Leak? Check the Roof Vent Flanges
First, I’m not a roofer.
There are many usual suspects when it comes to roof leaks. I’d say the most common that I see are either a lack of roof flashing, or a faulty vent flange as was the case for this repair.
One of my clients was noticing a water spot on the drywall above the vanity in their half bath. Stepping outside, it was easy to see that it was in the vicinity of a 4″ pipe that vents the plumbing system through the roof.
Once I got up on the roof to get a closer look it was obvious that the old rubber flange had deteriorated and had large cracks that was letting water get into the house with little trouble.
Time for a new flange.
The key to this is to be careful- not only to make sure you don’t fall off the roof, but to carefully loosen and lift the shingles surrounding the old roof flange so you can lift it off of the pipe, install the new one and then nail the shingles back down. The top side of the flange goes under the shingles above the pipe. I can usually do this without damaging the shingles and all is well. However, if you break a shingle, you may need to replace that as well.
I like to seal around the new flange with some good roofing cement, especially the two exposed nails at the bottom of the flange. You can see that this one fits more snugly around the pipe and will keep the water out.
Bruce