discolored but above that the wood is rotting and the insulation is holding that extra moisture. Mold can also be a problem, it can hide in places that you don't normally see and cause health problems.
The reason why it is so hard to find a leak sometimes is shown in the picture to the left. The water comes in at one point but doesn't come straight down. The water will sometimes follow the rafters, decking, chimney, or ceiling joists before it comes inside the living area. You might see the ceiling getting wet or
It's never fun when your roof is leaking and sometimes it can be tricky to find it.
Chimney Flashing has been a common point where leaks happen. Chimneys take time to work around and it can be labor intensive which makes it one of the places where roofers tend to cut corners. It takes time to cut into the mortar lines and tuck the flashing into it and then reapply mortar into the bricks. By doing this it protects the roof with multiple layers of flashing so the water cannot find it's way inside the house from driving rain, ice dams or flowing down the side of the chimney.