Shingling a lean-to shed that's very non-rectangular

So, I’ve got a lean-to shed that’s 5 sided and I’m not quite sure how to start shingling it. Usually you’ve got rectangular roofs or sections of roofs and it makes starting the first course pretty straightforward.

I made a sketchup model to sort of show you what I’m talking about. It’s incomplete but hopefully gives you an idea. The roof is flat and level there at the front and slopes down toward the point in the rear back at a bit more than 2:12 pitch. Please ignore all the extra lines and the rafters that extend beyond the roof area. Didn’t have time to trim in the model.

So I’m thinking I start my layout lines from the top and snap them all the way down till I get to the point. I guess I put starter strips along the two rearward edges? Overlap them in the corner? I figure I’ll flash over the corner and over the shingles on the front 3 edges ? Anyway, just looking for advice. I’ve only done asphalt shingles once on a small rectangular house with a ridge, and there’s a million how-to videos out there that helped with that. This one seems a bit unique and I just don’t want to do something stupid.

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Here’s a photo if that helps.Click Here

At 2:12 it shouldn’t be shingled. Looks like a good roof for self adhered modified, or your low pitch roof of choice

Is it all pitched the same direction?

The Owens Corning product sheets state it can go down to 2:12. I actually sloped it at about 2.5:12 just to make sure. It is all sloped the same way. I would really prefer shingles as all the low slope treatments I’ve seen are not particularly attractive.

Well, if I were to shingle that shape I would run drip edge on the lower sides. Overhang the starters if its normal where you live. On the upper sides I would have flashings that wraps at least 4" onto the shingles.

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Thanks a lot! I think I’ll give it a shot this weekend and see how things turn out…

Once you get your underlayment on you will get a better idea of how you will need to snap your lines. I am assuming the low side is the back of your picture so top down will probably work best. If you snap the first line, run a few courses, and then double check your measurements. You can always snap another line or two to make any corrections. At that low of a pitch you will never see if you have to make a 1/2" correction once you get to the wider part.