Foundation question

mrmarkyt

Hello, before I start, I just want to say I have a question about a foundation for a workshop that I am building.


Instead of hiring someone to pour the foundation walls for me, this is my plan, tell me what you think.

Dad has a trencher that will go down about 38" and 8" wide. We want to use that to dig a trench. Then we will put in vertical and horizantal rebar into that trenched hole. Then pour directly into the trench, leveling it off. Then as the concrete is couring, we will insert more rebar every 4', into the foundation 12" and sticking up 24". That rebar sticking up, will be used for the 3 courses of concrete block that will finish out the foundation, putting it 24" above ground level. Those concrete blocks will be placed after the foundation is dry.
What do you think?

NJ Brickie

I see a few things you need to address. First what is the frost line in your area? your footing must go down that far. Second what size block do you plan on laying? Typically a footing must be the thickness of a block (8") and twice as wide ( 16" for an 8" block). Your trencher is not wide enough. Third there a some, not many places you can not use earth forms for footings. Check into it. And if you are laying 3 courses of block you would not want the rebar sticking out of the footing 24", Stick it out somewhere around 20" gives you alittle wiggle room and there is no need to come all the way to the top of the last course, half way up the last course is good.

Scuba_Dave

Where are you located?

mrmarkyt

I am located in Iowa. Frost line requirement is about 42", so after construciton is complete i had planned on adding 6-8" of dirt around the outside. That would meet the frost requirements.

I plan on using 8x8x16 block.

I knew the "footing" wouldnt be the recommended size, just didnt know if that would be a problem. I know of quite a few garages that were poured in that same method.

My other option I am considering is to excavate it all out, form out 16"x8" footers, and then lay 6 courses of block on top of that. Would that be a better option?

jomama45

Definatetly go with option #2, laying 6 courses of block in the trench on a 16" + wide footing. Here's the reasoning in my opinion.

- The trench will never be straight enough no matter what.
- The code in my area, footing width is wall width + 4" per side of wall MINIMUM. We always pour 20" wide footings minimum, as your footing forms will never be perfect.
- Even if you could trench perfectly straight, you would still need to line both walls of the trench with foam insulation, plywood, etc.. to have a smooth enough finish so the frost would not "pick" at the poured wall. Now by lining the trench, it's too narrow.
- Most inspectors in my area will only let us use the depth of the footing in the minimum frost depth equation if it formed. If we "bank" pour the footing, we need to add an additional course.
- I've often contemplated what your thinking of doing on small jobs, & have never found a way to do it effeciently, & more importantly, never thought it would perform as well as the conventional way.

Hope this helps your decision.

jaros bros.

Why have you ruled out a floating slab or Alaskan slab? Going this route is pretty straight forward and will cut out a lot of the cost.

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Josh Jaros Remodeling in The Woodlands, Texas
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jomama45

I've been in & around concrete & masonry for 20+ years, & I've been to Alaska, but I can't say I've ever heard that term. Just curiousity, but it is the same as a floating/grade-beam slab?