Inspiration in Australia
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.
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.
Step 1: Plan
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.
Step 2: Procure and pre-assemble
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.
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.
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.
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.
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).
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!
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!
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!
Written by Erik Veitch in July 2017
Edited by Michael Lee. Thanks, Mike!
I'm Erik, the Burnt Chef. I'm a Finnish-born Newfoundlander living in Norway. I have a passion for cooking and a deep fascination for the culinary history of the North. Simplicity guides my cooking. Time, place, and history guide my storytelling. This is my personal blog about food.