AFAIK, our shed has been in place for 20 years or so: it was here when we moved in 7 years ago, and I think it predated the previous owners,
I had bought new shingles already but hadn't installed them yet, but after last week's Midwest storms it was obviously time to tackle the job.
The first thing I found was that they had started with a row of shingles turned upside down, which I had just read is the worst of the three common ways (and illegal in some jurisdictions), best being to use a special starter strip (which I had already bought) and next best being to use shingles the right way up but with the tabs cut off.
Next I found that none of the protective strips over the adhesive had been peeled off!
I am assuming that this was a "kit" shed, but I have no idea whether it was the vendor (or the vendor-contracted installer) or the earlier homeowner who erected it.
Perce