Addition to a Cob Studio
by Kristina and Reid

We will build a small extension to our cob studio using earthbags.  We decided to use earthbags as cob is not a good choice for building during freezing temperatures.  The purpose of our small extension is to create a wind break for our entry door into our studio.  We also want to use a small space for a bath area.  The extension will start from the northwest wall of our studio and extend to cover the westside.  We will enclose the south with glass to allow solar gain in for warmth.

Brei helps Kristina with our earthbag walls.

We will use the book "Building with Earth" written by Paulina Wojciechowska to help us with this project. 

Earthbag Extension Cost:
miss-printed rice bags $200
barbed-wire= $40
rebar (20ft)=$4.50x10=$45
galvanized wire = $40

Current Total = $325

Building with earthbags was relatively simple.  Our extension wall was a partial "u" extending out from our existing cobstructure.  The "u" shape with "opening" facing the south made our extension look a lot like the "u" shape modules of Mike Reynolds' rammed tire earthships.  Because of this you will notice similarities of our construction methods with that of "earthships".  

The foundation is formed using earthbags filled with gravel.

Kristina levels out dug out section.

Reid fills bags with gravel.

First course of earthbags.

Earthbag Walls

Kristina "tamping" down bag securely on foundation.

Once we completed the earthbag foundation using bags filled with gravel, we continued stacking earthbags filled with dirt. When the desired wall high is attained we will secure the top with a rebar-reinforced  concrete bond-beam.

Installing window framing.

Kristina pounds bag in place.

Lintels placed over frame to support bags.

Brei and Kristina securing bags in place.

constructing bond beams

Our earthbag extension required two separate bond beams.  The first bond beam was required to stabilize and secure the main "curved" earthbag wall.  This first bond beam is similar to the type of concrete bond beam used for adobe walls.  However, since our wall was curved rather than constructing forms from "rigid" lumber, we used "flexible" 1/8" thick masonite.  The masonite was was tied to #3 rebar spiked into the earthbags. Our second bond beam was required to secure the earthbags and support the windows of the south facing section.  Since this section was straight and not curved, we used 2x4s for forms. 

Although the curved earthbag wall provides sufficient support of roof, posts were required at a couple of locations to secure "extension" beams that were "spliced" to the beams of our original cob structure.

securing extension beams on bond beam

bond beam for south-facing window

1"x6" rough-cut ceiling boards were nailed over the extension beams.

Covering bags with earthen plaster.


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