48" ? Pompeii... Early Stages

[djginivisian]

This will be a multi-use oven for pizza, bread, roasting, baking etc..located in Massachusetts

The corner installation foundation is complete and the cinder blocks are about to be set for the base. I was prepared to build a 42" but now have access to 4.5x9x3.5" 'arc' shaped bricks which, when joined, produce a perfect circle with a 48" interior.

This first course would sit atop standard size firebrick (oven floor)set on it's narrow side. The perimeter will be topped by 'tapered' half bricks which, when stacked, will form the dome and require minimal mortar.

1. What are the pros/cons to going up to 48"?

2. What would be the optimum interior height? One course of the 'arc' bricks topped with the 'tapered' 1/2 bricks will provide a 21" height. I could increase the height by adding a second/third course of the 'arc bricks.

3. The foundation was intended for a 42", how far can I cantilever the hearth/counertop beyond the cinder block oven stand?

4. What should the height and depth of the door/oven opening?

5. The Hearth: I am considering an isolated hearth for more thermal mass. Is a layer of firebrick set below the oven floor acceptable or too thick? Is this unneccessary if I am laying the oven floor brick on its narrow end? Or is it best to pour a ring of refractory concrete? And when does FB board come into play?

6. Has anyone used foam glass as a floor insulator?

All comments/questions/answers appreciated. DJG

[Gulf]

Re: 48" ? Pompeii... Early Stages

That perfect 48" circle, only works for one course. You really need to ask yourself, if you will need that much room for very large cooks on a regular basis. You will also need think about wood availabilty. A 42" oven will hold a lot of dishes at one time .

That out of the way, you are only increasing the oven's OD by 3" (front back and sides). If your stand size is correct for a 42", then a 2x4 width (all around) would add more than enough. If you are wanting to add the full distance to the front of your stand a, 2X6 should be close enough. You can cantilever a properly reinforced slab, of the correct thickness, a lot further than you will need to make the 48" fit.

[boerwarrior]

Re: 48" ? Pompeii... Early Stages

1) That will be a huge oven! The cons are that you will need a lot of wood to heat it up. If you really need an oven that big then go for it.
6) If you are going to build an oven that size, you really want excellent insulation. Go with a proven good insulation system like Calcium Silicate Insulation Board for the floor and Ceramic Fiber blanket for the dome. I don't think it is worth experimenting with new insulation techniques on an oven that size

Neil

[UtahBeehiver]

Re: 48" ? Pompeii... Early Stages

Ditto on size and fuel usage. That is a big oven, mine is a 42" ID and bigger than anything I need it for. No matter what the brick size and shape, you will need to make some adjustments. I used tapered bricks like your pic showed.

I used a combination of 2" of FoamGlas topped with 1.5" of ThermoGold 12 CaSi. Used FoamGlas on the bottom since it will not absorb water. It is a little brittle to work with. You can see details on my picassa album on my thread.

Door opening height is a function of dome height. Not sure what you mean by door depth (width?) Lot of thread on this.

[deejayoh]

Re: 48" ? Pompeii... Early Stages

+1 on "that's a big oven"

You're paying more for the shaped bricks, and you're going to pay even more for wood. Plus you're setting your floor on the narrow edge which is going to further increase heat up time and wood usage.

The size/configuration you're talking about would be suitable for commercial purposes or feeding a large Amish family as the only cooking appliance.

If your needs are somewhat less than that, I might look at building a smaller oven with less mass in the floor.

As others have pointed out, you'll quickly lose the convenience of those bricks making an easy circle and have to cut them or deal with gaps. And it's going to be more of a mental puzzle to cut shaped bricks than it is square ones, as you have to adjust each cut for the existing angle.

[v12spirit]

Re: 48" ? Pompeii... Early Stages

2. What would be the optimum interior height? One course of the 'arc' bricks topped with the 'tapered' 1/2 bricks will provide a 21" height. I could increase the height by adding a second/third course of the 'arc bricks.

The interior height can be as much as 1/2 ID. That makes sense because most ovens are built using the IT. However, some designs lower the dome to make the oven better for pizza making so that no need to "dome" your pizza. IMHO, your oven's big size will prefer lowering the dome a little bit. or you may have a pizza cooking faster on the bottom. 21" is not bad IMO.
BTW, are you going to use the IT to build the dome?

3. The foundation was intended for a 42", how far can I cantilever the hearth/counertop beyond the cinder block oven stand?

Do you have to? Why don't you go with the intended foundation? I think 42" is pretty spacious for home use.

4. What should the height and depth of the door/oven opening?

The opening height should satisfy the golden ratio which 62.5% of the internal height of the dome.
I was frequently told that there are no limits on opening width, but I strongly believe that it is better not to exceed 1/2 ID. That makes your oven more fuel efficient.