A metal flashing may also help with the water intrusion problem and lots of caulk under the mudsill before you attach it to the concrete if you go that way.
OK get the plastic/pre-fabbed shed, use your existing concrete patio as the floor. Then just use a good all weather silicone sealant around the bottom between the walls and concrete floor. You may need to touch it up every year or so but it would be a lot easier than building a permant type shed.
I manufacture steel building parts and those pre-fab shed guys have it down to a science. I can't touch what they are producing pricewise or ease of assembly.
Get a door with a threshold, and then just seal the whole shed to concrete floor and be done with it. That's how I'd do it anyway.
Chris
A metal flashing may also help with the water intrusion problem and lots of caulk under the mudsill before you attach it to the concrete if you go that way.
I don't know if this would work for your project, but we built my son's clubhouse up off the ground.
http://i86.photobucket.com/albums/k8...a/DSC00215.jpg http://i86.photobucket.com/albums/k8...a/DSC00216.jpg