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Our project as of May 10, 2010.


Background

The Arcata Educational Farm has been operating as a CSA (Community-Supported Agriculture establishment) in Arcata, California since 1993. This farm allows students, residents, and local farmers to work side-by-side in their efforts to accomplish goals such as sustainable agriculture and valuable work experience. The farm also allows fresh organic produce to be sold as shares to stockholders and members of the organization.

As students enrolled in the ENGR305 class, we decided to build an earthen informational kiosk at the entrance of the farm. The earthen wall will be constructed with a cobb base, and will than be coated with an earthen plaster finish. The kiosk will serve not only as an entrance piece to the farm, but also as a place to learn about current and past projects constructed at this site. Projects such as the AEF solar water heater , or the AEF spiral herb garden.

Opportunity Definition

Who
Luke Pedersen and Andrew Spickerman are working with the Arcata Educational Farm.
What
The project is to build an earthen kiosk at the entrance of the garden.
When
The informational kiosk will take approximately fifteen weeks to complete and will be finished by May 15th, 2010.
Where
930 Old Arcata Road
Arcata, CA 95521
Why
The practical purposes of this wall would be to serve as an entrance piece and as a place to obtain infromation about the farm. Most importantly it would serve as an educational tool based at the farm.

Literature Review

Cobb Wall concerns

Rain and moisture is extremely detrimental to earthen ovens, and due to this oven’s location in a relatively moist climate, keeping the oven dry is one of our main concerns. A roof will have to be built over it before we finish, and we recommend a fire be built inside of it once a month to keep it from cracking. The drying process is another concern. If a fire is built inside too soon the oven will dry un-evenly and cracking will likely occur. [1][2]

ED: NORMALLY YOU WOULD KEEP ALL DESIGN DECISIONS AND EDITORIALIZING. YOU DON'T NEED TO CHANGE IT, BUT THOSE DECISIONS AND SUGGESTIONS WOULD BE BETTER PLACED LATER, REFERENCING THE LITERATURE FROM THE BODY OF THE SPECIFICATION PART OF THIS DOCUMENT.

Gathering Materials

It is a good idea to use as many on-site or near-by materials as possible when working with cobb. Cobb requires a vast amount of materials that are very labor and time intensive to acquire. Here is a list of the materials you will need:

  • Water and a way to transport it to the construction site
  • Clay, Sand, and Straw which are the key building materials used for cobb
  • Foundation: Cement, Stone, and Mortar are examples of what can be used
  • A reliable Vehicle to transport materials
  • Roofing to protect the wall from the elements: A variety of different types of roofing can be used
  • Tarps to mix your cob
  • Multipurpose buckets: The more the better
  • Carpentry tools such as hammers, nails, screws, levels, measuring tape, etc.
  • Earth moving tools such as shovels and wheel barrels
  • Plastering tools and materials: horse or cow manure, clays with pigment, trowels, and smoothing tools such as paint brushes
  • Lots of friends to help build[3]


Testing

The jar on the left has settled out, and the jar on the right was recently shaken.

Testing Clay Content: The soil shake test is used to determine how much clay is in the makeup of the soil.

Building a foundation

There are several key items that the book goes over when it comes to laying a strong foundation. It begins with the layout which is essentially the placement of the proposed object. The second step is the trenching phase. The most important aspect of trenching is that the poured foundations or footing surfaces are level. The third stage is to reinforce the foundation after the first wall or pour has dried. The final stage is the finishing process, which calls for smoothing of the foundation surface, allows for further building.[4]

Criteria

These are the most heavily weighted criteria. We weighted each criteria on a 1-10 scale, based on importantance, with 10 being the highest.

Criteria, Constraints, and Weights for the Arcata Educational Farm Earthen Oven
Criteria Constraint Weight
Cost We would like this project to cost no more than $200 dollars 5
Aesthetics We want this to be a symbol of pride for the farm since it is at the immediate entrance 4
Educational Value It must have enough space to post as many informational documents as possible 10
Maintainability The wall must be strong and require very little maintenance (<1 hour) on an yearly basis 7
Sustainability The use of common, local, and low impact materials 5
Durability We want this wall to stand for atleast ten to fifteen years 10

Additional Considerations

  • Color
  • Glass enclosurement to protect information pamphlets
  • Simple frame and roof design
  • Six-foot frame with five feet of earthen wall

Costs

There are a multitude of ways to construct an earthen kiosk. The wall itself will use a cob building technique which is primarily made of earthen materials. Much of this earthen material was acquired at the Arcata Educational Farm instead of purchasing them from a store. Gathering on-site materials will greatly reduce the price of constructing an earthen wall. A large portion of the overall cost will be associated with building the support frame, roof, and foundation. Donated or salvaged goods are a good way to reduce the total overall spending.

Quantity Material Source Cost ($) Total ($)
1 2" C-clamp Arcata Lumber 2.29 2.29
1 Rice Straw Bale Three G's Hay & Grain 6.75 7.34
9 cubic feet Crushed Rock Eureka Ready Mix Donated 0
About 6 Gallons Gasoline (transportation) Shell Gas 3.25 20.00
6 80-lb. Concrete Ready Mix Bags Arcata Lumber 4.99 29.94
1 2x4 Fir Post Arcata Lumber 2.24 2.24
Lots Clay On-Site 0 0
Lots Sand On-Site 0 0
1 4x8 Plywood Board Arcata Lumber 11.99 11.99
1 Claw Hammer Ace Hardware 8.99 8.99
1 Measuring Tape Ace Hardware 5.49 5.49
1 9" Level Ace Hardware 4.29 4.29
6 1x6x6 Cedar Panels Arcata Lumber 1.99 11.94
3 4x4 Fir Post Arcata Lumber 8.32 24.96
Lots Nails Arcata Lumber Various Prices For Various Sizes 11.18
.5 lbs Screws Arcata Lumber 2.59/pound 1.35
2 Post-Base Attachments Arcata Lumber 5.29 10.58
3 50-lb Fence Post Mix Arcata Lumber 2.99 8.97
Total Cost $161.55

Project Timeline

This timeline was designed during the early stages of this project to keep us on a timeline that would allow us to finish the kiosk on time

ITEM PROPOSED DATE DATE MET?
Obtain all materials 4/09/10 Completed
Lay Gravel 4/09/10 Completed
Construct foundation 4/12/10 Completed
Begin cob construction 4/16/10 Completed
Begin roof construction 4/16/10 Completed
Finish all construction 5/10/10 Not Yet

References

  1. Augier, F., W. J. Coumans, A. Hugget, and E. F. Kaasschieter. "On the risk of cracking in clay drying." Science Direct - Chemical and Engineering Journal 86.1-2 (2002): 133-38. Web. 13 Feb. 2010.
  2. Denzer, Kiko `. Build Your Own Earth Oven. N.p.: n.p., 2000. Print.
  3. Bee, Becky. The Cob Builders Handbook. Grove City, PA: Jenkins Publishing, 1997. 13-14. Print.
  4. Jordan, Robert. Masonry. Wilmette, Illinois: Frederick J. Drake & Co, 1955.
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