Would like some input on a footer/foundation, please.

[R. Barton]

Howdy, fellas. So this summer I'm going to build us a pizza/bread oven. For obvious reasons the first thing I'm concerned about is the base its built upon. I'm in central Missouri and our worst case scenario frost wise is in the 30" range as I understand it. I'm planning on digging down to about 40" and building the foundation from concrete block tied together and reinforced with rebar and concrete in the hollows.
I was thinking for the pad I'd dig down about 18" in the center, pack in about 12" of crushed stone and then pour a 6" slab reinforced with wire and rebar.

Now, my question is: does this sound right? Will this keep me out of trouble down the road?

TIA.

Rick.

[dakzaag]

Sounds like a lot of overkill, but hey, whatever floats your boat. One thing for sure, nobody is going to steal the foundation.

[R. Barton]

I guess my biggest concerns are the facts that this is being built on sticky clay that at times holds a fair bit of water. Just as an example; if you dig a 4' hole and walk away for an hour it'll have at least 12" of water in it when you return. Over night it might be half full. I'd just hate for the oven to be compromised by frost heave. Plus I have two teenage sons to dig the footing out while I supervise.

[dakzaag]

Every region of the US has a frost depth that foundations must exceed in depth to meet code. Here where I am in NW Indiana, that depth is 36". Ask any local contractor what the frost depth is and that is the depth that the footer goes down to. If you want to go deeper then that is up to you. Width of the footer along with depth of the actual concrete determines the stability of any foundation and typically the footer is twice as wide as the foundation block. ie, 8" block requires a 16" wide foundation that is typically 12" thick. For an oven, rebar is optional, but pretty cheap insurance to reinforce the footing. In my area, most foundations need to be poured the same day or next to prevent water from seeping in esp. during spring and wet seasons.

As for grouting the block, this is totally up to you, but considering most houses that have a block foundation do not have grout and rebar in the block, it is pretty much overkill in my opinion. It is cheap but if you want to tie in the rebar with the slab and continue it up to the oven support span, it gets time consuming to tie it all together. If you have willing teenagers who need the experience, then go for it, you will have a spare bomb shelter if Russia ever invades.

Masonry walls are very strong for compressive strength like holding up an oven or a 3 story house. Their weakness is in lateral stress like tall basement walls or retaining walls. Since you are basically digging a hole and filling it back in, the lateral stress is minimal so rebar and grout are not necessary. If you live in an active seismic area then rebar and grout are warranted. If you want to over spend on an oven, put your money into insulation and a fancy decorative exterior. If money is no concern then knock yourself out with rebar, grout, high strength concrete, fancy brick cladding, slate roof and copper flashing. Looking forward to seeing pics of your build.

[R. Barton]

Yeah I'm pretty sure here in the county 36" is the code requirement on footing depth. I'm still deciding between a block foundation or a poured one. Block would be faster, but if a poured concrete footer was cheaper material wise I'd go that route. I'm the proud new owner of a Harbor Freight concrete mixer so besides dumping bags, mixing the concrete shouldn't be too difficult. Obviously I've got lots of decisions to make yet.

[Toomulla]

the small amount of concrete and reo to fill the blocks in the base makes it good value for money

[dakzaag]

It comes down to how big the whole thing is. Just an oven without anything else is basically a square, 3' X 3' for a 36 inch oven with 12" overhang on the sides. 1 yard to dig and 1 yard to pour, easy peasy. If you are going for counter space and a table/bar area then you start talking about a fair bit of digging and lots of bags of sackrete. I agree with Toom that the rebar and grout is cheap, but getting it in the right place and attached to the footer and connected up through the top span is a pain in the butt if you follow general overlap procedure. Personally I have found gravity to be a reliable force and a brick oven is if nothing else, heavy. Have fun with that mixer, sometimes I wish I had one and then I think about hauling all those bags...

[Gulf]

I'm not really versed on frost heave, other than what I read on the forum. I am familiar with yazoo clay however. Swell with rain , shrink with drought. Digging down to the depth that is required in your area, filling with gravel, and then pouring a monolithic slab should allow the whole thing to rise and fall together as one imo.

[R. Barton]

Thanks for all of the input, gents. I think I'll just err on the side of caution and build an up to code footer so I don't have to worry about.

[agrasyuk]

Hi Barton,
I'm not sure about regulations in your area but in our climate zone (North Chicago) the code calls for foundation 42" below grade. The soil here is the most Clayish Clay that i ever seen so for me it made sense to dig full 4 feet down and have 6 inches of packed gravel under foundation to deal with water and frost. perhaps an overkill , but I have both peace of mind and village inspector that is satisfied. I used CMUs for my foundation - worked great

[agrasyuk]

Sorry for double post. Somehow I can't attach pictures from album once post is made

[R. Barton]

Sorry for double post. Somehow I can't attach pictures from album once post is made

Yeah that looks about like what I had in mind. Sounds like we have the same gunk for soil too.