Double-Chamber Earthen Ovens

The smoke chamber helps the oven burn cleaner, keeps any remaining smoke away from the baker's face, and still provides a very traditional dome heat for artisan baking, roasting, and broiling. 

Current Workshops

Natural Building Topics:

Rocket Stoves

Two-Chamber Cob Oven

Earthen Materials,

Cob and Cob/Bale

Paints and Pigments

Fire Science

Foundations and Drainage

Greenhouses and Rainwater Gardens

(no, we haven't tried to make one out of cob.... yet...)

Drafting, Design,  Writing and Illustration

Conventional building / code considerations

A traditional earthen dome oven is a lovely object, that makes even lovelier food.  Heat from a wood fire soaks into the gently curving walls, raising the temperature up to 800 or 900 degrees Fahrenheit before baking begins. 
The fire is raked out, the floor swabbed clean with a damp rag, and after a few minutes to 'soak' the heat evenly throughout, the baking begins.  Cracker-crust pizza, flat breads, artisan loaves, fluffy scones and biscuits, pies, cakes, brownies, roasts of meat or veggies, a quick refueling with wood chip to smoke and broil some late-night chicken; then another soak, and the last heat used for gently steaming pots of bread pudding, yoghurt cultures, and raising the dough for tomorrow's treats.

The main costs of a traditional dome oven are time, labor, and fuel.  Simple domes can be built with on-site or local materials such as sand, clay, and straw.  They can be returned to the earth once their useful life is finished (after too many cracks appear in the dome, or the baker moves on to other pastimes).

A traditional dome oven:
The main troubles with the traditional dome are smoke pollution, and the associated inefficiency (they use so much fuel that deforestation is a concern in many areas where they are built for single-family use).

Many modern citizens, the baker included, prefer clean air to even the most fragrant of smoke. 

Both the smoke and the efficiency can be addressed with one basic change: adding a chimney, with a smoke chamber and air-inlet door that give the flames a more effective balance of air and heat for a cleaner burn.

Professional wood-fired ovens naturally include a chimney, but mounting this chimney on a traditional dome has puzzled many home builders. 

We've seen chimneys in the top of the dome (leaks heat throughout the baking cycle), with a smoke visor that wraps over the top, or hidden in back. 
Our double-chamber method is relatively simple for novices to build, improves the efficiency of the fire's burn, and does not involve any hidden parts or dampers to break or clean.

Our double-chamber oven has two doors.  The burn door is in front (allows air in during the burn cycle, and smoke up the chimney.  The bake door is located further in, to trap heat in the dome during baking, exactly like a traditional single-dome oven. 

The only other improvement we recommend is more careful layering, including a thick layer of perlite insulation.  It costs a little more than straw, but insulates far more effectively.  And it can also be recycled into the garden when the useful life of the oven is over.  We use a nice earthen plaster mix inside, and any suitable cob,  earthen plaster, or lime plaster on the outside.
Fire in Frog Frog Oven almost dry
Frog Oven (Portland, OR)

Other double-chamber oven designs we've helped with:
Ujima Center Snail Oven

Harmony Fields oven
Harmony Fields Oven

Ovens using similar layout, by other builders:
Lessons Patrick learned

Our double-chamber oven plans are available in PDF.
We also recommend Kiko Denzer's book, "Build Your Own Earth Oven," published by Handprint Press.  It describes the traditional dome oven, some lovely artistic variations over years of experience, plus artisan bread recipes.