About 10 years ago I build a 12 X 16 shed and decided to use the Ondura corrugated panels on the roof. I was looking for something other than shingles. They were not that difficult to install and required less time than tar paper and shingles. As a matter of fact, I did not even install sheathing or plywood - I just spanned across the joists with scrap boards and nailed into those. If you do that, just be sure to space those boards a maximum of 2 ft. away, because the Ondura is somewhat flexible and won't hold your weight very well. Pay the extra money and get the special ondura nails with the rubber washers so the roof doesn't leak. And don't nail in the valleys where the water runs - nail through the ridges. I'm sure screws with rubber grommets would work if they were long enough, but the nails seem to hold just fine. I read on their site that the Ondura roofing may need painting after a certain number of years, but mine have not needed any paint even after 12 years. I've had pine tree needles and leaves fall on them every year, and they've held up just fine. The panels themselves are like one big, thick, molded asphalt shingle with a coating of paint. New ones do have an odor of tar and asphalt. My opinion is they will last a long time if installed properly. I have contemplated putting them on my house right over the existing shingles. I was wondering if anyone has done that and how long they've had them on. I was also wondering if I should first lay out a grid of firring strips first so there's an air gap between them and the old roof. Has anyone had to paint them? How do you install the Ondura panels so they create a seam where two roofs meet? What about things like vent pipes, skylights, and satellite dishes - how do you work around them? Any comments are welcome.