Project Background

CCAT is building a tool shed with green methods in mind so it is called the green shed. Part of this green design is the walls that will be made from as many natural or recycled materials as is reasonable. This project offers students the opportunity to get hands-on experience with various wall infill methods and materials.

The concrete foundation of the green shed was poured to make a standard 6 inch wide wall. This is not wide enough for most earth building methods to be of much insulation value. The foundation for the walls will have to be widened to accommodate.

The frequently wet nature of our climate may present other obstacles. The water soluble nature of many natural materials will be considered in material selection. Some methods using organic matter present the issue of rotting. The tendency of organic matter to rot in out wet climate will require the walls to "breathe" well so as to not trap moisture inside.

An existing example of natural wall construction exists at CCAT http://www.appropedia.org/CCAT_natural_wall_constructionThere is an example of papercrete and of straw and clay-slip. It may yet be used for inspiration on the insulation walls. Cob and cordwood are also being considered.


Project Members

Garrett Duffy and Marqes Mayo

Project Definition

The north wall will be another example and experiment in natural building. Insulation will be one functonal motive but also keeping in mind that this wall is for a tool shed. This wall will be designed to hang tools on in some way. The natural bulding technique known as cordwood fits the demand for insulation and offers future builder the opportunity to mount hooks for tools.

Literature review

Garrett's sources

 Books

• Callahan, Tim, and Clarke Snell. Building Green: A Complete How-To Guide to Alternative Building Methods Earth Plaster * Straw Bale * Cordwood * Cob * Living Roofs. New York: Lark Books, 2005. Print.

This book offers a fairly solid overview of the listed building methods. For cordwood it warns against various errors the experts have made, such as using hardwoods and sealing the wood ends.

• Chiras, Daniel D.. The Natural House: A Complete Guide to Healthy, Energy-Efficient, Environmental Homes. White River Junction: Chelsea Green, 2000. Print.

"The natural house" goes into more detail about actual construction and foundation considerations.

• Cordwood Building: The State of the Art (Natural Building Series). Gabriola Island, BC: New Society Publishers, 2003. Print.

This book is by far the most comprehensive book found so far and is exclusively about cordwood construction. It details mortar mixtures, wood types, wall types and some advanced methods.

Journal

• Pierquet, Patrick , Jim Bowyer, and Pat Huelman. "Thermal performance and embodied energy of cold climate wall system." Forest Products Journal 48.6 (1998): 53. ProQuest. Web. 13 Feb. 2010.

The concern of this article is the thermal performance of twelve building methods and their embodied energy. Two of methods of relevance to this project are 2x4 construction and cordwood for the sake of comparison.

 Websites

Stankevitz, Alan. "DayCreek Journal - June 25, 2000." Daycreek Home Page. N.p., n.d. Web. 13 Feb. 2010. <http://daycreek.com/dc/HTML/journal062500.htm>

The above site has a responsive forum for those who have cordwood questions.

"Cordwood." Chaetreuse. N.p., n.d. Web. 13 Feb. 2010. www.brightgreenresearch.org/images/pdf/2009.11.02_MaterialConcept_Cordwood.pdf

This page reports some information about cordwood, such as R values and compressive strength of mortar mixes.

So what is cordwood?

Cordwood is among the several common natural building methods. Firewood is often sold in a unit known as a cord. Such woods are at times a suitable bulding material. The more durable softwoods tend to be best. Logs that are at least 12" long are secured in to the wall with a mortar of sorts. The lengths of the logs are mounted perpendicular to the wall itself. The mortar may be made with concrete, cob, or even paper crete. The plan of this project is to use western red cedar logs and mortar made from portland cement, sand, lime and wet saw dust.
The stability of the mortar is very important. Shrinkage of the wood or the mortar is to be avoided as best as one can. The mix suggested by cordwood expert Rob Roy, author of "Cordwood building: State of the Art," has the strange ingredient of wet saw dust. It acts to slow the drying of the mortar. This helps to prevent cracks and gaps between the logs and the mortar.

Mortar Testing

As mentioned above soaked saw dust is mixed into the mortar to slow the drying process. We are also experimenting with soaked newspaper and office paper. Also not all sawdust is the same. Some of our tests include sawdust passed through a 1/2 inch screen and other through a 1/4 inch screen. The concern is that if the saw dust id to large it may make a crumbly mortar and if it is too small it will not store enough moisture. Hardwood saw dust should be avoided as it makes a crumbly and difficult to work mortar. (Roy 28)

Criteria

Criteria Constraints Weight
Maintainability Repairs expected less than once per year. 8
Long lasting At least 8 years expected 7
Appropriateness for tool shed Can accept at least one shelf 4
Tolerance to wet climate Not expected to mold or rot 9
Ease of getting materials Most materials acquired in Humboldt bay region 8
Ease of building Done with unskilled labor 7
Thickness Less than 12 inches 10
Insulation R-value comparable to standard construction 7
Durability Can withstand minor abuse 8
Use of recycled materials Substantially less embodied energy than standard construction 9
Cost Less than $300 10

Consideration: potential for the wall as an education tool in green-building

Materials and Retail Costs

Quantity Material Source Cost ($) Total ($)
3 94 lb bags portland cement Pierson Building Center 0.00 0.00
0.5 cubic yard of masonry sand Eureka sand and gravel 0.00 0.00
4.5 cubic feet of saw dust no provider yet 0.00 0.00
4 50 lb bag of hydrated lime Do-it-best hardware 8.50 at discount 34.00
0.25 cord of Western red cedar Almquist Lumber 300.00 81.00
Total Cost $184.00

Tools to be barrowed from CCAT


shovels
wheel barrow
chain saw
hand saw
trowels
garden hoe
drawknife
splitting wedge
sledge hammer
axe
measuring tape

Proposed Time Line


3/5/10-pick up sand and sawdust samples (sawdust will have to tested to determine suitability)
3/5/10-get wood delivered
3/6/10-make at least 4 test samples of mortar. (We need to test the effectiveness of the cement retardant and appropriate water ratio)
3/8/10-see which test sample have dried. Scratch and them break the dry ones to test for durability.
3/12/10-make more test samples. Failure of all previous sample is a possibility.
3/12/10-saw several of the logs to right length and split into quarters. Let them dry some over spring break.
3/22/10-We hope to have determined the right mortar recipe by this time. If so about 4.5 cubic yards of the right sawdust or paper will be picked up.
4/2/10-lay down the first and maybe second layer of cordwood and mortar. Split wood for next week
4/9/10-keep laying cordwood.
4/16/10-keep laying cordwood.
4/23/10-finish here.

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