foundation prep on a slope - quonset hut

[Chrispy]

:shock: Here is a question. I am planning on creating my foundation for a 30 x 40 quonset hut in my back yard. I am sure the neighbors are going to love it! The yard is sloped about 4 feet over the 40' length of the building. My plan was to split the difference of the slope. In other words my plan is to dig into the hill 2' for half of the foundation and build up the other half by 2' with crushed rock (after scraping off the bio layer).

The first question is whether or not this is a good approach. Second, I was planning on preping the entire site with crushed gravel and building my forms over the gravel pad. Is this ok and if so, how far beyond the perimeter of the foundation should I spread the gravel?

My main concearn is not having to dig into the hill side too much because that will require retaining walls and possibly put the shop floor too low making me nervous about moisture issues.

Finally, does anyone know anything about reject gravel. A co worker of mine used it to prep a site for a pole barn and says it is 3/4 minus admixed with dirt. He claims that it packs just as well and is a lot cheaper. I am only putting a quonset hut and would not consider this for a house but should I consider it?

Thanks in advance.

[Pokey]

In my opinion i would excavate your foundation 2' down in front as you mentioned, and then when it gets to the point that you are getting ready to meet up with grade drop you excavation 2-3 feet so that your footings will bear on virgin soil. If you build up your lot as you mentioned you really should have a soils engineer inspecting it and that is just more cost and more time. In most simple foundations to jump foundation heights 2' (as long as the total height is not over 8' tall) is only about $10 to $15 per linear foot extra. Also in your area is frost prection not an issue. around here you have to be at least 30" below finished grade.

[Chrispy]

I think that is what I will do. I think I will get a good excavation person to prep the site and then make the forms myself. And I will do as you have suggested - making the foundation taller on the low side.

Thanks Again.