Concerned About Rebar in Insulated Layer

[james]

Dave, if you wanted to, you could still put a layer of either vermiculite concrete or insulating board between your concrete slab and the brick cooking floor. I have a lot of hands-on experience with this (I've built and used two Scott ovens), and the problem with getting and keeping the floor hot is real. Something to think about.

You will enjoy your oven either way!
James

[DrakeRemoray]

Dave, I am glad you are excited about your build. The shape of the Scott oven will not be a problem, but that big slab/heat sink could be a problem. Take the advice here and go ahead and insulate on top of your slab now. You can still bake a ton of bread. I have attached a picture of a 25 lb bake in my pompeii. Plenty of heat retention with a floor of bricks on the flat side and insulation underneath. You just don't need that extra mass (the slab) for home use.
See these threads for proof:
http://www.fornobravo.com/forum/f30/...cord-6502.html (Temperatures - for the record)
http://www.fornobravo.com/forum/f25/...king-1134.html (3 days of cooking)

If you are worried about height, use the insulation board that Forno Bravo sells. If height is not an issue (and a higher oven is generally easier to work in, check the height of most professional pizza ovens) then just pour 4" of vermiculite concrete on top of the slab.

I started out planning to use the Scott design and changed my mind...see my thread here:
http://www.fornobravo.com/forum/f6/m...orado-472.html (From Mailbox to Pompeii in Colorado)

You are gonna love your oven!
Drake

[DaveDQ]

Thanks for the replies. As I read this, I'm a bit upset with putting up that slab. The main reason I went with it was because I was worried about the structure, and though having that would hold up the actual oven better. I have this anxious fear that everything is going to collapse.

I will consider the insulating boards and then surround it with vermiculite. One question, when you say lay the bricks flat face, is this also done to retain heat better? I'm sure most of you have seen that his ovens have the upright bricks.

[Jed]

Hey Dave,

The 'which way to place the floor bricks' question is one we all address. An American mantra is 'more is better', so we are drawn to the idea that standing the floor brick on the short side, will be the better solution.

Again, it is a builders choice question.

If you stand the brick on the short edge, the thickness of the cooking floor is now about 4 inches thick. If you set the brick on the wide side, the thickness of the floor is about 2 inches. The difference, in this application, is thermal mass. The thicker floor will take longer to heat, and it will hold more heat allowing for longer cooks.

Experience has shown that for the regular back yard cook, the 2 inch thick floor is good enough; it provides 'enough' thermal mass; that the 'more is better' mantra does not always produce the best solution to the problem....

Like I say, it is a builder choice.

Keep up the good work! It is always easier to improve results before the bricks are installed, so you are doing the right thing by asking questions!

JED

[roobqn]

ok I am also in the planning phase and was going to use the Scott build, and find this thread interesting.

If the bricks are placed on their short side creating 4" floor would this not act as an insulation layer? Instead of vermiculite and 2" flat brick floor you would have 4 inches of firebrick.

Does the vermiculite have any heat retaining properties?

Good thing this forum is around, can avoid a lot of mistakes.

[DaveDQ]

I laid my hearth today and went with laying the bricks flat. These bricks were given to me, so I didn't have 114 to use. I used about half of that amount laying them flat.

[DrakeRemoray]

DaveDQ, I think you will be happy with that decision.

roobgn, The bricks act as mass, not insulation. The vermiculite concrete does not have heat retaining properties except that it acts as a barrier (insulation) to keep heat from escaping...The firebrick (or other mass like refractory cement) will retain heat.

Drake