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Foundation on sloped land

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  • Foundation on sloped land

    Hoping to build the Casa 100 (probably a corner installation). My site survey has turned up only one suitable location on my land. Unfortunately its on a slope (the orientation is such that as I face the oven opening, the higher ground is to the left, the lower ground to the right). The instructions I have found only talk about slabs / foundations on level land. My questions:

    1. Do I need to put a french drain or equivalent to the left of the oven to deal with water runoff?

    2. Since the right side of the foundation will be sticking out of the ground more, do I need to dig deeper and pour more concrete? Or can I get away with a thicker layer of gravel and more concrete on just the right side? I'm guessing the right side would be about 8-10 inches lower than the left.
    Maybe I need to just dig the trench I mention above deep enough, which
    might make left and right same levels?

    3. Build site is Raleigh, NC, wondering if I need to worry about the frost line? Googling (surprisingly) turns up little to no info on this (guess I need to try some different searches).

    Thanks in advance,

  • #2
    Re: Foundation on sloped land

    Welcome Tim.

    You can do a gravel base or floating foundation. Just make sure the ground slopes away for drainage...and a french drain/pipe won't hurt.

    How about a pic?
    Sharing life's positives and loving the slow food lane


    • #3
      Re: Foundation on sloped land

      Thanks for the reply,
      Here's a picture, the slope may be a little deceiving, probably didn't have the camera level. The oven will probably have to go towards the right of the picture (there a buried cable TV line I need to avoid, although I could get that moved). I will have to take a few branches down, but should have plenty of clearance to the trees.

      I have not heard of a floating foundation, can you point me to more info?


      • #4
        Re: Foundation on sloped land

        Search the site....

        it's basically a layer of crushed stone or gravel that is well drained (to avoid frost heave)
        Sharing life's positives and loving the slow food lane


        • #5
          Re: Foundation on sloped land

          I have a floating foundation and it works fine for me. I guess I put in about 5-6 inches of crushed rock and then poured the foundation.

          When I got done with landscaping (meaning planting elderberry bushes and iris) around the outside I buried the foundation and up the block about 6-8 inches on the back side. This seems to cause water to run thru the base of my oven. I definately need to dig out the back and install a drain pipe. Should have done it in the begining.

          That's my experience from Graham, Alamance County, NC. CHUCK

          PS - I think we have 5 or 6 ovens in the Triad & Triangle areas now who contribute to this forum.


          • #6
            Re: Foundation on sloped land

            I'm also in NC and my data supports Chuckster for this area.

            Here's what I did with my slope issue:

            My oven and outdoor kitchen had a right to left slope and the ground (red clay) was so hard, I ended up pouring 3 floating slabs at different heights as the ground level changed. I drilled holes into the edges of each slab and used rebar to link each slab together (kinda like dowels in wood)

            Right wing is highest and metal stud base cabinets are built right on the slab. Oven slab is a bit lower and I just filled in the wood storage area with gravel to bring it to patio height. Left side was poured about 10 inches lower than right side.

            I leveled up the left side with a course of 8 inch block, filled the cores and center with rubble from building the oven, framed around the block, laid a bit of rebar/mesh, and poured a top cap that filled the cores and covered the rubble.

            I was a bit concerned that my slab thickness was 1 1/2 inch or so over the block so I used a bag of my fiberglass reinforced cement (originally purchased for coating the oven block base) mixed with the concrete for extra reinforcement. It's been a year now and it all looks good. In hindsight - I should have measured better - I could have poured the base slab a bit thinner and had no worries.

            Some folks on this site have also built up slabs with multiple layers of block and concerns have been raised that leaving open cores in blocks may lead to freezing and damaging the foundation. I would fill all cores in below ground level courses.

            My oven progress -