bringing durable strawbale structures to wet climates for over 15 years
volume 4, issue 5
November 2015

designing natural buildings &
teaching hands-on workshops

Build a Clay Pizza Oven
in Your Yard!

by Sigi Koko

How to build a wood-fired pizza/bread oven using local natural materials

 If you are looking for a small project to get your hands (and feet!) dirty testing out some natural building skills, then building a wood-fired oven is a great place to start.  If you have a little help, it takes just a couple days to build, then a few weeks to let it dry out (during which time, you can sculpt your oven to any shape), and then you're ready for a pizza party!!

What is a cob wood-fired pizza oven??'s a baking oven that is heated by lighting a fire inside, the fire warms up a thick clay oven wall, and the clay wall remains warm for hours after the fire is pulled out.  So you build the fire in the same oven area that becomes your baking space.  The beauty of this type of oven is a) the oven is simple to build using local, natural materials and b) the oven temperature remains very even throughout, with no hot or cold spots.  Plus, it's a fun project to do with a bunch of people and you can celebrate your accomplishment with a pizza party!

Decide what size oven you want to build.

The appropriate size for you will depend on how you intend to use your oven.  Here are the variables effected by size:

  1. The larger the oven, the more materials you need to build it.  For example, an oven that is 36" wide inside takes about twice as much clay, sand, & straw as an oven that is 24" wide inside.  And more materials translates to more building time as well.
  2. The larger the oven, the longer it takes to heat up.  For example, a 24" wide oven takes about 2 hours of fire to heat up, whereas a 36" oven takes about 3 hours.
  3. The larger the oven, the more mass, soooooo, the longer the oven stays warm.  This means you can cook in it longer each time you fire it up.  Especially if you a good insulation layer on your oven.
  4. And obviously, the larger your oven, the more pizzas you can bake at once!  (Or whatever you are cooking...)

So, think about how long you want to wait for your oven to heat up, how long you want the oven to stay hot (larger oven for pizza party use, smaller oven for personal use), and think about how big of a project you want to take on (do you want to build a small oven over 2 days or go for a larger oven and spend longer to build)??

Typical sizes are 22-1/2", 27", or 36" (these sizes work out well with the size of standard fire brick).  Of course, there are mini ovens as well as massive ovens, but those are mostly for special use applications.

Decide if you will build a roof over your oven.

A roof will help protect your oven from the elements, and allows you to bake even when the weather is sucky.  Rain, especially, will erode a clay oven over time.  You can either allow that, replaster your oven every year, put a tarp over your oven when it's not in use, a roof to protect it.  If you decide to build a roof, those materials will be in addition to those listed below.  Build your roof so you have plenty of room to stand underneath, and to clear any smoke out.  I recommend at least 7 feet of clearance under the roof.

Gather your materials.

You will need the following materials to build your oven:

  1. Clay:  Clay is your essential ingredient, because it is the binder that holds all the materials together.  When wet, clay is sticky.  When it dries, it is strong & hard.  You can use clay-soil OR you can purchase dry, bagged, pottery clay.  (see video below on how to test your soil for clay content.)  If you are using clay soil, you will need to determine the proportion of clay in your soil (it may feel like it's 100% clay, but it rarely actually is...usually there is sand in there as well).
    HOW MUCH?  The amount of clay needed depends on the size oven you are building.  Here I am talking about total clay, so if you are using soil with clay in it, you will calculate the amount of clay based on the percentage of clay in the soil  (So, if your soil is 50% clay & 50% sand, then every bucket of soil = 1/2 bucket of clay & 1/2 bucket of sand.)  So total clay needed is about 25 gallons for a 22-1/2" oven, about 35 gallons for a 27" oven, and about 50 gallons for a 36" oven.
  2. Sand:  Sand is your aggregate.  It reduces shrinkage of the clay as it dries and it adds total strength to your oven walls.  You need to use angular sand, not smooth sand or silt.  Concrete sand is pretty cheap & works great.  I also use sand to build the form for the oven (this sand is taken out at the end and can be used to make plaster if you finish your oven that way).
    HOW MUCH?  Plan on about 300 to 500 lbs of sand if you are using clay soil with at least 50% sand content; if you are using bagged pottery clay, double the sand.
  3. Straw:  Straw is used to create an insulating layer for your oven.  It is also helpful to stand on the bales as your oven gets tall.  Make sure your straw is clean, dry, and mold-free.
    HOW MUCH?  You need about 2 to 3 strawbales for a small oven and 3 to 4 strawbales for a larger oven.  If you plan to sculpt your oven into a fun shape, make sure you have ample straw.
  4. Firebrick:  This is what I like to use for the floor of the oven, because they don't split in the heat of the fire and they have extremely squared edges, so they make a really smooth floor.  Typical firebrick are 4-1/2" x 9" x 1-1/2".  You can lay out the bricks for your desired oven size to see exactly how many you need, but below is what I use as a reference.
    HOW MUCH?  I use 15 firebrick for a 22-1/2" oven (12 for the floor + 3 for the door opening), 22 firebrick for a 27" oven (18 for the floor + 4 for the door opening), and 37 firebrick for a 36" oven (32 for the floor + 5 for the door opening).
Plus, you will need a water source, some newspaper strips, and whatever you want to build your base out of (stone, brick, etc.)

Note: I highly recommend collecting extra material than you think you need so you don't run out of anything mid-stream.


Have fun building & happy baking to you!!!!

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In This Issue...

Feature Article
"Build a Clay Pizza Oven in Your Yard"
What's Happening
upcoming events
Low Hanging Fruit
simple eco-living tips
Recommended Reads
natural building books
About Sigi
my approach to design 

What's Happening

What we're up to at Down to Earth Design...

Just updated the GLOSSARY on my blog

with short descriptions of various natural building materials and tips on where best to use each

Check it out HERE
and post a comment if you have questions or suggestions

Low Hanging Fruit

small habits that make a big difference...

Avoid bottled water


Ok, so maybe this is obvious, but there are some really motivating variables I'd like to share to help really shift this habit for good...

What's the big deal?

1.  First some common sense...tapwater costs 1/10,000th of the price of bottled water

2. Public tapwater is MUCH cleaner & more highly tested than bottled in point, 22% of bottled water tests above allowable health limits for chemical contaminants including e.coli.  And bottled water that does not meet water quality standards for drinking water is allowed to be sold to the public.

3. The plastic used to produce the bottled water uses 17 million barrels of oil per year (equivalent to gas for 1,000,000 cars per year) AND it takes 3x the amount of water to produce the bottle as is does to fill it.  Add to that, that the production of a PET bottle results in 100x the toxic emissions (including dioxins) as the same bottle made out of glass.

4. Prolonged contact between the water and the bottle OR if the bottled water is heated... sitting in your car, outside on a sunny day, etc... cause chemicals from the plastic to leach into the water.  So if eating a plastic bottle doesn't sound appealing, drinking bottled water from plastic should be equally unappealing.

5. Only about 20% of plastic water bottles are recycled, which means most end up in landfill or as litter.

The Solution:

Drink your water from glass, ceramic, or stainless steel containers filled with tap water.

Will save you money and improve your health.  Win-win!

For more info:

And remember, once you shift a habit, it's yours for good!

Recommended Reads

THE RESOURCE for building a cob oven:

Build Your Own Earth Oven by Kiko Denzer

Seriously, get this book before you begin to build your cob oven.  It has everything you need to know to build a perfect oven.

click the cover above for more info or to purchase

My approach to design...
Sigi Koko is the principal designer at Down to Earth Design, which she founded in 1998 to help her clients manifest their dreams of living in a natural, healthy home.  She translates each client’s vision into a unique building design that reflects their personality and lifestyle, while responding to the surrounding landscape and climate.  Sigi’s uniquely collaborative design process provides a high level of information and support that encourages her clients to engage fully throughout design and construction.  Sigi also teaches natural building workshops that empower her clients to contribute creatively during the construction of their own home.

All of Sigi's projects are designed to function in synchronicity with their environment.  Each building relates to seasonal cycles of sun, wind, and rain to provide natural heating and cooling primarily from passive (free!) sources.  Her clients enjoy an average 75% reduction in total energy usage compared to conventional buildings.  She uses a palette of building materials that ensure healthy indoor spaces and minimal environmental impact.

For more articles like this, visit us online at and contact us if you have a natural building topic you would like to see covered.

Thank you for reading!

Down to Earth Design

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Fawn Grove, PA    17321  |  215-540-2694 (PA)

copyright ©2015 Sigi Koko dba Down to Earth Design