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ubarch 06-24-2010 04:36 PM

Some question before I make my stand permanent
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I've been meaning to build an oven for quite some time, and I've finally started. Attached are pictures of the cinderblock stand that I've arranged. This weekend I plan to start with some irreversible portions of the building process, and I wanted to ask some questions before I make anything permanent.

1.) Home Depot being what it is, the palette of blocks that I purchased turned out to be made from what looks like two different molds, each with a slightly different length. To get things to line up properly, I've had to chisel the flanges off of a couple of the blocks to shorten them (you can see one in the picture of the void that is attached). The blocks I did this to seem to have come through alright, but could I have damaged them?

2.) Due to the varying cinderblock shapes, the voids that Forno Bravo instructs you to fill with cement are not lined up (picture below). They still seem to make a cohesive chamber. Is this OK?

3.) How important is it that the fourth course of cinderblocks be level? It doesn't seem very important (since it will be covered by the hearth), but I want to make sure before I pour cement into the voids.

4.) My local Home Depot does not carry 8x8 blocks, so I've been cracking 8x16's in two. Pictures below is one mistake I made. It's at the base of the stand, facing the inside of the chamber (so it won't be in sight when the oven is finished). Should I let this slide, or is it a structural issue?

5.) Finally, I was quoted well over $100 for a length of 2"x2"x3/8" angle iron. Venerated sirs, I submit to you that this pricing is balls lame. I was thinking about casting an archway to bridge the opening in the stand instead of using the angle iron approach, and I was thinking of doing it by making a more sophisticated mold for the hearth than what's in the FB instructions. In a nutshell, I would lay out all the cinderblocks I could, fill the voids with cement, and then construct a mold that encloses the hearth area and also a lintel over the opening (all of it reinforced with rebar). Is this s sane plan? Have other people done it?

Thanks for any advice you can offer!

GianniFocaccia 06-25-2010 09:48 AM

Re: Some question before I make my stand permanent
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As long as the blocks you 'modified' are not cracked, you're good to go. They don't have to line up perfectly, but make sure your rebar goes through the entire column. I used an angle grinder to cut my blocks cleanly.

Also, angle iron is not required to span your stand opening. As long as you form the support slab and place your rebar properly, it'll be plenty strong. Here's what I did.

fxpose 06-25-2010 10:30 AM

Re: Some question before I make my stand permanent
Ubarch.....Yeah, most of those imperfections, slight mis-alignments, and out of level blocks can be filled, touched up, or corrected as you go along.

GianniFocaccia....Your stand is looking great! I like the way you embedded the oven floor. Do you have a build thread?


Neil2 06-25-2010 10:53 AM

Re: Some question before I make my stand permanent
Your suspended slab will easily span your opening, just put an extra couple of 1/2 inch rebar across the span.

ubarch 06-25-2010 11:15 AM

Re: Some question before I make my stand permanent
That looks awesome, GianniFocaccia.

So you're saying that if I make sure to have a couple lengths of rebar in the section of the hearth that's unsupported, that it will be stable? Nice.

While I'm asking questions...

The simple structure to the left of the oven stand is intended to be a basic grill. The idea is to affix outcroppings to the inner surface so that two sections of expanded steel sheet can be placed there (one for coals, one for food bits). I wasn't sure if cinderblock can tolerate grill heat, so I was planning to put a layer of ordinary red bricks along the inside surface of the grill and use brick outcroppings to hold the grill and coal surfaces. However, if cinderblocks can take grill heat, then I might be able to get away with simply parging the inside surface, and installing stainless steel dowels into the walls to hold the sections.

Is it worth it to install the brick layer? I'd only do it if I had to, since it subtracts from the total area of the grill.

GianniFocaccia 06-26-2010 09:59 AM

Re: Some question before I make my stand permanent

Sure. Lots of builders have spanned their support slabs this way.

Unfortunately, the concrete blocks will not withstand the heat and over time will fail. One way you could do it would be to install 8x6x16" blocks on the two topmost courses. Just like the oven support slab, you could pour a 3" concrete grill 'floor'. You could place the ends of the rebar across the top of the uppermost 8x8x16" blocks and then build your form and pour. Then line the floor and grill sides with firebrick. I would also plan for a small vertical hole in the slab so water can drain out.

GianniFocaccia 06-26-2010 10:29 AM

Re: Some question before I make my stand permanent
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Thanks for the kind words. Yes, I have a build thread (OctoForno), but it hasn't gotten very far. You see, I got bit hard by the whole oven/outdoor kitchen thing and underestimated the time requirements to do the job all by myself. Never mind the fact that I've never done any real masonry before and 'modified' my original plans several times. The Minister of Finance (I love that term!) requested I do the landscaping before continuing on with the oven/kitchen. So to keep myself semi-engaged with the oven while I've put in the patio, I've slowly acquired refractory mortar, EPrante's graciously forwarded indispensable tool, The Angle-Izer and enough 3cm soapstone to cover a 42" floor and entryway. Oh, and I also got five different kinds of tomato plants (including San Marzanos) into the ground. Right now, I'm hoping I can begin working on the oven in July, right when it's the hottest.

Wish me luck!


fxpose 06-27-2010 12:17 AM

Re: Some question before I make my stand permanent
John....they're all part of the big picture. I can already picture your patio and outdoor kitchen area are going to be awesome.
Looking forward to your oven build....:)


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