The area that is darker is where a row simply fell out. The shingles that fall out are narrow and flat unlike the top row that is what one would consider normal sized with shingles. This wouldnt alarm me but its done this on about six places. In each instance it was on a VERY steep section of roof. The ones that have come loose have all done it on 100 degree days and were held in place by only the tar strip from the layer above i.e. no metal fasteners of any kind. I have only done conventional old school shingles where every single piece gets nailed down so my very armature roofing background has never included this type of shingle. Any input from those who can answer how alarmed I should be would be greatly appreciated.
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