Beginning to plan my build...

[inSaNE iRIsH]

Hey all, I'd like to start to plan my WFO build.  The build itself will likely not start for at least a year, but I want and need to put my plan together so that I can start slowly acquiring the supplies I will need to build it.  The only real decisions I have made at this point is that it will be a flat/low dome design and will be built on a cart for mobility.

One of the first real decisions I need to make for the design process is what size oven to build.  This will be my first (and hopefully only and last) WFO, so I want to make certain it will meet my needs.  I will not only use this for our family pizzas, but of course for pizza parties at our house, and I also hope to do some "events" with it (some for money and some for charity).  Based on these goals, I expect that I will need/want to bake multiple pizzas at a time in the oven but still be reasonable to just bake one at a time.  

I'm wondering how many pizzas a professional Neapolitan shop would bake in an oven at a single time?  I have to believe that when you are talking about cooking pizzas in 60-90 seconds, there is a practical limit to how many pizzas can realistically be managed in a single oven at a time regardless of how big you make it.  I am thinking that one person (in particular me) dedicated only to tending the oven could probably manage 2 possibly 3 pizzas in the oven at a time (provided of course there were others responsible for "feeding" me the prepared pizzas).  Even 3 seems like it would be challenging and really keep you hopping always needing one placed, rotated, or removed at any given moment, but with experience and practice, it is probably possible.

Does that sound reasonable to you all out there who have actual experience in this area?  If so, that leads back to the original question, what size oven is necessary to bake 2 pizzas at a time (pizza size <=14")?  What about 3 pizzas at a time?  I know I could simply draw out some dimensional circles and figure it out mathematically, but to allow for proper heat distribution for even cooking I don't want to be crowding the fire to accomplish multiple pizzas, and if the pizzas are all crowded too close together that would make it difficult to manage as well.  So I'm looking for wisdom from those with actual experience in managing a WFO with multiple pizzas in the oven at the same time.  How much space is realistically needed?  Would this same size oven not be ridiculous to fire up for a single pizza?  Would it consume drastically more fuel (wood) than an oven designed only for a single pizza at a time?

Secondly, in regards to thermal mass, heat up time, and heat retention.  Ideally, I would like to be up to cooking temps 800-1000 (right?) in an hour or less to allow for weekday cooks.  I would also want to be able to retain enough heat to bake bread and/or do some low-&-slow roasting over following day or two (this would also help in shortening the heat-up for pizzas again within this timeframe, right?).  I hope these two goals are realistic and aren't mutually exclusive, but once again I'm looking for your wisdom on these matters.  How thick should my walls be?  One-half firebrick (4.5")?  More?  Less?  How much insulation will I need (under the floor and on the outside)?  What else needs to be considered in these matters?

Lastly, especially for those who have built (or have knowledge about building) a low/flat dome oven, I know there will be a lot of outward pressure on the walls with this type of design.  How can this be dealt with?  What type of reinforcing and/or support is necessary?  What are the preferred/recommended/best ways to accomplish this?

I will greatly appreciate any and all input in these matters.  I have been thinking about doing a build for a LONG time (several years) but don't have a lot of money to spend at one time and don't have a lot of skills in this area.  So I will be scouring for deals on the building supplies I need and will be spreading out the purchases over at least the next year.  During that same time I will be endeavoring to learn as much as I can about that actual building procedures and hopefully with a good plan put together with all your help I will be able to do something previously impossible for me...build something that is functional, enduring, and aesthetically pleasing  .

Thanks guys.

[Tscarborough]

Is this a mobile oven?

[inSaNE iRIsH]

Is this a mobile oven?

I will build it on a cart (or perhaps I should say platform) with wheels for mobility, but it will not be a true mobile oven in the sense of being built onto a trailer.  For events I will load the oven (on the cart) into a separate trailer and haul it to the location and unload it for the event.  The only limitations this puts on my design criteria will be that I be able to easily remove the chimney for transport and the overall diameter can't be wider than can fit on a standard trailer (and if I use an enclosed trailer that the height with the chimney removed be less than the interior height of the trailer).

[Tscarborough]

With that in mind, you are going to have to compromise one way or the other on what you build.  An oven that is easy to fire and cook a pizza or 2 after work is not going to be able to perform well for commercial or event usage.

A WFO is a discrete thermal mass, heavily insulated.

To be able to fire it for an hour and reach clearing stage, you will have to have a very small thermal mass, something like a cast refractory oven with a wall thickness of 1-1/2 to 2" and a diameter of 32-36".

To be able to cook multiple pizzas for an extended period of time, you will want 4-1/2 to 6" of mass, something like 1/2 firebrick with an inch of cladding,  and it will require 3-4 hours of pre-heating for an extended bake as for an event. Minimum size probably 42" up to a 48".


Hopefully that will help you decide which type and size will work best for you.

[inSaNE iRIsH]

With that in mind, you are going to have to compromise one way or the other on what you build.  An oven that is easy to fire and cook a pizza or 2 after work is not going to be able to perform well for commercial or event usage.

A WFO is a discrete thermal mass, heavily insulated.

To be able to fire it for an hour and reach clearing stage, you will have to have a very small thermal mass, something like a cast refractory oven with a wall thickness of 1-1/2 to 2" and a diameter of 32-36".

To be able to cook multiple pizzas for an extended period of time, you will want 4-1/2 to 6" of mass, something like 1/2 firebrick with an inch of cladding,  and it will require 3-4 hours of pre-heating for an extended bake as for an event. Minimum size probably 42" up to a 48".

Hopefully that will help you decide which type and size will work best for you.

Really!?!?  Wow, I never thought the two would be that disparate in design criteria.  What do you mean by "... an inch of cladding..."?  What is the cladding?  Is it insulation or thermal mass?  What kind of material?

I didn't realize that all these builds I've seen using 1/2 firebrick walls took 3-4 hours to preheat.  How do people manage to eat homemade WFO pizza at a reasonable hour (say by ~7pm) during the week?  Or don't they?  If the oven was fired two nights in a row, how much would that preheat be shortened the second night?

[shuboyje]

My first oven was 30" with a sailor course(2.25" thermal mass instead of 4.5") and Bricks cut in thirds(3" thermal mass) for the dome.  I could get that oven to 1000F on the hearth and totally clear in about an hour.  I personally think that a 36" oven built that way would come close to all your goals.  You could do 2 pies at a time, probably heat it up in about an hour an a half once it's nice and dry, and still have enough mass for a batch of bread or some roasting. 

If you plan to trailer the oven multiple times, I would personally go way overboard with reinforcement.  I'd put in a steel harness, a fairly dense layer of perlcrete and a strongly reinforced layer of stucco on the outside to hold it all in.

[Tscarborough]

If you have it insulated well, and give it a good heatsoak the first night, it will be 4-500 degrees the next day.

[inSaNE iRIsH]

My first oven was 30" with a sailor course(2.25" thermal mass instead of 4.5") and Bricks cut in thirds(3" thermal mass) for the dome.  I could get that oven to 1000F on the hearth and totally clear in about an hour.  I personally think that a 36" oven built that way would come close to all your goals.  You could do 2 pies at a time, probably heat it up in about an hour an a half once it's nice and dry, and still have enough mass for a batch of bread or some roasting.  

If you plan to trailer the oven multiple times, I would personally go way overboard with reinforcement.  I'd put in a steel harness, a fairly dense layer of perlcrete and a strongly reinforced layer of stucco on the outside to hold it all in.

Jeff, You don't think 2-14" pizzas would be crowding the fire or each other in a 36"?  Your current oven is a 42" with 4.5" thickness, correct?  How long does it take you to preheat?  How many pizzas can you comfortably cook at once without crowding the fire or each other?

Would your old one hold enough heat the next day for bread/roasting or would it have to be in a shorter time frame?  Is this based more on insulation than thermal mass?

[inSaNE iRIsH]

If you have it insulated well, and give it a good heatsoak the first night, it will be 4-500 degrees the next day.

the next day morning (i.e. 12-14 hours later) or the next day evening (i.e. 20-22 hours later)?  assuming the latter, that should roughly cut the preheat in half on the second evening, right?

[Tscarborough]

The next evening, and it more than cuts it in half.

[inSaNE iRIsH]

The next evening, and it more than cuts it in half.

Ok, that is good to know.