Wood-Fired Oven - and how to build one in your backyard

“Heat equals flavour.”

Turning up the flame a few notches on my stovetop, I’ll mutter this cooking quip under my breath from time to time in the kitchen. A self-fulfilling prophesy. And it's hard to dismiss the truth behind this culinary aphorism when cooking with the new wood-fired oven in dad's backyard.  There's just something about a pizza cooked for sixty seconds in fiery heat that elevates the flavours to heights unimaginable in a standard electric oven. 

This is a story about building a wood-fired oven in a St. John's backyard with my father. If you want to build one yourself, hopefully this post will inspire you to get started. And if you’re just curious about what it takes to construct a wood-fired oven, you'll find plenty of information here to whet your appetite. And regardless of whether you build one or not, hopefully you'll come away with at least one message: heat equals flavour.

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Classic margherita pizza on sourdough crust

Inspiration in Australia

The first time I considered building a wood-fired oven was during a rock climbing trip in Australia. It was June of 2015 and I had hitched a ride with the Victoria Climbing Club to the town of Natimuk, a quiet farming town besieged by climbers located some three-and-a-half hours north of Melbourne. Out of the plains rises Arapiles, the famous rock formation beloved by climbers for its traditional climbing ethic. In the climbers' campground, lovingly nicknamed “The Pines,” I met my new climbing friends.

Naturally my climbing partner for the day ended up being a retired chef. In the critical moments it takes to partner up with a new climber, we had clicked. Never mind that his shoes were from the 90s and that he had said something about his harness being a prototype from the 80s. By the time we roped up for the first climb of the day I was glad to call him my friend. He was a chef-turned-forest-firefighter who built wood-fired ovens in the off season. “So you cook a lot of pizzas?” I asked. “I cook everything. Last week I roasted a whole chicken.” I was enamoured. I can’t even remember what we climbed that day. Later he pointed out a community wood fired oven in the town of Natimuk, built by the city, which was available for public use. “I’ll build maybe twenty in one year. Backyards all over Melbourne and Geelong have ‘em now. It’s more of a hobby for me, you know. It’s dead easy to build one. Anyone can do it.”
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Arapiles, near Natimuk, Australia, where I met a climber who told me about backyard ovens.

Dad emerges like some masonry hobbit from his root cellar with some potatoes after an early winter snowfall.

I emailed dad about it. He had just finished his root cellar and he was eager to dig into another project. He had become a sort of fringe masonry zealot of the homesteading domain. Before long I was getting images in my inbox of ovens carefully drawn on engineering drafting paper. This is promising, I thought.

The timeline went something like this: a winter of planning, drawing, procuring. Dad began assembly in the basement, cut lots of bricks. More emails. I quit my job in Texas, drove North to the border. A foundation built, then the oven. Dad and me working on construction throughout the summer. Autumn came and went and the oven was done just before the first snow. We couldn’t cook with it just yet, though. Our patience had to be tested with a “tempering” process. That is, slowly heating it at successively higher temperatures to reduce risk of thermal shock and cracking. Finally, after a long winter our wait was over. In the spring of 2017, two years after that chance encounter with the Australian rock climber, our very own wood-fired oven was ready in our backyard.

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How to build a wood-fired oven in your backyard

There are websites dedicated to wood-fired oven construction, so I’ll spare you mind-numbing details here. I can personally vouch for this four-part YouTube series, for instance, since it's what dad and I referenced constantly when building ours. Despite omitting the details, the instructions below will provide a good overview of the project from beginning to end, specifically tailored to building one in a St. John’s backyard.

Moose sausage and mozza pizza with reduced spruce tip sauce on sourdough crust

​Step 1: Plan

Take a moment to think about how much work it is to build an oven and how much it costs. Still want to do it? Good! 

First of all, the lingo: it’s called a Pompeii-Style Wood-Fired Oven. Size will dictate the whole project. Ours is 30", measured by inner diameter. This is on the small end but still plenty big for pizzas, breads, and roasts. The size of dome will dictate size of door, since there’s an important proportion you want to get right. This dome-to-door ratio will ensure that your fire gets enough oxygen to burn and that your chimney draws smoke effectively. For instance in our case the door opening is 16” wide and 10” high, corresponding to the recommended (door width):(dome inner diameter) ratio of  16:30 and the recommended (door height):(dome height) ratio of 10:16.

Proud backyard pizzaiolo

Plan where you want to put your oven. Once it’s built it's pretty much permanent. Estimate the total time and money investments. Our took several months to build (albeit part-time and in no rush) and cost about $3,000 in materials.
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Step 2: Procure and pre-assemble

Top-down drawing of the oven drafted by dad using PowerPoint. Typical engineer! Careful planning paid off when it came time to lay bricks.

Once you've got a pile of fire bricks, you'll need a hand-held angle grinder to cut them to size. You'll also want to grind off corners on the inward facing sides, taking more off the edges for the higher tiers toward the top. Mark on them with a pencil and stack up a little pretend oven as you go. Cutting is done with a masonry cutting blade and grinding is done with a masonry grinding wheel.

Build your wooden formwork now, too. Get a hold of some wooden board and some power tools. The formwork is a wooden support structure that holds the bricks up before they get mortared together permanently. It will help you pre-assemble the oven and it’ll be crucial when you go to actually build it.

Tip: fire bricks are very different from red bricks you’re probably used to. They are solid (they have no holes) and they are bigger than red bricks. They have a high alumina content making them fire resistant so that they won’t crack under intense heat. They also vary in quality per batch, so it’s worth getting all your bricks in one go for consistency. When grinding the bricks, go to the countryside if you can. It makes a racket and will piss off your neighbours in the city.

Tip: we built the form using four 15” radius wooden boards all intersected in the middle to make equivalent angles of 30 degrees. They sat on a 30” diameter circular board propped up 1” from the ground. Everything was glued together. A bandsaw proved a valuable asset for cutting precise circles.

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Step 3: Build the oven footprint

This is just a poured concrete foundation. Clear the ground a good ways to get roots out, and dump a bunch of crushed stone and sand on top. Pour your concrete and reinforce it with rebar to avoid cracking.

Tip: use Quikrete concrete, a standard premixed aggregate containing Portland cement, sand, and stone.

Clear the ground at your chosen location and pour in some crushed stone.

Pour your concrete and reinforce it with rebar.

Completed reinforced footprint for the wood fired oven.

Step 4: Build a foundation and the oven floor

Use cinder blocks and stick ‘em together with mortar. When you've reached your desired height, cover the span with a cement board. This serves as a structural support, on top of which you can pour concrete. We used Durock fibreglass reinforced cement board for this and topped it with a layer of Quikrete. We let it set, then slapped on another layer - this time of Portland cement mixed with heat-insulating aggregate. We used vermiculite for this, a lightweight aggregate with excellent insulating properties. The floor of the oven will get very hot, and we don’t want this precious heat escaping into the foundation. This insulating layer of the floor minimizes this unwanted heat egress. 

Tip: cinder blocks come in standard sizes, so they may dictate the size of your platform.
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Stack cinder blocks to construct your foundation.

Use mortar to hold cinder blocks together.

Completed foundation walls. Now we need to cover the span!

Lay your chosen fire bricks down to create the floor of the oven. Later we'll surround this with heat-resistant cement. The formwork (you built this in Step 2) will get placed lovingly on top of the floor as you prepare to construct the dome.

Tip: say goodbye to your formwork! You’re going to cover it with bricks as you build you dome, then set fire to it when the oven is complete.
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Durock fibreglass reinforced concrete board covers the span.

Heat resistance concrete is poured on top of the Durock cement board.

The oven floor, consisting of just fire bricks, is added. The formwork for the dome will be placed on top (not shown).

Step 5: Build the dome

Stack concentric circles of fire bricks, using your wooden formwork to guide you. When adding layers, stick them together with refractory mortar. Yes, refractory mortar. It’s heat resistant and won’t crumble under high heat. This is important!

Tip: we couldn’t find real refractory mortar in Newfoundland. So instead we used Vesuvius refractory concrete mix to hold the bricks together. It’s not as easy to use as a mortar, but it worked out fine in the end. The stuff is expensive, though, coming in at about $100 per bag (we used around 5 bags in total).

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The formwork is clearly visible in this image. It's essential in getting the job done right.

Fire bricks are laid in concentric circles and pasted together for heat resistant mortar.

The whole works is given a coat of heat resistant concrete.

Step 6: Build the entrance

This requires some attention because the intersection of a dome with planar surfaces means you get some awkward geometry. Build a formwork for the entrance, too. Once you're done, remove the door and keep it for later. Then set fire to the wooden formwork inside the dome. 

Tip: Prop the entranceway formwork with shims. This way you can take it out easily when you’re done construction - and better yet, use it as a door!

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Step 7: Insulate the dome

First put a layer of refractory mortar on the dome just to smooth it out and close up any holes. Then cover this with a layer of insulation and prop it down with chicken wire. Top this off with a final couple layers of ordinary mortar. Now it’s really looking like a proper oven!

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The dome is covered in insulation and then held together with chicken wire. You can see the soot from burning the inner formwork.

The insulation is coated with concrete.

Finally, it's given another layer of concrete. It's looking like a real oven!

Step 8: Add a chimney (optional)

We used an insulated 4ft house chimney, but the choice is really yours what you use and if you even want to use one. We thought this chimney was perfect because it vented smoke high into the air. Consider this if you want to keep neighbours happy on a windy day when they are hanging laundry on the line.

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Step 9: Build little house for your oven (optional)

This is just to stop water ingress and mitigate freezing and cracking in Newfoundland’s temperate winter. It worked well for us! Our oven survived winter crack free.

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Here's our finished oven, complete with 4-ft chimney and covering house. We had to wait till spring to use it.

Step 10: Temper the oven

Start with a 10 minute burn. Let it cool. Now add 10 minutes to your subsequent burns until you reach one hour. When you've reached an hour, it’s ready for operating at full blast. Enjoy!

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Sourdough wheat-rye getting a healthy crust in the hearth. Bread requires a lower oven temperature so I'll often pop one in after making pizzas.

Written by Erik Veitch in July 2017
Edited by Michael Lee. Thanks, Mike!

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