Home inspector Jay Markanich is in Virginia but his advice in the second to last paragraph "Always have a home inspection before the final walk through of a new home." is valid in Central Ohio. Not only old roofs leak....
When a roof abuts anything, there needs to be some sort of flashing to prevent water from getting between the roof and what it abuts.
On a recent inspection on a one-year old house I noticed something missing. Flashing. I looked everywhere. Still could not find it. I called, held up a box of treats, called and called and no flashing showed up anywhere.
I looked around the neighborhood. There were five other houses like the one pictured here. Only one had been flashed correctly.
That is more than disappointing.
What you are looking at is a roof that was completed before the brick work. Sometimes, often, well usually, the bricks are installed first, but not in this case. These shingles actually extended under the bricks! After the mason was finished placing the bricks along the roof line, the roofer should have returned to install flashing. He probably didn't because it would have required cutting each shingle to fit flashing underneath.
Properly done, there were be "step flashing" installed under each shingle, starting from the bottom and all the way to the top.
Then that flashing should have been sealed against the brick. They usually use a black tar material. But that can look a bit erratic and unsightly. It's unsightly appearance can be corrected.
On top of the erratic step flashing is installed a counter flashing. This would be a solid strip, cut to fit appropriately, which begins at the bottom and runs to the top. The counter flashing leave a nice straight line, and actually adds another layer of protection to the step flashing.
When done, the two together provide a very good water seal.
In the case above there was no such seal, as you can see. Inside this roof the ceiling forms one of two very pretty cathedral peaks in the master bedroom. What do you suppose we saw inside? Your guess should be staining and evidence of leaking. And this after only one year.
Of the other five houses in the neighborhood, only one was done correctly, as I said. One looked just like this, two had step flashing only which had not been glued to the brick (!!), and one, interestingly, had only counter flashing, which did not even reach the shingles! On that one not even mortar was placed to fill the space... I was tempted to knock on their door, but withheld.
Keep in mind, this is a one-year old neighborhood. The builder's supervisor was there every day and never noticed this? Not to mention the county... Paaaleeeeease...
My recommendation: Always have a home inspection before the final walk through of a new home. This is the kind of thing that a home inspector would have caught on that inspection. Don't buy the builder's line that there have already been many inspections on your home before your walk through and that the supervisor is there every day to make sure things have been done correctly. There is no guarantee that they have been!!
Personally, I usually have more problems on brand-new homes than on older ones. FYI