Well I have been working this for a few months off and on, but have run into a bit of a snag today.  So I decided it was time to make a thread so others can tell me how much better they would have done it, after all it is Arfcom.

My wife told me this year is the year we finish the backyard.  Yikes I thought.  I have to finish my workshop, finish the landscaping, finish the fish pond, and FINISH THE PIZZA OVEN.  

Now most of the other stuff I have a handle on.  I would think I am pretty handy around the house EXCEPT when it comes to concrete and masonry stuff in general.  Thus why the pizza oven portion of my backyard todo is being posted.

Taking it back a few months I poured a footer for a 3'-4' high corner wall.  I read that the footer for a small courtyard wall is not regulated if I keep it at 4' or under so that's what I did.  Then I decided since I have no idea what I am doing with masonry I would dry stack the wall and fill the cores with concrete.  That all actually went pretty well.  You can see here that the wall is almost dry stacked and I am getting ready to pout the pizza oven base.


So far so good.  So I poured the base and dry stacked the walls for the pizza oven and adjacent countertops.



So that was all a few months back.  Then recently I finished up my workshop and since the stucco guys were already on site.....  Why not have them stucco the oven/kitchen area..  You can see the workshop in the background.  It was just missing soffit and fascia at this point (finished a couple days ago so that gets checked off the todo list for the backyard)


Ok, ok, so now we are quickly up to real time this week.  I decided it was time for the structural hearth.  So I formed up some sides and laid some rebar.  The pour is going to be 3.5" and the rebar is 3/8" on a 10" grid.  I put it pretty tight grid since it has to hold up a bunch more brick for the oven before it is all said and done.



Then yesterday I poured the concrete.  Here is where I really shine at not knowing what I am doing.  The concrete started to crack a couple hours after I poured it.  I actually  spend the time on this pour to measure the water content (7 pints per 80lb bag) because I knew it needed to be done correctly.  Needless to say I am bummed watching it crack to shit yesterday and this morning and don't really know what to do about it.

Just after the pour.


A couple hours later, and this morning.




So now what do I do?  How bad does this effect the strength of the hearth since it has to hold up a bunch more weight?  The hearth is supported around the edges 8" by the block and if you notice I put a center support with block in the system too.   The whole hearth is 6'x6', so the farthest span for the hearth is 24" (from the inner edge of the outer wall to the center support).

I was thinking I could go buy some steel and weld a square frame under the hearth between the center support and the outer wall so it only has to span 12" instead of 24".  Am I overthinking this?

I guess I would have tried to use some type of natural stone underneath the concrete pour.
Maybe consult your local granite/marble source and ask them? I am not sure how well these stones hold up to heat, or if they could be put ovet the top of the cracked concrete.

Keep us posted....

Excellent thread.

I have no answers, just here to learn.

But, there is no way I could afford a pizza oven in my backyard.  I'd never stop using it.  Within a week I'd be buying new pants.

TRG

So you basically fry a pizza on that?  Sounds pretty cool, but like the poster above I'd need new pants after a week if I had one of those.

He's gonna add a covered 'roof' of stone/brick.

TRG

OP,

I'm curious how it turns out as well.

After I saw your post I did a few searches and found this. Maybe it will give you some ideas.

https://www.youtube.com/watch?v=jonKUT8USSw

Good luck.

Looks like shrinkage cracks, which is no big deal.  Did you keep the concrete wet after you finished it?

The part I just poured is the foundation so to speak for the oven.  So after this I have to put a layer of insulation, then brick up an oven dome.  

My concern with this pour isn't so much the aesthetics, it will mostly be covered.  The problem is it has to support a othe 1000 pounds of bricks and what not for the oven itself.

Tag for future photos.

I'm going to be making an oven this spring and need some ideas.

I didn't spay it down, but it was only 50 degrees out or so and no wind.  I thought it would dry nice and slow in that environment.  Maybe not.?.

From the pictures it looks like you have a cmu post in the center of the hearth and a little less than a 4' span from wall to wall.  You kept the water/cement ratio low and you have a decent amount of rebar in there.  If you didn't tie the post into the slab with bars, and if you want to be really anal about the project, bolt some angle iron below the slab  from wall to wall and to the post.  If you want to get rid of the shrinkage cracks, mix up cement, fine sand and a little water  and rub it into the concrete.  You're going to cover the whole thing with fire bricks, right?  Overall the project looks great.

If it were me....I would continue on with the firebrick.

Will the bricks be going all the way to the edge of concrete shelf where the blocks are underneath?  If so, the bricks will be putting their weight on just the edge of the concrete and the blocks underneath.  If that's the case you're probably good to go.  You're probably good to go either way though.

It looks like the cracks are where the rebar is placed.

I noticed that too.  I measured the bar the to of the highest pieces was at 2" so I figured 1.5" was enough coverage.

The free span is right at 24".  I think I will end up doing something like that with some angle.  

How many days should I leave the bottom form under there before ripping it all out?  I suppose I could take the sides off today, but it don't know about the plywood used to hold the floor up till it gets hard.

Leave the forms in for a week and keep the concrete wet for a month if possible.  Now that it has set, the concrete can be hosed off every day and covered with plastic.  Better yet, cover the concrete with towels, wet them down, and cover that with plastic.  Most of the curing occurs in the first 30 days.

http://www.fornobravo.com/forum/



it's the arfcom of brick oven pizzarias


 

Did you pour a footer abound the slab perimeter, or did you just pour a flat 3-1/2" slab?

Doc_Zox is  the 411.... Just sayin..

I have been a member there for some time.  Not a lot of traffic though.  I did get some use out of it for finding ceramic board and what not.  

Some of those builds are wildly nice.

Just a slab.   I thought of pouring it thicker, but I stuffed a bunch of rebar in it and called it good.  It was probably 4-5 inches at the front, the back is resting on the wall footers.

James May's 'Man Lab' will be checking in shortly.

You should be ok.  

When the concrete was placed did you keep working it with the trowel or did you let it set until the surface water was nearly gone?

Minimum 2" of coverage for slabs. For a 3.5" pour I would have went with a WWF.

7 Days.

I work in concrete testing and building inspection every day. Those are most definitely shrinkage cracks. How accurate were you in the mixing of the concrete? Did you follow the instructions or did you purchase the concrete from a supplier and have it delivered? If the water/cement ratio was not closely monitored, that is what I can most assuredly caused the cracks. as other have said properly curing the concrete would have help ALOT especially in the first 24 hours, wet burlap sacks over the concrete in conjunction with a soaker hose would have been my route especially with a free span like that and a single mat of rebar.

   Was the hearth kinda of a free form design from your head or is that from an engineered drawing? Welded wire fabric or a double mat seems more sensible in this application but I'm not an engineer either. With the addition of fire brick and mortar and decorative brick on that there is still ALOT of weight that needs to be supported, I'b be weary. I've had guys rip out footings for small storage sheds for lesser cracks if that means anything. I would demo and repour with a fiber reinforced concrete from a supplier and cure it right with some propper supports.

Will

I'm going to buy some rectangular tube tomorrow and build a frame underneath it where the dome sits.  Then the concrete will have a minimal span.  If that doesn't work then this will be a thread with a reticle in about six months "part two...."

Should be fine, looks like it sagged because the under form was weak

Took the forms off today.  Next installment will be in April when I get a few days off work.

It seems to be fine, I had my wife walk around on it as a very official test. No honeycomb get anywhere.  I am still going to build a small support frame under it probably.

When the oven is done I will epoxy it or seal the cracks somehow to keep water off the rebar directly.  The site edges you see are duct tape I used to seal the form so it wouldn't bleed down the sides.

This is just a bump so the thread doesn't die before I get another update out.

If you are seriously concerned, take it out and do it again.  It's as simple as that.

If you do it again, you can take some of the suggestions given by others - welded mat, more rebar, wet burlap and plastic,...

With only a 2' span you could have almost used a 2x4 on edge for the foundation, depending on oven size and placement. Figure out the load per foot of oven wall on the first course, and you can see if there is even a slight issue. 1000 lbs distributed over 15' of wall is only 70 some pounds per foot, less than the weight your wife put on it walking around. Properly built it will also help support itself, so if a couple feet of foundation were kicked out, it would still likely be fine.

I wouldn't sweat the shrinkage cracks unless I was loading the center of the span heavily, like with more than a couple hundred pounds dead center of the span, and even then it would likely be fine. Worst case scenario is that it would sag slightly, it wouldn't go anywhere with all the rebar in it.

Thread was getting near the last page...  How is the project coming along w33b8t1?

The wife and I relaxed last night and watched an episode of "the best pizza I ever had".  All of those were cooked in a wood fired oven

My work schedule sucks.  No progress just yet.  I got side tracked with landscaping.  I am hoping to get going here in a few weeks.  

Thanks for bumping the thread.

Well goddammit, get going.  I hope to build something like that in the next few months, and I'd like to learn from your fuckup's

Got slammed here with Spring tasks too.

Glad you're willing to keep the thread going, it's a cool project.