Anyone over twenty, well maybe a little older, may remember the Great Karnak, a character portrayed by the legendary Johnny Carson. Karnak was a seer, a prognosticator of magnificent skill. By holding an envelope to his forehead, Karnak could recite the answer to the question on the card sealed inside the envelop. He would then tear open the envelop and read the question. His predictions were if nothing else, hilarious.
As a home inspector I am thought, at least I feel this way at times, to be able to predict the future. If this were so, I wouldn't be inspecting houses. However I can with reasonable surety in some instances predict how, for example, the installation of a component in a house will reach an inevitable conclusion based on what I find on the day of the inspection.
Recently I was able to see the result of a prediction I made from two years ago. The result was in no way a surprise.
A homeowner had contacted me, as I said two years ago, to inspect an addition being made to their home. They had gotten into a dispute with the contractor over several issues. They wanted an independent inspector to review and document the work thus far completed.
The addition was raising the roof at the back of the house to create a shed dormer, making more space in the attic, which would then be finished into bedrooms. The space would of course require a new roof and covering. Since a shed dormer has an almost flat to low slope roof (3 pitch or less) it should be covered in a roll type roofing material, not shingles. Ascending the roof, I found exactly that, roll asphalt.
So far so good. Then I saw the two plumbing vents protruding through the roof. Actually I noticed the gobs of roofing tar around the incorrect type of flashings for these two vents. The roofing "professional" had installed a typical plumbing vent flashing for a moderate to steep pitched roof.
This kind of flashing is meant to be installed with shingles. The top is tucked under the shingle above, the bottom left exposed, thus matching the lapped pattern of the shingles. I believe it would seem obvious to even the most inexperienced person, this is not possible with a sheet form of roofing material. So the solution the roofing professional used in this instance was to slather the edges of the flashing with tar. Tar is not flashing. It is not a good, long term sealant. At best it is a temporary, stop gap measure that can be used until a proper and more permanent repair can be made.
As the diagram I have included shows, properly flashing a plumbing vent with this type of roofing material is a bit more involved, requiring different flashing materials and methods. In other words, it takes more time and care.
Now viewing these flashings two years later, I saw what I had predicted. The tar had dried and was beginning to flake and peel.
I warned the homeowner that when the snows come this winter, inevitably piling up on the roof, leaks are quite likely to begin.
This conclusion wasn't hard to predict.