My WFO Build

Some of my followers on Facebook know that I’ve been building a wood-fired oven this year. I’ve got build threads documented on FornoBravo.com and PizzaMaking.com both of which have been very helpful, but I want to get caught up here due to so many Berserkers who’ve expressed and interest.

The basic design comes from Forno Bravo’s Pompeii Oven design, which is more of a set of design guidelines than it is a specification. It’s great of them to make this information public, as well as hosting a forum for amateur oven builders, given they are in the oven building business themselves. Every builder at Forno Bravo puts their own unique fingerprint on the design, and the sum of their knowledge is captured on the forum.

The overwhelming design philosophy at Forno Bravo’s forums favors a Tuscan-style oven (high dome/hemispherical profile) where serious pizza people favor a Neopolitan-style (low dome/elliptical or three-centered arch profile). The Forno Bravo docs brush off this as a non-issue, but the truth is their users are as interested in roasting turkey as they are in pizza, and they typically start their pizza learning process after their ovens are done. I’m more concentrated on pizza and bread, so I applied the Pompeii design guidelines to what I could learn about Neopolitan oven building, specifically with the help of the people at PizzaMaking.com:
http://www.pizzamaking.com/forum/index.php?board=51.0

The Neopolitan style of design I think is a lot simpler and easier to put together, but it does have a wrinkle that the low-dome puts outward pressure on the walls, and it needs some sort of external buttressing to keep the structure from collapsing. A hemispherical dome is self-supporting, but I’m convinced much more time consuming to build. I hired out to a metal fabricator for my external buttressing as you’ll see. Everything else was done myself.

The design I settled on is for a 36" round oven with a 14.5" elliptical dome, buttressed by metal straps. Somewhat counter-intuitively, the vent is outside the dome, which allows for a specific air circulation inside the oven, and much more efficiency for holding heat. We’re planning on it being the cornerstone for an outdoor kitchen, but who knows how long that will take to finish. The oven is functional now, with only cosmetic work remaining. I plan to tile the outside of the dome, but I had to special order frost-resistant tiles and they have a long lead time.

I poured the foundation over my Christmas break. 6" thick reinforced concrete:

The stand is made from dry-stacked cement blocks, with every other core filled with rebar and cement. Halfway through, a wicked storm claimed my canopy, but I brushed it off and moved on:

The hearth slab is 4" thick cement with cement backer board underneath, heavily reinforced with ½" rebar. There’s a temporary wooden support to support the slab while it cures, which isn’t pictured:

The bricks are HC Muddox firebricks. The floor is laid out in a herringbone pattern to prevent the pizza peel from catching on an edge. Bricks were cut using a wet saw and an angle grinder:

The center pipe is cut to give me the 14.5" dome height, and I cut a rotating template for the elliptical dome profile:

Next step is a vapor barrier, then 4" of ceramic fiber insulating board. This is a rigid high-temperature board made for insulating kilns. I purchased this from the Forno Bravo store:

Next, the walls go up. The mortar is Heat Stop 50, a refractory mortar designed for high heat:

Next I installed my metal buttress and prepared to fill the oven with sand to form the dome:

I filled the oven with “found items” to save a little on sand, then formed the dome with damp sand, and covered it with newspaper to keep sand out of the brickwork:

Built a brick cutting jig so I could taper and bevel the bricks to fit them more tightly into the dome shape, then up and away. This took me 2 days:

Next, pull out the sand, and hope it stays up There wasn’t much doubt actually - as I pounded the keystone into each chain, I could feel the dome tighten up. The final plug was really tight to drive in.

We then had some rainy weekend where I finished building my last metal fab project - the insulated door. It’s 4" thick and filled with the same ceramic fiber insulating board. With this door in place, I can cook from residual heat for days after firing the oven. Typically it’s Day 0 (pizza) = 900ºF+, Day 1 = 500ºF, Day 2 = 350ºF, and then it drops about 50ºF/day.

Next, the outer arch and vent. These are Ebony firebricks from HC Muddox and more Heat Stop 50 with charcoal color added. The vent plate is from Duravent, to support a 6" dual-wall chimney:

With that, it was time to start curing fires. The regiment is to start all-day fires at 300ºF, then rising 50º/day until you’re at pizza temps. The goal is to slowly, gently drive moisture out of the masonry without flashing it to steam which will cause cracking and spalling. When the dome starts getting into the pizza range, the soot burns off the walls, as shown in the last pic. When the dome is completely cleared, that’s when you know it’s time to cook:

I remember following this on FB. Seemed like it took an eternity. So many steps. Well done Larry!

Next isn’t so glamorous. Ceramic fiber insulating blanket, another refractory insulator purchased from Forno Bravo, blankets the outside of the dome, then finished the dome shape with an insulating concrete made from perlite and portland cement:

Thanks Brian. Yes when I look at the entire project it’s a little mind-boggling the scope of it and the level of detail. About 2 years of research went into it, and even that was really simplified by the Forno Bravo docs.

Here’s a video showing the draw on the chimney, which is pretty good. A little smoke always escapes and stains the front on these ovens, especially before the chimney is heated up, but that’s why I went with the ebony bricks.

Last post brings us up to date. I rendered the dome with “Quickwall Surface Bonding Cement” which is a fiberglass reinforced stucco, to which I added an acrylic admix to make it waterproof. I still need to render the walls on the stand, then plan to finish the dome with a tile mosaic and the stand with fieldstone. This is how it sits right now, basically functional but waiting for a few finishing touches:

Rad. Thank you for sharing. This is on the list for next year.

Do the experts ever mention using a catenary shape for the dome? That is the shape of traditional igloo roofs and is very efficient from a structural standpoint.