Shed type roof to wall flashing

[Jon mackay]

I have seen this type of connection flashed 2 ways; under the shingles and over the shingles. I always thought that over the shingles is the correct way. Is it acceptable to install the flashing under the shingles as shown in the pictures?

[Scott Patterson]

If I'm looking at the pictures correctly, under the shingles is what is needed. If you put it on top of the shingles the water would run down the roof, under the flashing and into the house.

Anyway that wall is not flashed properly. That small 2-3 inch section of flashing is not going to keep out heavy rain. Really need flashing and counter flashing.

[Jerry Peck]

Scott,

Those photos were taken viewing down the wall (bird's eye view) at the shingles. The roof slopes away from the wall you are looking down.

In hurricane areas, that installation (over the shingles) could lead to loss of the flashing.

In non-high wind areas, it works okay when installed that way.

[Jon mackay]

Ok, So there are probably several techniques then.
I always though that the flashing was supposed to stay above the shingles to prevent water infiltration under the upper shingles.

Thanks for your help.

[Rick Cantrell]

"Ok, So there are probably several techniques then.
I always though that the flashing was supposed to stay above the shingles to prevent water infiltration under the upper shingles."

Yes, to prevent water from getting under the shingles the flashing must always be on top of the shingles.
If you will look closely you can see that the flashing is on top of the 2nd row of shingles, the 1st row covers (or hides) the flashing.

[Jerry Peck]

Yes, to prevent water from getting under the shingles the flashing must always be on top of the shingles.

As I said above, 'not must'. There are areas where that is just asking for trouble.

In the hurricane prone regions of South Florida, the flashing is sealed down to the underlayment, then the shingles are sealed down to the flashing.

NO LEAKS.

And, the flashing is not exposed to high winds, which could (would) rip it right off the roof if they were on top and left exposed, which would then lead to loss of the roof covering system.

[Rick Cantrell]

Jerry
I wasn't trying to dispute what you said or saying it would not work I've just not seen (or heard) of it like that until now. The "must have flashing on top" is the only way I've been taught. Anything else just does not seem right.
I have seen it flashed as in the photo, flashing on top of 2nd row, then 1st row on top of flashing. In the photo I do see nails through the 1st row into the flashing, that should have been no nails but just sealed with roofing cement.

[Scott Patterson]

The flashing like Jerry is talking about is very common in high wind areas. This would be all coastal areas and many other parts of the country.

[Jerry Peck]

In the photo I do see nails through the 1st row into the flashing, that should have been no nails but just sealed with roofing cement.

Rick,

That I fully agree with.

One does not install a flashing like that then violate it by nailing through it. That's just plain dumb.