The first question you’ll need to answer, after you’ve decided to build a refractory pizza oven—either a precast oven kit, a cast in place oven kit, a pre-cut brick oven kit, and a Pompeii oven—is how big? And answering that basic question can be a real challenge.

Too big, and you’ll regret the amount of time it takes to fire your oven, and how much wood and effort it takes getting it hot and keeping it hot. You might find yourself not using it as much as you had hoped, because the whole process of using it was more than you had expected. Too small, and you will forever regret not having those last four inches of space, maybe for more pizzas at at time, and more likely wishing you could put more and larger roasting pans and cast iron pans in the oven at the same time. Thanksgiving lunch in a wood-fired oven awaits!

Let’s make things a little bit more simple by breaking cast ovens into three basic sizes. Using the scale that includes very small portable ovens (12-16″) and small countertop ovens (16-20″), refractory ovens start at mid-size (24-28″) and come in large (32-36″) and XL (40-44″).

It’s important to note that cast in place ovens are different than steel ovens and precast refractory oven kits, where the prices go up and up, and then eventually explode as the ovens get larger and larger. And while it’s true that material costs do go up as ovens get bigger, the lion’s share of that big price jump is labor (welding and casting) and shipping. Don’t forget that shipping metal ovens isn’t free, it’s just built into the cost of the oven, and shipping larger ovens costs a lot more as the plywood crates get bigger and bigger.

While the cost of materials that goes into making a pizza oven does go up as the oven gets larger, it doesn’t go up by that much. If you are considering building a cast in place oven and you’ve look at prices and compared the price of the different sizes and the cost of similarly sized precast ovens, you’ll quickly notice that the price jumps from one size to the next is not that great. Typically just $100 to move up to a larger oven. Of course you will also not that the cost of a cast in place oven is a fraction the cost of a precast oven.

Also, the materials to build a cast in placer oven come in bags, boxes, or are loose, where each piece can be easily picked up by one person—regardless of how large your final oven is. The pieces of a precast oven kit also tend to get heavier as the oven gets larger.

All of which means that if you have the space for a larger oven, you should seriously consider building a larger oven.

By analyzing the three different classes of oven—mid-size, large and XL, you should be able roughly gauge which size oven is right for you. If you have a small family, don’t throw larger parties, want to use your oven a lot and really care about how quickly it heats up, you might be interested in a mid-size oven. That narrows your choice down to 24-28″, and possibly 32″. Unless you don’t have the physical space for a 28″ oven, you should opt for the 28″ oven. It does a lot more than an 24″ oven and the cost of building the two sizes is almost identical. You might even consider building a 32″ oven.

Forno Bravo sells a lot of 24″ Primavera ovens, but that is a fully assembled and finished oven that can be set on a metal stand, where the smaller oven is quite a bit less expensive (about $400). Plus, the smaller ovens weighs less, and can be more easily moved by two-three people without any mechanical assistance, where the 28″ oven is much heavier. Again, those issues do not apply to cast in place ovens.

Large, 32-36″ ovens are the most popular refractory oven sizes for precast ovens. Forno Bravo’s Casa2G90 (36″) is very popular. It’s interesting to note that Mugnaini doesn’t sell that size, which is odd. The same logic you used analyzing the mid-size oven applies here. The extra cost, effort and space required to build a 36″ oven, compared with a 32″ oven is minimal, so if you have any questions, build a 36″ oven.

The XL 40″ oven is where it gets tricky. It’s clear the 36″ oven does a lot more than a 32″ oven, and the extra overhead of building, firing and maintaining it, compared with the smaller oven are minimal. The 40″ oven is the first time you need to think seriously about the time it takes for fire your oven vs. what you are planning on doing with it. There might be times when you’re waiting 40-50 minutes to fire your oven, putting in another load of wood, and thinking that all you’re doing is making a few pizzas for the family or another couple of friends. And you might be right.

40-44″ ovens are for people with big, extended families, people who throw big parties for lots of friends and neighbors, people who absolutely love to cook, and people who love messing around with their oven. I’ve been there. The Wood Fired Chef (100K+ followers on YouTube) has a 40″ Forno Bravo Premio precast oven kit.

But our kids are grown, and we tend to throw small parties for friends. It’s great when we get the whole family together, but it doesn’t happen that often. And I wondered if I would look back at my personal decision and think that 40″ was just too big.

That’s why I chose 36″.

All the logic about a 40″ oven applies even more, just bigger, to a 44″ home oven. People do it. You can too! But that’s a monster of an oven. You can run a moderate size restaurant or cafe out of a 44″ oven. In general, 48″ is the starting point for a full-size restaurant or pizzeria pizza oven, but you’ll find lots of wood-fired pizzas being made in a 44″ oven. But if you want to throw great parties, hire a professional chef to run your oven for you, and you’re looking forward to cooking everything in your oven. go for it.