimney cap. This will stop this owner’s roof leak, we guarantee it.