Building or sourcing a pizza oven can have many questions. One of them is about the unique domed shape of the pizza oven. Is this for a reason or is it just tradition?
Can pizza ovens be square?
Pizza ovens can be square or rectangular, with an arched roof, but it is less common. A domed pizza oven has better heat efficiency from evenly reflected heat and better hot air flow. This gives a hotter oven with less cool spots.
This article has a delve into how pizza ovens work, and why the dome is the best design. If you are ready to buy then check out my pizza oven buyers guide for everything you need to know before you purchase.
Why Most Pizza Ovens Are Domed
How Heat Works In a Pizza Oven
There are three different kinds of heat in the oven which happen simultaneously to cook the pizza.
Convection is the movement of hot air around the oven. Cool air enters the front, heats up and circulates around the oven chamber. Convection is replicated in home ovens by a fan to circulate the air, in a pizza oven this happens naturally. It creates a more constant temperature.
The convection cooking process cooks food evenly because any hot or cool air pockets are eliminated due to continuously circulating air.
This is heat that is reflected back down to the food. The walls of the oven are heated by the fire, this gets stored in the brick and then radiated back. This is why you can cook in a pizza oven without a fire – that energy that has built up in the bricks earlier is now used for the cooking. If you have better radiation, then you are going to have higher cooking temperatures.
Conduction is the transfer of heat from a hotter surface to a colder surface from contact. In a pizza oven this happens on the oven floor when the raw dough is placed upon the hot brick.
This is the secret to crisp pizza bases and thoroughly cooked dough – you need that boost from the bottom up. This works in all shaped pizza ovens, given that the floor is hot enough. This method is mimicked in a home oven with a pizza stone that has been preheated.
Benefits Of A Domed Oven
When a pizza oven is round, it has a spherical dome. When an oven is rectangular then it can’t be domed so its roof is a tunnel shape called a barrel vault. The barrel vault is less effective with heat.
Better Radiation, Convection and Conduction
The dome shape reflects heat back to the pizza from all angles, so this produces better radiant heat than a barrel shaped ceiling. Convection flow happens more efficiently in a dome oven. You can watch smoke spin around the dome and not spill out of the entrance. This comes from the dome shape, the entrance at a specific height and the chimney in a specific place. Because of better radiant heat, the oven floor is hotter. This means that the resulting conduction cooking will be better too.
Less Materials, Less Mass
It’s worth mentioning that a domed oven is lighter on materials. This is due to its stronger structure – every brick supports the center of the dome. With less bricks and concrete comes less mass to heat up. It doesn’t necessarily mean less insulation because that comes from high insulation materials like a ceramic fiber blanket or vermiculite.
It Gets To Higher Temperatures
Because the oven is more efficient with convection and radiation, you can get up to higher temperatures easily, and hold that temperature. Also, the extra mass of a rectangular oven means the heat must permeate through to all that mass, and is constantly drawing the heat energy away from the central oven.
High temperatures are really key to the best wood fired pizzas. If the temperature drops slightly then the pizza takes a couple of minutes to cook, rather than 60-90 seconds and the outcome is pretty different. For the best Neapolitan style pizzas you need temperatures around 900F/482C. In fact the AVPN regulations for Naples pizza strictly states at least 905F/485C to be named a true Neapolitan pizza (the PDF regulations can be found here).
It Heats Up Faster
The better heating qualities and less mass means that the oven can get to cooking temperatures faster. This is a big win because pizza ovens can sometimes take hours to heat. If it takes too long to heat up then you might use the oven less.
The Fire Is In A Better Place
Barrel vault ovens are often longer than they are wide. This narrow shape with extra length is a bit pointless because the space isn’t efficient for cooking pizza. There isn’t a good place for the fire to go. If the fire is on the side and near the front, then there is space for one pizza next to it and then a cold spot at the back (which is hard to get to!). If the fire is in the back corner, then the adjacent back corner which is red hot is difficult to access and the front has a cold spot.
Round pizza ovens are equal in width and length. With a fire on the side, there is space for pizza near the back as its not too far away, and on the other side of the fire. So you can cook more pizzas easily around the fire, as the fire is more tucked away to the side.
Barrel Vault Shape Benefits
Barrel vaults are more traditional for bread ovens. The shape suits bread better than pizza – just think of the shape of a bread loaf and the shape of a barrel vault tunnel. You can fit more bread into a barrel vault oven, so that’s why they are historically more common for bread. These days, the average baker probably isn’t going to fill their oven with bread so its not necessary for most.
The barrel vault is easier to clean. It has a larger opening which makes getting inside with a brush easier. The rectangular shape means tools like brushes and shovels are easier to use to clean out the ashes.
Some may think the barrel vault has better aesthetics so you might choose it based off this. This means you will sacrifice performance for looks unfortunately. Remember that you can still build an enclosure which can be any shape you want.
The Enclosure Can Still Be Square
Remember that just because the cooking chamber is domed, that doesn’t mean the enclosure has to be too. Typically, ovens are rendered and painted to withstand the elements. But some really aesthetically pleasing builds can be completed with a roof and brick casing. This insulates it even more, and you don’t need fire bricks for this outer layer as it has an air gap between the oven.
Other Important Things To Consider
Door Height Ratio
There is an optimum height to use for the entrance to ensure that the oven can retain the most amount of heat, but can still draw enough air to fuel the fire. This is somewhere between 60-70% of the oven roof height. This article goes into detail of the science behind this, with some illustrations.
Materials To Use
Insulation is an important factor. You can use calcium silicate boards for under the oven and ceramic fiber blanket or vermiculite to insulate the walls. Firebricks are more expensive but they resist higher temperature so won’t crumble.
If you want to know more about the cost, then see my article on how much does a pizza oven cost.
Size can dictate how many pizzas you can fit into the oven. You need an oven about 32″ to fit 2 large pizzas inside. With this size oven you can serve a pizza every minute or so, so it’s not that important to go larger than this. Cooking more than 2 pizzas at once can also be difficult to pull off.
How Many Bricks?
A poll looked at how many bricks people used to build their oven, which you can see here. The number is in the range of 200-250 bricks needed.
Building A Domed Brick Oven
Here is a great time lapse of a guy who made a pizza oven in 20 days that you must watch. You can get a detailed view of everything that needs to be done. And then you can make a decision if you are up for the task!