Should rebar or steel poke thru foundation

[Dino_Pizza]

I'm digging my foundation now and am a bit confused. I know to lay in rebar in upper and lower portions of my 12"x16" perimeter footing and to put rebar every 12" both ways for the thinner slab area in the middle. I plan on having steel rebar in every-other block hole (all of this per the official Pompeii plans and others posts).

BUT...do I put vertical re-bar sticking out of the top of my concrete pour for every block hole I plan to fill with concrete? AND...if I do, do I just do my best to screed, level and float between the rebar? Please take a look at my attached pdf drawing and you'll see my question in item #3.

Thanks (in advance) for all your advice.
Dino

[Breven]

Re: Should rebar or steel poke thru foundation

Dino,

I'm not an expert, but I can tell you the way I did it. I floated the foundation, went back and inserted rebar, 2 or 3 foot long pieces into pre-measured spots, directly through the slab and into the wet footings. Then, after setting up the first course of block (with a foot or so of rebar sticking up) I just tied longer peices to it. It was all really easy. Take a look at my web album and you can see what I did. Perhaps a concrete expert would have a better idea? This was my first time working with rebar.

[Modthyrth]

Re: Should rebar or steel poke thru foundation

That shouldn't be necessary. The shape of the stand itself is very stable, and the weight of everything keeps it very nicely in place. Once my cores were filled and dried, I actually tried to knock it over (to make sure it would be steady while kids were running around). Not a budge.

I did drill holes into my foundation and epoxy rebar in place for a wall to the left of my pizza oven stand, but that's just because the wall is only a single block thick and a straight line. I wouldn't bother with anything with 90 degree corners.

[Breven]

Re: Should rebar or steel poke thru foundation

Nikki makes a good point. It could be over-kill. Here in earthquake country however...I didn't hesitate to go with the more stable approach. Concrete cracks naturally. If there is nothing there to tie your blocks together vertically and horizontally- it seems to me that eventually cracks in the cores would cause separation between the blocks. I think this is why rebar is used? Not because its not stable right after the cores are dry, but so that it remains stable 20 years from now.

[Modthyrth]

Re: Should rebar or steel poke thru foundation

True, if I were in earthquake country, I'd probably over-engineer everything humanly possible. Can't hurt to add extra stability.

[dusty]

Re: Should rebar or steel poke thru foundation

Dino,
You don't have to have vertical rebar in EVERY hole you plant to fill, but a few pieces is a good idea. Say one in the corner, one on each end, and mabe a few more in between- like every three feet or so. And yes, measure out where you want them and sink them into your wet foundation cement. And like Breven said, you only have to have a short piece coming out of the foundation as you can tie longer pieces to those as you go up.

Good luck and have fun.

dusty

[staestc]

Re: Should rebar or steel poke thru foundation

I was wondering the same Dino, but I came to the same conclusion that Breven described, given that I can't see any other way. You pretty much have to screed and maybe even float, then insert the rebar, let it set up a bit, then trowel. I never thought of putting in short bits of rebar then tieing longer pieces to them. Not sure why you would want to do that. If anybody has any other ideas I would love to hear them!

Travis

[christo]

Re: Should rebar or steel poke thru foundation

I did not go for the vertical rebar - thought about it - but when pour time came I did not have faith that I could get the rebar to line up. My design - lets say - was not exactly stable at the time.

but I'm not in earthquake zones (today anyway). I flilled the cores with concrete a bit more than everyother one.

I think bent bar and sticking up from the slab would be best to tie the wall to the slab from a pureist standpoint. If you don't like that - you could bend a bit of a j on the end of the rebar and stick it into the slab after the pour as Breven suggested - that will give a nice mechanical bond. I might go that way as you have a bit more freedom to place exactly where you want it...

I have drilled holes in concrete and used the epoxy to tie threaded rod and rebar and think it works well (based on no failures and internet lore).

Preparing the foundation was by far the most physically demanding part of building my oven. You are past the hardest part!!!

Christo

[RTflorida]

Re: Should rebar or steel poke thru foundation

I would say yes, tie in the block stand to the slab in earthquake prone areas...ad south FL (Dade county specifically) to the list as well. I remember when I started my build we had a Miami member (can't remember who) that had to actually "L" bend the rebar uprights and tie them into the slab rebar...seems building code in south FL includes ANY structure (shed, barbecue, oven, etc). Whether you intend (or actually need) to comply with building codes, it is always good to know how it "should be"and build accordingly (nosey neighbors are good at reporting work to the local building dept or code enforcement). From a structural standpoint most areas of the country should not need any form of tie in to the slab...just lay your stand blocks straight and true, gravity and weight will do the rest.

RT

[egalecki]

Re: Should rebar or steel poke thru foundation

Dino, I set up a couple of rows of block on my poured and dry slab and marked where the rebar needed to go, and then I drilled into the slab about 1 1/2 inches. I sank the rebar into the holes, then built up the walls one row at a time, filling in the holes with concrete as I went. We filled every hole, not every other one, by the way. By the time it was dry, you couldn't push it over unless you drove into it. Add the weight of the hearth and the oven pushing down, and you have a pretty solid creation. However, I don't know about earthquakes, and we have them occasionally here- just little ones, though.

[Les]

Re: Should rebar or steel poke thru foundation

Dino - it's pretty straight forward. Mark the forms where you want the re-bar. Screed off the cement, really no need to float it really well because it will not be seen. Stick in some bar and start the block process. Here is a picture of how I approached it. After I dry stacked the block, I dropped in a vertical piece of bar and filled that core with concrete.

Les...

[Wiley]

Re: Should rebar or steel poke thru foundation

For what it's worth... I bent "j's" in the ends of 18 inch or so pieces and had figured out where the block holes would rest and after screeding and first float placed the rebar just like I was placing standard "j" bolts in a slab pour. No big deal. Once the slab had cured sufficiently I stacked my block. Placing the block over the pins of rebar which extended from the slab. I then bent rebar into large "u" shapes so that the rebar that tied the walls of the stand and were strengthening the hearth were one continuous piece, that start on the foundation slab, go up and bend over and thru the area where the hearth slab was later poured and then down into the holes on the opposite side. I then infilled the cores, locking the rebar in place. Here's a couple of photos of the slab with the pins and after the cores were filled and I was ready to form up for the hearth pour. If you look close you can see the curved rebar diving into the cores.
Hope this helps,
Wiley

[Dino_Pizza]

Re: Should rebar or steel poke thru foundation

Thanks to you all for the great answeres! And Wiley, your pics are great. I'll try to tie the oven floor slab in as well.

HERES THE PLAN: Like you all suggested, I'll mark the forms (thanks Les) and slip the "J" bent rebar in the wet cement at the 4 corners and 1-2 places in between. I wasn't sure about tying short pieces of rebar to longer pieces but I see now that is normal when encasing in concrete. I'll fill every other block hole with cement and tie in the oven floor slab too. (My city was the official epicenter of the last big earthquake in the U.S.A. and in the next quake, I may not have water, power or gas but there WILL be pizza!)

I'll be forming my footings this weekend and hope to start a new thread on this site with my build.

Thanks, Dino

[staestc]

Re: Should rebar or steel poke thru foundation

Wiley, that looks great. Thanks very much for posting those pictures! BTW, on the slab photo, what is the pipe for? (at least it looks like a pipe, not sure)

Travis

[Wiley]

Re: Should rebar or steel poke thru foundation

Sharp eyes Travis! That is a piece of 1/2" electrical conduit (plastic) for a power outlet that is located just around the corner of the front entrance to the wood storage. I wanted to be able to have lighting inside the firewood storage as well as originally I designed the storage area opening to accomodate a electric proofing box. I have found the proofing box works better if it is closer to the downstairs kitchen.

I'm sort of surprised more people haven't installed some sort of lighting for the wood storage area. Most are building with a single room (essentially a man made cave) and I wouldn't want to run into some of the nasties that live in such places without the benefit of light. I was thinking more of spiders and such like for those who live in AU and rattlesnakes for the Southwest and West of the US. Where I live has fairly benign creatures although the Brown Recluse is not to be taken too lightly.
Wiley