Building A Heavy Duty Shed Foundation
First let me explain what a heavy duty shed is and then I
will explain how to build the foundation. A heavy duty shed would be
something built similarly to a home. In other words you would use lumber
to frame the building and siding or stucco to finish the exterior. The
shed would also have a regular roof on it, using composition shingles or
something of its equivalent.
If your soil conditions are pretty good, I would recommend building a 6 inch thick foundation, with 10 to 12 inch deep perimeter footings. This would give you a sturdy shed foundation for a heavy duty shed.
To make it even stronger, I would install half-inch rebar or number four rebar, 16 inches on center, in a grid like pattern directly in the center of the 6 inch concrete foundation slab. This would give you a superior product and would probably hold up, pretty good in most soil conditions.
You should also install some half inch anchor bolts around the perimeter of your shed foundation, to hold the framing bottom plates in place. This provides a good foundation anchor for your wall framing.
If you're going to be building a shed larger than 12' x 12', you might want to get in touch with a structural engineer. Don't forget to check with your local building department, to make sure that you're allowed to build a shed that will not be removable on your property.
These are basic recommendations, for constructing a heavy duty shed foundation on your property.