Building with earth is an ancient art.  It can be done as skillfully and scientifically, or as simply and dreamily, as a person can imagine.

The method we use in most of our projects is known as cob, monolithic adobe, or more specifically the Oregon Cob method.  In areas where earthen building traditions are alive and well, it is a great idea to work with an experienced local builder.  But if there are no living traditions in your area, the Oregon Cob method can help you create an effective method in a relatively short time.

Good building dirt is bad garden dirt, and vice versa.  For a good earthen project, you want subsoil (the lighter or single-color layer underneath the dark brown topsoil); and you want mostly hard grit, sand, and sticky clay - not the soft, velvety silts and loams that make fluffy garden tilth. 

For our typical earthen building projects, here are roughly the amounts of materials involved. 

Rocket Mass Heater

Annex6 Rocket Mass Heater

Base: Compacted gravel, 4" concrete slab, or reinforced floor suitable for waterbed / garage storage.

3-5 yards sand (or local sandy subsoil)
1-2 yards clay dirt (or about 30 gallons ceramic clay)
Straw - 1 bale
Bricks - 80+ depending on configuration. 
For our favorite J-shaped firebox for an 8" ID system,
- 50 skinny half-firebricks (1.25" x 9" x 4.5") and
- 70 full-size fire brick (2.5" x 9" x 4.5"),
- cut two of the full-size brick to 7" long

Perlite - 2 to 6 cu ft.
DuraBlanket about 12 feet x 24" x 1", or rock wool x 2"
Wire mesh "hardware cloth", 1/4" mesh, 48" by 60"
Ducting or stovepipe - 20 to 40 feet or more, with elbows and Ts, to fit the bench layout and chimney connection.

Barrel - 55 gallon or 30-35 gallon drum
(Matching barrel for manifold, or 70 more bricks)
(Feed tube barrel- we typically omit this, but it's in the original book's list)
Rubble or rock for infill / facing - up to volume of project.

Firewood (with hatchet or ax if needed)


Shovels / spades
Buckets (5 gallon) - at least 5, 15 to 20 if available.
Tarps for mixing cob (roughly 8' x 10') - 3 tarps
Large paintbrushes / sponges
Tinsnips - 1 pair for every 2 participants
Crimpers if available, or pliers, for crimping ducting
Grinder, hacksaw, or plasma cutter for metal-cutting
Tile saw, brick-sets, or other methods for cutting 2 firebrick to 7" long
Masonry trowels, floats, any other masonry tools.

Level (aluminum or steel, 24" to 48", for muddy work)

For demonstrations:

Extra bricks
Extra firewood
Extra metal buckets and stovepipe
Sand pit or fire circle (6' radius of level, bare ground)
(Digital projection valuable but not necessary)
Large paper or cardboard for template
Chalkboard or big paper for ‘Burning Questions’ board

Earthen Oven

Frog Oven

Painted Frog
Stout Base (wood table or masonry plinth)

Perlite or other suitable insulation (4-8 cu ft)
Bricks - about 30 to 60 depending on oven size and design
Sand - about 2-3 cubic yards (or sandy subsoil)
Clay soil - about 1 yard, or 20 gal of pottery clay
Newspaper or plastic wrap to cover dome
Straw (1/2 bale, or a full bale if using for main insulation)
Stovepipe: 15 cm or larger diameter, at least 1 60cm length (ideally, pipe and fittings to 60 cm above roof).

Optional: Lime, clay pigments, mica, or other decorative materials.


Shovels / spades
Buckets  - at least 3, up to 10 is helpful
Tarps for mixing cob (roughly 2m x 3m)
Large paintbrushes / sponges
Tinsnips for adjusting chimney heights
Masonry trowels / floats / any available plaster or brick-and-mortar tools (cold chisels, scrapers, brick sets, etc).

(Other tools as needed for construction of table or plinth - hammers, saws, screwdrivers)

For demonstrations:

A length of chain or rope if available (approx. 2 meters)
Large piece(s) of cardboard
Easel or wall for ‘Burning Questions’ board
Bricks and earthen materials as above.