On Tuesday, July 21, 2009 12:01:44 PM UTC-4, SMS wrote:
My sister in-law bought a plastic shed at Costco (Keter Bellevue) with
floor dimensions of 100.5" x 80.5".
("http://outstanding-keter.co.il/files/17185841_a.pdf")

Someone at Home Depot said that she should set it on a pad of concrete
blocks that sit on a base of sand and gravel, all of which she ordered
and had delivered.

I thought this was a pretty bad idea for a plastic floor shed, and that
it will be difficult to get all those blocks arranged into a level,
even, platform. I would have built a base out of pressure treated
plywood sitting on a frame of 2"x6" pressure treated studs, and set that
on level ground without using any gravel or sand.

But now that she's bought all that material, is practical to sit it on
blocks, placed in gravel, even if it weren't an optimal arrangement? I
also thought of putting pressure treated plywood on top of the concrete
blocks and screwing the plywood to the bocks, but that's a lot of screwing.

Hi SMS - the method you describe sounds a little haphazard in my opinion. I'm not very handy, but when I installed a base for my plastic shed, I found this article to be helpful, easy, and straightforward - http://storage.suncast.com/help-me-c...d-foundations/. This is for a wooden base and I think they had one for concrete bases as well but that was too much for me. Hopefully this helps!