Rethink Your Life!
Finance, health, lifestyle, environment, philosophy
The Work of Art and The Art of Work
Kiko Denzer on Art

[Cob] Earthen Oven Questions

Bernhard Masterson bernhard_masterson at
Tue Jun 3 10:38:34 CDT 2008

Hi Tim,
   I have built several earthen ovens and have the following thoughts on your questions.   I assume you are considering an oven 48" deep and 20" wide.  Such a shape will make accessing bread, pots, etc. in the back of the oven quite difficult.  Anything deeper what you can easily reach with your arm begins to be troublesome.  Oblong ovens tend to work better with a wider and shallower floor shape.  Round or close to round is indeed preferred for ease of access and maybe cleaner burn although I am not sure on the last point.
    A cardboard barrel may work for a form.  But I would recommend a sand form.  A sand dome will be create a stronger more uniform shape that holds up to the thermal movement better because the stresses of movement are evenly dispersed throughout the structure.  (Corners and edges concentrate stress.)
    I would advise against using any metal in the oven dome because it has a different thermal expansion coefficient than the clay masonry and will eventually break apart your oven.
    If you are making a long deep oven I would recommend no chimney or a rear chimney even though it is more complicated and difficult to seal off once the firing is complete.  A front chimney slightly increases the distance one must reach into the oven and could compound the challenges of access with a deep oven.
    I'll be teaching an earth oven workshop Aug. 23-24 in Washington if you are interested in getting hands -on experience.

- Bernhard 

____________________________________bernhard_masterson at

Natural building instruction and consultation

Date: Thu, 29 May 2008 08:05:17 -0500
From: "Tim Reese" <TReese at>
Subject: [Cob] Earthen Oven Questions

 I am in process of planning an earthen oven and have a few questions.
Shape: I am considering a 48" by  20" rectangular shaped oven because of
the space & base style.  After reading K. Denzlers book, round seems to
be preferred.  Does a rounder oven function significantly better than
Form: I am considering using a cardboard barrel and wire mesh as form to
attach the cob to rather than sand.  I just feel a little more confident
about it not falling apart if I use some wire mesh.  Anybody have
experience or reasons this isn't a good idea?
Chimney: With a rectangular oven, I am planning a rear chimney that
would be open for firing, but then sealed up.  Denzler recommends a
front chimney, but with a more rectangular design I am wondering if that
will work. Any thoughts?
Tim Reese
Gale Woods Farm Supervisor
Three Rivers Park District
7210 County Rd 110 West
Minnetrista, MN 55364
(763) 694-2002 office
(612) 490-2186 cell
(952) 472-9205 fax

It’s easy to add contacts from Facebook and other social sites through Windows Live™ Messenger. Learn how.