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scarnucci 09-08-2011 06:59 PM

Preparing for steel oven build.
Hello Pizzaiolos,

Long time lurker here. Finally getting ready to venture into the build stage.

I have been assembling my materials for the better part of a year. This weekend I will take my angle grinder to a 40 inch propane tank end and cut off my dome. (Flushed it already, of course) I have a 4x6 dual axle trailer which I will be stripping down and having the frame built on. I scored a mess of firebricks on CL. Downside is I dont know their exact composition.

I have been in contact with a local welding school that searches for build projects to train their students on. I have no welding experience myself, so I am hoping I can explain my needs to their instructors well enough.

I have a couple of questions that I hope some of you can answer.

For the support of the oven, I hope to have a square "basin" built into the frame, and I will layer 1/2 inch plywood, forno bravo 2 inch insulating board, then the fire bricks. Is this adequate? I would prefer not to cast a floor.

Over the steel dome, can I get away with just forno bravo insulating blanket, then an outer shell? Or will it be terribly inefficient without a layer of thermal mass over the steel dome first?

Of course I've read the major steel oven build threads on here already, and many thanks to those who have gone before. Cost is definitely one of my concerns as I only have 2k budgeted for the rest of the build. That includes the materials and having the student welders do their thing. Am I kidding myself that I can get it done for that?

Wiley 09-09-2011 10:44 PM

Re: Preparing for steel oven build.

I think you will need the thermal mass.

Also, I have been communicating with another member in Texas who is building a similar WFO to what you are describing (save that he was not considering going without the thermal mass). He too was considering using a sheet of plywood as a base for the insulating board. I will give the same advice I offered to him and that is to consider using a thin sheet of steel instead, something like the steel forms which are used for elevated concrete floor pours. If those are unavailable then a reinforced sheet of 16 guage steel. Over the long haul of several years/decades the steel will be much more durable. If you were to have problems with the plywood the whole WFO would have to be disassembled.

I would think you should have no problem building your WFO for 2 grand...I built my WFO (which is different in that it is on a platform) for about $500. So if you have the tank end, bricks and the trailer you should be fine. With the extra money I would consider an additional inch (or two) of insulating board beneath the hearth bricks.

Hope this helps,

scarnucci 09-10-2011 10:43 AM

Re: Preparing for steel oven build.
Thanks for your input. The steel vs plywood does make sense for long term durability, and likely wont add much to the pricetag.

Regarding 4 inches of forno bravo board insulation under the hearth bricks. Does that board compress over time? Or will it remain at 4 inches for the long haul?

scarnucci 09-21-2011 08:32 AM

Re: Preparing for steel oven build.
Trailer went over to the welders on Monday.

Yesterday I placed my order for three sheets of Forno Bravo board...shipping sucks.

Inside the steel dome, and on top of the fire bricks I want a 3cm thick hearth of either soapstone or more fire brick.

I prefer a seamless 36.5 inch circle to fit inside my 37 inch dome.

An Indiana soapstone manufacturer wants $650 to fabricate the circle, or will sell me a 40''X40'' square which I have to cut to my desired shape for close to $500.

A Louisville refractory fire brick manufacturer said they can make me a same sized circle of firebrick for just over $300.

I was hoping to get the soapstone but the cost difference has me leaning towards having the fire brick made.

Any opinions?


scarnucci 09-21-2011 09:00 AM

Re: Preparing for steel oven build.
Another thought...

The plan I gave the welders was to create a 48"X48" tray to house the insulation board and bricks.

The fire bricks I have are 4.875"X8.25" which means I would have to buy a saw to cut the bricks to fit that size. Not the end of the world, though I could just have him fabricate the tray a few inches longer to fit whole bricks.

My math has it at 48.75"X49.5" for a 10X6 brick hearth

Downside with that is that the 3 sheets of 24"X36" FB board would leave me with a little gap around the edges. Could I fill that gap with sand?

scarnucci 09-30-2011 03:03 PM

Re: Preparing for steel oven build.
Back from the welders today with the first part of the project.

First, a couple of pics of the trailer.

scarnucci 09-30-2011 03:11 PM

Re: Preparing for steel oven build.
Here I have installed the FB board. The boards were not quite equal in size. One was a bit wider than 24"" and one was just under. Took a little trimming to fit into the 48" wide tray.

One FB board was also a little thicker than the others, so it is a bit uneven. Not the end of the world.

Ive got most of the bricks in, I'll have to cut one row. Wondering if I should stagger the whole thing or if I can just keep them as is. Dont have a brick saw, and am wondering if I should attack them with an angle grinder or bite the bullet and buy the saw.

Here is a reference on how the steel dome will fit. Dome is still at fabricators so this is a piece of extra that I threw onto just to have a look see.

When the dome is finished, this is where the oven door will be. I'm going to have to have a shelf made, because the door "tunnel" is going to extend out farther than this tray is right now.

Plan is to weld three thin metal bars from the dome at 90* to each other, left, back and right, and attach it to the frame. I am weighing the fact that they may act as heat sinks, heating up the frame, against the fact that the dome slid all over the trailer when I was driving it to the welder's shop. I need to have something keeping it in place, and it being on the road occasionally, I cant put all my faith in weight and gravity doing it all.

Dome should be done next week sometime.

Wiley 09-30-2011 04:15 PM

Re: Preparing for steel oven build.
The bricks cut like butter with a diamond disc on a cheapo Harbor Freight grinder. I bought one of the grinders for my WFO just to see how long it would last and because I didn't want to pass any more brick dust thru my Makita than I really had to. The grinders as so very inexpensive I figured they could not be built well enough to last long. Well the Harbor Freight grinder is still going strong, it's just as loose and noisy as when I first started it but it does what is asked of it. Diamond disc also came from Harbor Freight. Just remember the dust mask and eye protection and hearing protection... the bricks cut easily but not quietly.

A suggestion on your construction...Cut the interior bricks to fit inside the dome; however, the ones on the bottom should not extend all the way to the edge of the tray. Allow them to extend out so that they support the steel dome and the cladding but fill the rest of the space with vermicrete or perlcreate. This is to stop the outer bricks (beyond the cladding) from acting as heat sinks pulling heat from the oven.

Regarding the steel support bars for keeping the dome in place: I would suggest you think something along the lines of bars with holes drilled in them to lessen the x-section and thus heat transmission.

Have you given any thought to some triangulation/bracing on the support legs for the oven?

Otherwise looking good!


Neil2 10-01-2011 10:17 AM

Re: Preparing for steel oven build.
In looking at the pictures, I am wondering why the bottom brick layer covers the whole pan. If this is for thermal mass, I would only have the brick layers under the oven footprint itself.

The way you now have it, the lower brick layer will "wick" heat away.

With your design, you could both isolate and contain the finished oven and brickwork with a layer of verimcrete up to the top of the pan.

When you cut the brick, either with a saw or grinder, keep the dust down and extend the life of your cutting edge by soaking the bricks first.

scarnucci 10-01-2011 12:19 PM

Re: Preparing for steel oven build.
Thanks for your responses.

So, I'll cut back on some of the brick layer, and fill in with vermicrete.

If I wanted to sink 3 anchors in the vermicrete layer, and weld the support bars to the anchors, would the vermicrete have enough strength to hold the anchors in place?

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