Dry-Stack Brick Pizza Oven

[newhopeclan]

Hey all - as my first step into the wood-fired pizza oven world, I decided to try a dry-stack brick oven... something inexpensive and not too permanent that I can experiment with. Never having done this before, I took a shot based on a design I found on line. The design is pretty simple, with a CMU base, firebrick for the hearth, and solid clay brick for the walls and roof. I used a little masonry sand to fill some gaps at the steel angle roof supports. It went together in a day, and would be easy to modify.

I heated up the oven and baked a couple of pizzas. They turned out great, but they took longer than I thought they should. I know this type of oven won't get as hot as a dome-type, but I was wondering if anybody had any tips to make it more efficient. I tried a couple of things, like blocking off part of the opening with brick to keep the heat in while cooking (see Pizza6.jpg). Would it be better if there was a chimney or some kind of venting at the top? Should I reduce the size of the opening at the front? I had a thought to either lower the chamber by a couple of courses of brick, or build a lintel over the opening that would drive the heat lower before it spills out the front. Take a look at the attachments for how it went together, and I look forward to your thoughts.

[scott123]

Re: Dry-Stack Brick Pizza Oven

A chimney draws air into the oven for better combustion, so, yes, you want a chimney.

Your 'solid clay bricks' look a little bit like pavers. If they are, pavers are completely unsuitable for an oven environment. Even if they are traditional kiln fired clay bricks, you're going to find differing opinions on this, but I personally very strongly feel that if you have fire, you should have firebricks.

The gray bricks also look like they might be damp. Damp bricks + intense flame = propensity for explosion = potentially dangerous situation. Safety issues aside, water, if present, is a very powerful heat dampener, as it keeps the temp of the walls/ceiling below boiling temperature until it evaporates- and, in thick walls, can take days (and should take days, for safety reasons). Water in the baking chamber is the kiss of death for wood fired ovens. Work with dry firebrick and dry insulation, and make sure you keep it dry- either by disassembling it between uses, or adding a weatherproofing layer. Should you have no choice and have to begin with wet firebrick, cure it over a period of days.

The thicker the wall, the more thermal mass, the longer the walls will take to pre-heat. Thick walls, once they get hot, will stay hot for quite some time, which is great for retention baking, but, for a 'pizza oven' you generally don't want to have to pre-heat the oven for more than three hours to make pizza. To achieve this, you'll want a wall thickness of no more than 2" (a firebrick on it's side).

Thick walls can provide a form of insulation, but once you go with pre-heat friendly thinner walls, in order to keep the heat in, you'll need to insulate them. Just like combustion will never be ideal without a chimney, an oven won't truly retain heat well without insulation- and this means insulation on all sides- including the floor.

When you bake pizza, you're watching the side next to the fire to determine when it's properly colored so you can turn the pie at the appropriate moment. To do this, you need to the fire on the side. With the fire on the back, you're baking blind. In terms of side dimensions, again, you'll find a few different opinions, but, imo, you want at least a foot for the fire, at least a 6" buffer between the fire and the pizza and at least 14" for the pizza itself- that's a minimum of 32" internal width. For depth, you have a little more wiggle room. If you're okay with one pizza at a time, then, sure, you could probably get away with as little as 14", but if you want two pizzas, you want at least 28"- internally. That's not including the depth of the throat. A chimney should never be in the main oven chamber, as it will allow precious heat to flow out of the oven. The chimney needs to be in the throat.

It's essential to trap heat in the oven with a doorway that's lower than ceiling (about 60% of the dome height is a good number to shoot for) and, for pizza, lower domes foster better top/bottom heat balance by bringing the intense infrared radiation coming off the ceiling closer to the pizza. For a large oven, 15" is a good dome height to shoot for, while a smaller oven like yours would probably benefit from a dome as low as 12".

[newhopeclan]

Re: Dry-Stack Brick Pizza Oven

Scott,
Thanks for all your thoughts. The idea of an exploding brick oven does not excite me, so I want to make sure it is safe. I know firebrick would be best, but this oven is made of about 280 brick, and at $3 a pop, firebrick were a little pricey on a project that was more of a fun experiment for me. You are right, these are pavers, but they are solid fired clay, and I think pretty stable. They were dry when I stacked it up, but probably had a little latent moisture in there that you see being driven out by the fire in the images. I made a removable make-shift roof out of a piece of plywood to keep rain off, but maybe I need to cover with a tarp when not in use so it doesn't saturate in the rain.... I have burned the oven twice and have not seen even a crack yet. Anybody with any experience with weather-protection, I would welcome thoughts.

I don't think I will be disassembling between uses - too labor intensive - and was not planning to insulate, but maybe more of the split (thin) fire brick lining the sides and roof like I did on the back would help.

The comments about dimensions and function are great. The image below shows what I was thinking for lowering the doorway, and has the 60% proportion you describe, so I will give that a try. My ceiling is about 15" tall, but it does feel a bit tall to me, so maybe I will remove one course of brick and drop the ceiling 2 1/4". As for the overall geometry, I think I will stick with what I have for now and suffer through the one-pizza-at-a-time issue, but in the future may try something different. This is why I liked the dry stack option.... easy to modify.

[wotavidone]

Re: Dry-Stack Brick Pizza Oven

I don't agree that fired clay pavers are completely unsuitable for an oven, unless "fired clay paver" means something completely different in the US than it does here in Oz.

They might not be as good as fire brick, but fired clay pavers are quite commonly used for wood fired ovens in Australia.

Almost all firebricks are imported, and are quite expensive.
Fired clay pavers seem to be stronger than solid red commons, the other low tech substitute for people who can't get or can't afford firebrick.
They are certainly harder to cut than a solid red.
I've been using my clay paver based pompeii oven for 2 years now, I've had it hot enough that my infrared thermometer goes over range (it reads to 1022 F).
No spalling, and the oven is a mixture of pressed pavers on the floor and lower walls and wire cuts for the upper portion of the dome.

It is vital to keep the water out. A wet brick really could explode if heated quickly enough.

[Lburou]

Re: Dry-Stack Brick Pizza Oven

Interesting oven you have.....If you would consider another tack, look at this cast oven or this one. There are many other cast ovens on fornobravo, just search for them (a cast oven will fit on your base). Seems like a member named 'Sonomacast" had some good threads on cast ovens. HTH

[scott123]

Re: Dry-Stack Brick Pizza Oven

Mike/Wotavidone, when I talk about 'pavers,' it's concrete pavers. For me, personally, anything kiln fired is a brick, not a paver.

Mike, as long as you're 100% certain that these are kiln fired, then you're a bit better off (some people are okay with traditional bricks for ovens, others, like myself, aren't). From the photo, though, those look a lot like concrete pavers. Concrete, if exposed to intense heat, will break down pretty quickly.

Regarding the geometry, bear in mind, it's more than suffering through the one-pizza-at-a-time issue, it's also the baking blind aspect that I spoke about earlier. You really need to see the side of the pizza closest to the fire as it bakes to know when to turn it. If you're going to have an unevenly shaped oven, it's far better to go wide than deep, so you can put the fire on the side rather than the back.