Even before going around back to see what the roof had to show, I was able to confidently say to my client that I suspected a second layer of shingles over the first. The roof looked newer, but the plumbing penetration sleeve was covered with black goop.
"How do you know that?" was her question.
My answer - "Experience."
Roof tar, or what I call "black goop," is what a non-professional will use for roof repairs. It does not last long, being deteriorated by the sun's UV rays, and it cracks and leaks.
Even from the ground my client could see the black goop, front and rear, slathered all over the plumbing penetration sleeve.
Why do they do this? Because they wanted to put a second shingle layer over the first without having to fit new sleeves under the first layer. Too much work! So they sealed previous cracks or gaps on the old sleeves with the tar.
The second layer of shingles is clearly visible at the lower left.
Black goop is a fine product, when used UNDER things like the edges of a ridge vent, an attic fan or other flashed locations on a roof. But it should be hidden from the sun. If so, it lasts a very long time and is an excellent sealer. Professional roofers use it! But they use it properly!
The next door neighbor had also re-shingled the house. Their roofer, an obvious professional, cut the shingles properly and protected the plumbing penetrations with new sleeves.
Showing my client the contrast with a side-to-side comparison was an immediate and valuable object lesson in proper roofing.
When I see black goop improperly used, it is an immediate red flag.
And when we could see the leaking and rotting of the roof from the inside the attic, my concerns were warranted.
A second layer of shingles is not necessarily a bad thing. It is commonly done. But it must be done properly or the homeowner is set up for future problems. Thinking that there is a new roof homeowners are lulled into a false security and unconcerned about what can be a brewing problem.
My recommendation: look for black goop! And if you see it, look also for other signs of unprofessional work. You are likely to find them!