Intro from New Hampshire

[Stray Catalyst]

I've been interested in WFOs since I tried out an earth oven built at a friend's farm - it lasted until the tarp blew away during a rainstorm, and it collapsed due to the rain. It took a long time to heat, had a poor draft, but the food out of it was wonderful! I've cooked several meals with it while it was intact.
My original idea was a non-mortared barrel vault, but now that I've read the Pompeii plans, I'm going to try a round oven in my back yard, and if it works as well as I hope, I'll build a slightly more elaborate one at the farm. The first one I'm building will be part of an outdoor kitchen / patio area we're building, so it's likely to get used a dozen times a summer or so, with occasional uses throughout the year. I'll be building it as cheaply as I can, using red clay bricks that I already have on hand for the dome, and buying the firebrick for the cooking surface (if my other ideas aren't going to work, see the questions). The enclosure will be a stucco igloo with 4-6" of vermiculite or perlite for insulation. The slab will be 4" of reinforced concrete, with FB insulation under the cooking surface, and I'll fabricate a metal door with insulation, probably more vermiculite or FB if there's enough left over. I have a few questions:

I have access to marble counter cutoffs, as many as I need, for free. If I decide to use one for the cooking surface, will it survive? I'm planning to have it "floating" as opposed to building the dome on top of it, in case it doesn't last, and I'll build it up to the same height as the bricks so I can replace it with bricks if I need to.

I'm fairly good with a tile saw, and have free access to a 10" wet saw as long as I fab a new top for it, as the current one is too small for bricks. I can also set up an angle table with clamps, so I can get the bricks cut to the same shape and angle. Would it make sense to shape them to minimize mortar, or am I just adding work for no real gain? Remember that the bricks are free, but the mortar isn't, and I'm trying to do this project on a shoestring budget.


Stray

[oventhusiast]

Re: Intro from New Hampshire

Please read before you start to build your dome!
Your pizza may get a bit crunchy! (with pieces of red brick in there!)
I'd hate to see you end up with an oven that is unusable.
Best of luck on your build!
Rick
Red clay brick. This is the traditional red clay brick that you find at Home Depot and at masonry supply stores. Clay bricks are made from clay, and fired in a kiln. They are typically made from local clay, as shipping is too expensive, and fired to between 2000F - 3000F (high enough to fuse the minerals). You can use clay brick in the oven dome, but we would not recommend using them in the oven floor. There are trade-offs to consider.

There are two shortcoming to using a clay brick in your oven dome. First, thermal cycling will cause clay brick to spall, where little pieces of the brick flake off, and could cause individual clay bricks to crack. It has happened to us. Second, clay brick is not as good a conductor as fire brick and as a result will take longer to heat up.

Still, you can find clay bricks for about $.50 at Home Depot, which make them the most cost-effective option.

Our view is that unless cost is a prohibiting factor, we would recommend firebrick. For example, a 42" oven some has roughly 180 bricks in the dome, so the difference in brick cost should be around $100. In the context of the overall cost of the oven, and large amount of human capital you will be investing in your oven, we think the extra cost of worth it.

If your choice is to build your oven with clay brick or not at all, we would strongly recommend building your oven with clay brick.

Red clay bricks are typically used for building the decorative arch and optional sides around the oven vent and vent landing, and can be used for any decorative feature.

[dmun]

Re: Intro from New Hampshire

I have access to marble counter cutoffs, as many as I need, for free. If I decide to use one for the cooking surface, will it survive?

No. Marble or granite simply will not withstand heat. They will crack and chip. The only natural stone that's suitable for a cooking surface is soapstone.

Would it make sense to shape them to minimize mortar, or am I just adding work for no real gain?

It makes no sense. Labor, in any real sense, isn't free. Diamond blades certainly aren't free. If you want, as an exercise in craftsmanship, to build a perfect fit dome, at least start with the correct raw materials. A red brick dome doesn't call for anything more than a slathering of homebrew mortar.

[Stray Catalyst]

Re: Intro from New Hampshire

Thank you for the input, and for saving me the wasted effort to use the marble. I'll skip the marble and the excessive sawing. I'm still gathering materials and money, I'll post pictures (and further questions) when I have them.

Stray

[Stray Catalyst]

Re: Intro from New Hampshire

I've been shopping around for materials, and trying to figure out if I can afford to build this. I've seen precast concrete footings being sold for considerably less than it will cost me to rent a mixer. As I'm a welder, I'm planning to make the stand out of welded metal as opposed to cinderblocks, so I'll need footings in any case. Are the precast ones good enough for this, assuming a footprint large enough to handle the weight (I'm guessing about two to three tons) with my soil conditions? Or should I build forms, tie rebar, etc? I'm not going to cut corners on the slab, or the cooking surface, but if I can save a few hundred dollars in cement and block, it could make the difference between building this oven, or going without.


Stray

[dmun]

Re: Intro from New Hampshire

We've had a discussion about these before. I can't find a link to it at the moment. They weigh about 60 pounds, right, and are made to take a PT 4 x 4? I don't think anyone has used these for a build yet. Let us know how it works out.