The plaster story started almost a year ago when the installation of the chicken wire lathe on the structures began. This week, David Kaiser Jr., owner of Elite Plastering and his crew are wrapping up the final stages of the exterior, lime plaster. It has been a long process. Hand plastering and the preparation for plastering is time consuming but the extended lapse of time from start to finish is more indicative of the challenges of custom building, especially within the criteria of the Living Building Challenge. That time reflects waiting, weather, and the sequence of other pieces in the construction puzzle. David did not want to take the risk of cracks during the curing time frame due to impact on the structure while other trades were completing their work.
Once the chicken wire is in place the plastering can begin. With anticipation, the structures were draped in a plastic tent in December 2012. The covering allows for humidity and temperature control during the curing process.
David Kaiser developed his own lime plaster recipe for the Desert Rain project. All the materials; lime, clay, and sand, come from locations close to home – Deschutes River Woods, Prineville, and Washington state. The lime based plaster formula is based on the traditional mixes that were used during the Roman Empire. The use of lime in plastering applications dates back to the construction of Egyptian pyramids about 4000 B.C. It has since been refined and has found a place in green building applications.
Lime finishes, naturally high in pH, create an anti-bacterial surface neutralizing the development of organic substances such as mold and fungus. It is a breathable material that allows water vapor to permeate freely so moisture evaporates quickly. Roman plaster and slaked lime products absorb carbon monoxide from the atmosphere to chemically change it into limestone. This reaction not only increases the strength of plaster over time but has a great environmental benefit. Roughly, every 100 pounds of lime that is used will absorb approximately the same amount of CO2 that a tree does in a one year period. Lime may be beneficial in absorbing other toxins as well, passively removing them toward the outside environment.
The plaster at Desert Rain is a three coat process with the color being added to the final layer. Work began on the accessory dwelling unit. The first coat contains straw that acts as a binder to help the plaster adhere to the wire lathe. The layering process aids the curing process and creates consistency in the appearance and coverage.
A side note to the plaster story: Barb and Tom have set a guideline that everyone who works on the Desert Rain project must attend a Living Building Challenge presentation so they are aware of the scope of the project, the restrictions, and the goals. If contractors and subs cannot attend a live presentation they watch a video. Barb visited with the Elite Plastering crew. Comprised of mostly Hispanic workers, some with limited English, Barb was concerned they may have had difficulty comprehending the Living Building Challenge points and petals. As a result, the Desert Rain project will soon have a Living Building Challenge presentation video available in Spanish.
The final coat of plaster contains the color coat. The initial mix was applied to one of wall of the ADU as a trial. After drying, it wasn’t quite the color that was anticipated. With some tweaking of the tints, a color was approved and the plastering continued.
With the weather heating up this past week, the plastic sheeting has been rolled up revealing the final layers of plaster on Desert Rain. After a year of anticipation – the lime plaster exterior will soon be finished.
The plastering process has been an on-going story for most of a year. The initial chapter began July 2012, CLICK HERE to read more about the process and the product. The last walls will soon be covered in plaster. In two to three weeks curing time, Desert Rain will be unwrapped, revealed and finally – plastered!