Adobe-Hemp Casita Project Cont.

Figure 10. Workshop 1, Preparing mix for Cinva Ram Press

Continued from Home page.

The second workshop was held in late August. It was advertised in social media yielding ten participants. The workshop required payment to help with the expenses of building the structure and to cover the cost of a community meal, camping spots, lectures and hands-on demonstrations of hemp processing, CEB making and earth construction technologies.  The workshop group was helpful in the manufacture of a small amount of CEB’s. Due to time constraints and a full schedule of events the workshop was of greater value to the participants than to producing large quantities of CEB’s. The second group was very diverse, with the majority being women working on projects in agriculture, youth, and textiles (Figure 11)

Figure 11. Second Workshop Group

After the workshop, work continued on the vaulted roof construction. Again, the process is tedious involving hauling the blocks, preparing the mortar, laying the blocks while working on scaffolds. Similar to adobe wall construction, three to four layers are laid daily. The mortar used was a commercial mix of lime, cement and sand. Although the blocks varied in different combinations of raw ingredients, they were all infused with the hemp hurd derived from Rezolana Farm. The construction of the vaulted roof took place over several weeks. A typical day of work is about six hours laying three courses of blocks on each side of the vault. The blocks were laid on top of the concrete bond beam with the lime cement mortar. This mortar will provide greater strength in bonding the blocks and providing an impermeable layer to resist water infiltration. Construction continued from the bottom to the peak. Once the vault was completed it was coated with a layer of cement based stucco imbedded in a fiberglass mesh (Figure 13). A final layer of cement based colored stucco was applied completing the roof vault construction. Upon completion of the exterior vault work the interior support forms are dismantled  exposing the CEB’s.

Figure 12. Applying Stucco Coating

Interior and Exterior Finishes

With the completion of the basic shell, the next step is to finish enclosing the space and protecting from the elements of nature. The south and north window frames are fitted with double pane units made at a local glass company in Alamosa. The east window is a double hung awning window. At the top of the east end of the vault roof there is a 12” square window for light and ventilation. The doorway was fitted with a site-built door made out of 1” rough lumber and hung with large strap hinges.

The interior walls and vault are plastered with a base coat of mud plaster, followed by a secondary thin coat to seal the cracks. The final finish is a slurry made of dry  milk, rice flour and fine clay. A two  inch slab of mud and hemp hurd will be poured on the floor to cover the concrete surface.

The exterior walls are coated with a mud plaster base coat followed by additional layers of plaster as necessary to seal the cracks and seal the surface of the wall. The mud plaster is not impervious to water so the walls will have to be re-plastered on an annual basis (Figure 13).

Figure 13 Completed Casita

Project Summary

Overall the design and construction of the Casita was a success. It served to illustrate the use of hemp hurd for bricks, floor slab, and finish plasters. In rural areas where agriculture is possible hemp can be cultivated and used for a variety of applications with the waste hurd utilized for making bricks and finishes.

The project was a total educational experience  for the apprentice, workshop participants and general public interested in the earth building technologies. The use of local sources of materials kept the embodied energy low while reflecting a local vernacular design coupled with the ancient building traditions of roof vaults.

Yet to be completed are the earth floor slab, final interior and exterior finishes, Photovoltaic Panel Connection and rainwater catchment gutter.

 Design Guidelines

The goal of this small building is to illustrate that locally available materials can be utilized in addressing sustainable, low embodied energy, and culturally relevant design. The design will utilize hemp hurd for the CEB’s, earth plasters and floor slab.

* Culturally Relevant Regional Design

Pueblo Revival, middle eastern(vault), local vernacular

New Mexico State Adobe Building Code Compliance

Starter or core unit, possibility for expansion of scale

 * Locally Available, Low embodied Energy Building Materials

Recycled Adobe Bricks & Concrete Slab

Rough Sawn Lumber, Local Sand & gravel

Locally Grown Industrial Hemp-Compressed Earth Blocks

* Climate Sensitive Ecological Design

Buffering Climate Change/temperature swings

Passive Solar Gain/Thermal Mass-earth walls, barrel vault

Rain Water Catchment

Photovoltaics for electrical needs

* Educational Outreach

Training for adobe apprentice

Public Workshops

Documentation of process/Availability of building plans

Building Tours

Thermal Performance Monitoring

* Proto Type Structure to address:

Affordable Micro-Housing/Homeless Population

Agricultural Applications

Creative arts

Healing/spiritual needs

Native American Housing

Acknowledgements

I would like to thank Rebecca Burgess of  Fibershed for funding and support throughout the project and over our many years of collaboration growing and processing hemp. Also, without the help and youthful energy of Jonah Jenkins, my adobe apprentice, I would of not been able to build the casita. His assistance and network connections were invaluable and key to the outcome of the project. Finally my gratitude goes to all of the workshop participants who contributed labor and left their imprints on the building.

The following list itemizes the materials and time for the building of the Casita:

Materials:

Recycled  10” X 14” X 4” Traditional Adobes (525 blocks)

Locally available clay

Locally available sand & Gravel for concrete bond beam

Locally available clay for CEB

Rough sawn lumber for frames and overhead beams from local saw mills.

Labor:

Transporting Adobes:  46 hours

Wall Construction: 174 hours

CEB Production:76 hours

Barrel Vault Roof Construction: sealing : 82 hours

Interior & Exterior Mud Plaster: 24 hours

Earthen Floor: TBD

Window & Door Installation/finish: 12 hours

Corner Fireplace: TBD

Total Labor: 414 hours

Estimated Cost of Materials: $4,000