OK, so it is probably steel, but it still has a nice ring to it. The old shed at our new place could use a little love. It is 10 years old and the fasteners that hold the metal roof down appear to be in bad shape. The tops are all rusted and the rubber washer that keeps water out looks rotted. I pulled a few, and luckily none appeared to be rusted below the surface.
The shed seems to have a constant supply of leaves on top. In fact, I think that branch has been up there since before we moved in.
Some of the leaf piles had been there so long they had decomposed into a dirt/compost looking substance. The surface finish of the roof looks really rough in places.
I swept off all the leaves and debris, then gave the roof a pressure wash to clear the rest of the dirt and prep the surface for paint. Before painting I went through and replaced every screw on the roof with a new longer one.
Pressure washed on the right, not yet on the left 
All clean
Once all the screws were replaced I sealed everything in with two coats of a siliconized roofing compound. It looked a lot like super thick paint. Putting it on really heavily, a 5 gallon bucket gave me two coats with a little left over.
I spilled over the sides in a few places, but otherwise it all turned out well and looks nice. I hope this buys the roof another 10 years before I have to do anything. I know walking around up there was bending the sheet metal up, so I won’t make a habit. I do need to sweep off the leaves a few times a year though. That should be an easy job with a long broom and a ladder.
Kilted Craft Works 