Improper starter course - 3 tab shingle

[John Chung]

What do you think is going on here? My first impression was an improperly installed starter course. But as I think about it, it may be that this top layer might have been installed directly onto a first layer without felt underlayment; so it's actually the second layer? This condition is pretty much the case around the perimeter of the roof. I would have thought to find more eave damage if it was an improper starter course, but I only found one place with eave damage.

295672956929568

[Rick Cantrell]

I think you have it right.
Looks like another layer of roofing was (improperly) installed over an earlier roof.

[Scott Patterson]

2 layers of shingles and installed improperly! Good find..

[John Kogel]

There is another possibility - they may have stripped off the first roof layer, but thought the original starter strip was good enough to reuse. Seen that too.

[brianmiller]

its improperly installed because ? two layers are allowed.

[Billy Stephens]

its improperly installed because ? two layers are allowed.
Starter Strips do not have tab slots.

[John Kogel]

its improperly installed because ? two layers are allowed.The slots in the starter strip, which appears to be old shingles, are lined up with the new shingles. The starter strip looks old and brittle. The OP says the starter strip has leaked and destroyed some of the sheathing. There is no underlay. Need more? :D

No warranty for two layers.

[Billy Stephens]

Need more? :D

Why Yes, I would like a bacon Sandwich. :)

[Ken Rowe]

its improperly installed because ? two layers are allowed.

Not everywhere. In this part of MN only a single layer is allowed.

[Lon Henderson]

Not everywhere. In this part of MN only a single layer is allowed.

Ditto here.

[Garry Sorrells]

I have been following this thread and have to say it would confuse someone dropping in that had no roofing experience. It may in the use of terms and regions.

The first picture shows that a roofover was done. The 2nd roof layer was incorrectly started. There is no starter strip shown, only the old (1st) roof shingle. The old roof shingle would not be called a starter strip. It may be the strip where they started but it is not a starter strip. In the OP 1st picture the starter strip is the strip under the original (old) first course of shingle.

Some regions may find it exceptable not to install a starter strip and to install the first course over the existing shingle and then to seal it (new shingle) down to old shingle. In that event the new shingle tab slots should not fall over the old shingle tab slots as shown in the first picture of the OP. There are a couple of ways to correct the OP installation but that may be for another thread...

One of the reasons to use a starter strip is so that there is something for the first course of shingle , lower edge, to seal to and resist lifting due to wind.

Personally I like to see the first course of the old shingle cut back (tabs cut off). Then a starter strip (new shingle) installed. Or better yet to tear off the first 36" and install Ice/Water Shield, since it was not there from the roof installation 20 or 30 years ago.

For general comment a starter strip is a shingle that has had its tabs removed and then nailed so that the rack/tar strip will be under the lower edge of the first course. Thus when it heats up and sticks to the shingle above it will offer resistance to being lifted by the wing. Nails in the starter strip are spaced so that they will not be exposed when the first course is set over it.

[H.G. Watson, Sr.]

At first glance, it appears the eave (to the hip) may have been cut back and that gutters have been retrofit/installed (incorrectly and) more recently than the newest roof covering was applied (to either the latest addition/extension) & the previous to different roofing materials were incorporated (into the earlier installed roofing at the valley). The gutter over the O/H garage door also appears (at first glance) to be a cut-back post-roofing retrofit.