Best dome diameter for a home forno.

[Travelinman]

I am back to Forno construction, after a medical delay.
i am ready to start actual dome and have a question or two.
I had planned on a 42" dome, but now am thinking that might be o overkill.
I already have most of the materials, so material cost is not an issue.
The cinder block support is built and the base has two inches of vineculite concrete with two inches of CaSi on top.
So, the question:..
is 42" too large for a small family?
I plan to use for pizza and bread, but also want to cook meats like they do in Europe.
i ant to modify design to allow a removable steel great for broiling and brass bearings (bushings) to add a rotisserie at front side in the tunnel access.

So what size should I consider, before I start bricks.

Thanks.

[MarkJerling]

42" is fine, in my view, for most uses, but if you're only ever making a few pizzas, and one at a time, then you could consider a smaller oven. I enjoy the versatility of our 42" oven, but it is a big oven to heat for only 2-3 pizzas. It's, of course, very practical when I'm cooking for more people, but if it's just my wife and I, then I really need a smaller oven.

[UtahBeehiver]

Second Mark's comment.I have a 42" and there is just two of us so the oven only gets used for family and large parties. If I ever build another it will be smaller, ie 36" or so. Even David S with his micro cast oven can do breads, roast etc after in pizza fires.

[rsandler]

I've built two 36" ovens, and I don't see any reason I'd ever want a larger one (due respect to those who like their 42" ovens!). You can fit two pizzas next to the fire, which at least for me is the most I can manage anyway without burning something. For bread, I can fit up to 8 loaves at a time with the coals raked out the next day. On my current oven, I can get it hot enough for pizza in about an hour.

[david s]

The question about size relates primarily with mathematics. A 20% increase in floor diameter leads to a 44% increase in floor area and a massive 73% increase in volume. This also leads to a massive increase in materials, labour and cost as well as the requirement for a massive stand to support the weight increase.Fuel consumption is pretty much directly proportional to chamber volume so a vast amount of labour in carting, cutting and splitting wood can be saved by building a smaller oven. I have a policy of never buying wood because there's plenty around if you look. I use fallen sticks and small branches at the base of hardwood trees and rarely have to either cut or spit wood.

The American psyche that dictates bigger is better is well illustrated by the vehicles they prefer. Take the Dodge Ram, compared to the Italian Piaggio Ape utility trucks popular respectively in each country.

Most domestic oven owners usually cook only one pizza at time because they cook, at two minutes, faster than can be prepared by a single person. For commercial operators who provide individual pizzas for individual orders, a larger oven that can cook multiple pizzas is mandatory,, but for a home situation provided guests are encouraged to share whatever comes out of the oven, single pizzas coming out every two minutes is easily sufficient to cater for 60 guests in a couple of hours.Using this method a single operator can prepare, cook and cut, using guests to be the waiters ("Have a piece of this, share it around and bring me back the paddle")
In fact eating slowly this way, as Europeans do, people actually eat less because the body has a chance to tell the head that it's had sufficient.

[MarkJerling]

Well said David. I think, if I were to do it again, I'd go smaller. As it is, I have lots of wood, so it's not so much about volume of wood, but rather time. It takes a good 3 - 4 hours to heat my oven. It would have been nice is if was quicker.

[david s]

Yes, one of the drawbacks of brick ovens is that they require the full width of a brick (4”) for the structural integrity of the mortar joints. The thicker walls provide more thermal mass for extended heat storage, but require longer heating times which leads to greater fuel consumption. This is fine if you don’t mind the extra wood required or you particularly want extended cooking time.
Cast ovens by contrast can get away with 2” wall thickness for small ovens (usually 3” for big cast ovens), because of the elimination of mortar joints between small units. This reduces heat storage, but also fuel consumption and time taken to reach required temperature.
It just depends what you want from your oven. Most first time builders only find out, after they’ve built and used their ovens for around a year, what kind of oven they really require.

[Giovanni Rossi]

All good input so far. I really like my 42" oven and I've just started to learn about it. The large floor makes it really easy to keep the fire and coals at bay and have areas with different temps to work with. However, the wood and labor costs need to be considered. I'm fortunate to have amassed a huge wood supply over the years and time is not an issue. If I just want a few pizze I fall back on a fire brick + baking stone setup that I use to build a small "oven" in my gas grill. I've used that for years and it makes really good pizza.

What I would like to add is that whatever size of oven you build, one thing to consider is the size of the opening. It needs to accommodate the cooking vessels you want to use. My opening is 19.75" and allows me to use commercial sized sheet pans. Also, as others on this Forum have cautioned, too narrow of an opening or too deep of an entryway can hinder working the useful floor space.

[Travelinman]

I am sorry that i am so late in responses.

I really appreciate the info. Great responses!

I am still trying to decide about the 36" vs. 42". It will mainly be used for myself and my wife, so the 36" might make sense. Faster pre- heat. Less wood fuel versus size of floor.
Two questions more.

Since i built the insulated floor base for a 42", will this cause any problems with a smaller footprint.? The current base is approximately 50" no floor brick yet.

Does the size of the opening effect heating in relation to oven size? If I reduce size and the opening is the same, will it effect heat distribution or function.?