Building a WFO (wood Fired Oven)

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In the spirit of off the gridness and in an effort to be more self-sufficient, my wife and I recently tackled a new project at home.  We built a wood-fired oven, or WFO, if you prefer. 

An outdoor wood-fired oven gives us another option for many kinds of cooking.  It also provides a great accompaniment to the barbecue.  The WFO is a lot of fun to built and use.  It provides a lot of feel good factor for having done it ourselves with little money.  Of course, it also makes great tasting food.

We over-researched the subject by reading several books and by searching online before finally building it.  We need not have prepped so much.  Two of the most helpful resources were http://www.traditionaloven.com and the book “Build Your Own Earth Oven, 3rd Edition: A Low-Cost Wood-Fired Mud Oven; Simple Sourdough Bread; Perfect Loaves” by Kiko Denzer.


Materials list and cost:

I used:

less than 1.5 yards of 5/8 minus for the entire project – about $40.

"Urbanite" and large rocks - free.

Concrete block – free from freecycle.

Sand – free from river.

Coarse Sawdust – free from a local lumber mill.

Perlite – about $30 from the hardware store.

Clay – $150.  (It could have been free with more elbow grease)

Material for the door – free from around the property.

 

Total cost:        under $200.


Step 1: Pick Your Type of WFO

Type:  We discovered that there are several types of WFO’s.  Which is best depends on who is writing the article.  Our primary concerns were the difficulty of the project, the cost of the project, and the look of the project.  A $15,000 brick and marble WFO would look silly sitting next to our farmhouse, would be way beyond our budget, and might be beyond our construction ability.  We decided on an adobe, cob, or clay oven.  They exact material seems to be interchangeable.  Since we are part-time potters, we happened to have a sixty-gallon garbage can full of left over clay from the past couple of years.  We decided to use what we had

Step 2: Location, Location

Location:   One of the most important and also most difficult parts of this project was picking a location.  The WFO requires a location that places its back to the wind.  Ideally, it should be out of the elements.  It also needs to be accessible enough to be useable.  We finally decided to locate our WFO off the end of our screened front porch, facing away from the wind.  This would require rebuilding that end of the porch to allow for a screen door, building a shed roof for protection from our very frequent rain, and leveling the ground in that area.

Step 3: Size Matters:


Size:   We wanted something big enough to bake a small pizza, a small roast, or turkey, or a couple of loaves of bread at the same time.  We wanted it a bit on the small side so that it would use less firewood and so that it would blend in.  We settled on an inside diameter of 22 inches wide by 16 inches high.

Step 4: Getting to Work: the Foundation

The Foundation:  I started the project by locating the oven far enough away from the porch for safety yet close enough for convenience.  I dug a square hole 54” wide and about 6” below the frost line and leveled the hole.  Into this square hole I packed level about 4” of 5/8” minus gravel. 

Step 5: Building Up the Base:


Upon this foundation I laid a square of the 8”x8”x16” concrete building blocks, three blocks to a side.

Step 6: Completing the Foundation:


I stagger stacked five more layers of building block.  After each layer of block, I filled the square with “urbanite” and large rock, filled all of the spaces and covered the rubble with 5/8” minus, and compacted it all with a length of 4”x4”.  I did not fill the last layer of block so that the insulation layer would be deep enough.  I capped the last layer of cmu with the 4”X8”x16” concrete cap. 

Step 7: Adding the Insulation Layer:


The resulting 12” void was filled in with an insulation mixture made of sawdust, perlite, and clay slip.  Equal quantities of sawdust and perlite were carefully measured by the shovel-full into a wheelbarrow.  Clay slip, clay mixed with water into a sour cream consistency, was added until all of the particles were coated with clay.  A rough ball made of the insulation mix did not splatter or break apart when dropped from waist height.  This insulation layer was packed and leveled.

Step 8: Fire Brick Layer - the Oven Floor:

The Oven Floor:  We purchased 16 medium-density firebricks from the fireplace shop and set them into the insulation layer.  More of the insulation material was used to level the floor of the oven prior to building the oven itself. 

Step 9: Building the Oven:


The Oven:  I used a string with a pencil to draw a 23” diameter circle on the firebricks.  Sand from the nearby river was screened and used to make a sand dome.  We dumped wet sand in a pile on the bricks and painstakingly molded a dome.  It was not as easy as it should have been.  This was the most frustrating part of the project!  Finally, after starting over a few times, we achieved a nice-ish, 16” high, rounded dome.  Several layers of wet newspaper were plastered over the sand so that the clay layer would not stick to the sand.

(sorry, no pics of this annoying step)

Step 10: Building the Oven - the 1st Layer:


Our soil is very heavy with thick red clay.  Either it is too wet to work, or is so hard that you need a pick to get it out.  We had originally thought to dig our own clay, mix it with sand and straw, and to use this material for the oven.  However, we decided to cheat a bit bought some very rough clay intended for large structural structures from the pottery supply warehouse.

We packed this clay 4” deep around the sand dome.  Layer by layer we pressed the clay into itself around and over the dome, being careful not to press into the sand dome. 

My wife then used a 2”x4” to not-too-gently smack the clay dome into a proper shape.  The smacking helps consolidate the clay into one cohesive shell.  Just do not smack it too hard or you will end up with a bulge on the opposite side or around the base.  An arched door was drawn onto the front of the inner clay shell.  It was about 66%, or 10.5”, high by 12” wide.

Step 11: Building the Oven - the Insulation Layer:


Over the inner clay dome, we laid up a 4” layer of the same insulation material used for the floor.  The insulation layer stopped about 4” short of where the doorway was going to be cut. 



Being impatient, we cut doorway into the dome.  The doorway was cut with a bevel to keep the door from falling in.

Step 12:

The 3rd and final layer of the oven was a 2” layer of clay.  This exterior shell was layer up in the same fashion as the other two layers with great care not to push the clay into the insulation layer.

The exterior clay shell was wrapped over the exposed insulation layer around the door.  This created a continuous clay shell with a 2” reveal around the doorway.

After some drying time the oven was now firm enough to remove the sand.  Using a garden trowel my wife carefully dug out the sand.  When she hit newspaper, she knew that she had reached the inside of the dome.  After the sand was removed, the newspaper was carefully peeled off the inner clay dome.  A smooth piece of rounded wood used for shaping bowls on the potter’s wheel was used to smooth out the rough spots on the inner dome.

Step 13: Finishing the Oven:


The exterior shell was paddled and shaped into a smooth cover.  The final layer had to dry a bit before it could be smoothed completely.

My wife threw an onion shaped finial for decoration on the top of the oven.  She then carved various designs into the dome.

A door made from 2x6’s was cut to shape.  1x6’s were cut to go over the face of the door and to extend 1” beyond the door in order to act as a flange to keep the door from falling in.  An extra chunk of tile-backer was cut to shape and screwed onto the inside surface of the door for a heat shield.  A pair of handles left over from a previous project completed the door.

Step 14:

Getting it to work:  A small fire was lit inside the oven to slowly dry it out from within.  The sun worked to dry it from without. 

Step 15: Time for Dinner!


After it was dry (enough), we brought it up to white hot, pulled the coals out, put the door in place, and soaked it for about 15 minutes.  While it was very hot, we cooked up a few small pizzas.  It actually worked!

Since then we have baked bread, pizzas, backed beans, veggies, and bagels in it.  We have learned when to pull the coals so that the food does not taste too smokey.  The oven is a big hit.  Many of those who have seen it want to build their own.

The WFO’s potential and use are obvious.  We have never used “firewood” in this oven.  We have always used sticks, branches, and other left over non-treated wood products for firing the WFO.  Usually about ½ of a five-gallon bucket is all that is needed per firing.

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    55 Discussions

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    jon ballIamTheMomo

    Reply 3 years ago

    You wouldn't think so,looking at it now. The exterior doodads have all popped off. The clay is pitted from the pounding wind driven rain. The flange around the mouth keeps cracking apart and falling off. But, with about ten minutes off clay patching, it still makes great pizza and bread, baked beans, etc. It will come down this summer, probably. Maybe not. Gotta build a new chicken coop, get the duck pen up, repair some of the raised beds,............

    we used a mix of lowfire 04 up to highfire cone 10. we've had many problems with it. The decorative items have all separated. Large cracks (1/2") have popped up here and there. The mouth has lost most of its structure. However, we just keep slapping clay on it to fill in the cracks and keep on going. Cooked last weekend with it. Got it to 1600F inside, still cool outside, flash cooked the first pizzas, kept cooking the rest of the day. It was still warm the next morning. We had intended to rebuild it this summer, but the misses has been diagnosed with wheat, egg, and diary allergies. so................not sure at this point. I am trying to win the arguement for conversion to a forge - I've a hankering to pound out some sharp n pointy things.

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    saosport

    4 years ago on Introduction

    Does anyone know how one of these would hold up in the Midwest? I live in WI and thought it would be great but I am not sure how it would hold up in winter.

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    jon ballilhadad

    Reply 4 years ago on Introduction

    Sorry about the delay. Yup, just mix clay with water. Runny or thick, it is up to you.

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    Duplo for Daddies

    6 years ago on Step 15

    This looks great! I am working on starting a bakery, and have been wondering about doing something like this for some more special breads, in addition to stuff baked in a regular oven. Wood in my area is kind of sparse, so I might take on your challenge of making a gas powered version.
    I am wondering (you might have an answer), are these kinds of ovens more energy efficient than modern kitchen ovens or industrial ovens?
    I'll let you know if I ever get to making my own one.

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    drewgrey

    7 years ago on Introduction

    Good job, Did you say half a 5 gallon bucket of wood to bring it to temp. Thats amazing. Mine takes alot more than that. I have a laser thermometer that says that I have an average cooking temp of 750 or so. Do you have a metal peel yet?

    2 replies
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    jon balldrewgrey

    Reply 7 years ago on Introduction

    Ya sure. We bought one from our local Grocery Outlet. It was a tad bit wide so I had to shave it up a bit.

    Tell me about your laser thermometer. I've not seen one of those. We would like to be able to tell just how hot the oven gets. "white" "red" "orange" works pretty well when temping metal, but not so much for the inside of a dark oven.

    Remember that for our heat we burn the wood to coals and then soak the oven with the door on for a couple of hours. That really saturates the base and the oven with heat which is then reflected back into the cooking chamber. Patience is a virtue here. If we have a long day ahead of us we will renew the coals and keep a few pushed to the back of the oven. It does take more wood then. Usually we use scrap fir or cedar to start it going and the heating fire is from maple or alder. We are curious how this would work with charcoal briquettes right out of the bag. I suppose that this could be rigged to use gas as well. Curious.

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    drewgreyjon ball

    Reply 7 years ago on Introduction

    We got our laser thermometer from sears but harbor frieght has them cheap also.It gives a reading off whatever its pointed at. We got it for brewing beer but have found it entertaining for other stuff ( like testing my cladding compound for heat retention and insulation).
    We start our fire at least 2 hours before showtime and continue burning while we cook. Since we have an interior diameter of 36" there is room for the fire at the back and pizza in front. After every few pizzas we pull the fire to the front to clean the cooking area, or after a cheese and topping malfunction. A great benifit of having a fire while cooking is that the pizza wants to be cooked from both sides at the same time. Perfect crust and slightly tan cheese!

    IMG_9796.jpgIMG_1871.JPG

    Lovely work.
    I have lots of questions.
    Can you please add a photo of your door?
    Is there a chimney, or does all the smoke come out the front?
    Where does the fresh air come from to feed the fire?
    What method do you use to remove fire and ash before cooking?
    Thanks.

    1 reply

    No chimney. All smoke come out of the front. The wood is burned with the door off. When only coals are left, the door is placed. After a period of time (the "soak" period) the door is removed. we bent a piece of metal, attached it to a stick, and use it to scrape out the coals into a steel bucket. A rag wrapped end of another stick is soaked in water and used to "mop" out all (most) of the charcoal.

    I am getting ready to post another series of pics. we've torn off the exterior layer, mixed in about 40% more sand, have placed the new exterior layer back on, are letting it cure to the right consistency for wacking (preshaping) then final shaping. We are going to add on an arched entry made of clay which has been fired in the kiln. This will give us a place and the support for a front located chimney.

    I'll post pics of the hardware then as well.

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    tim_n

    7 years ago on Introduction

    You wanted pics, I post pics :)

    Mine is more rustic, I've not added the final finishing clay level. The odd rustic look is made by the insulation - that's clay slip mixed with sawdust. Seemed to do the trick anyway - only started getting really hot after we'd been using it about 4hrs. First pic as the pizza was in, 2nd pic as I removed the first ever cooked pizza.

    pizzaoven.JPGpizzas.JPG
    1 reply
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    tim_ntim_n

    Reply 7 years ago on Introduction

    If you want to see my pics you can goto www.waark.com and see the steps I used.

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    brazell

    7 years ago on Introduction

    Great job!!!! It looks beautiful! Can you take a pic of the door?