Advice needed on constructing a small perimeter foundation
I'm going to erect a small greenhouse (10' X 15') on my property and am planning to set it on a perimeter foundation, and then lay bricks-in-sand for a floor. I'm pretty experienced with carpentry and remodeling, and have poured slabs before, but have never built forms for a stem wall. I'm trenching down 18" and pouring a 10" wide by 6" thick footing, and then I want to pour a 2' high and 4" thick wall on top. That would give me a perimeter wall that stands 12" above grade.
I have a cement mixer that can do about 3 bags at a time and will mix and pour myself. What is the most inexpensive material I can use for my forms (for example, can I use 1/2" sheathing)? How closely spaced do the metal ties need to be? Do I need to build the forms for all 4 walls at the same time, or can I maybe do two walls and then re-use the form materials for the remaining two? Given that the weight of the greenhouse is only 1200 pounds, what's the smallest rebar I can use?
I'd appreciate any input on how to do this easily and cheaply. If anyone knows of a good do-it-yourself book on this subject, please mention it. Thanks