Plaster prep work has been going on for the past few weeks at Desert Rain. The crew from Elite Plastering was working on installing chicken wire wrap the day I talked with them about the plastering trade. Elite Plastering is a family owned and operated business. David Kaiser Sr. has been in the plastering business for 35 years. David Jr. started out helping his Dad when he was little more than a kid. For the past 17 years, he has been working full-time in the plastering trade. Brother, Bill is in sales and marketing. They both chuckled that he was out on the golf course that day.
Preparing the exterior walls for plaster requires installing lathe. Chicken wire is the material of choice in this application. It is wrapped and stapled over the exterior sheathing and the house wrap that has been previously installed on the structure. The chicken wire provides a surface on which the base or ‘scratch’ coat of plaster can adhere. It is a time-consuming process as the wire must be fitted around windows, doors, and framing obstacles. When the chicken wire wrapping is completed, the plastering can begin. It is common to use up to three layers of plaster for an exterior application. The final layer often contains a tint . The Kaisers and crew will be hand plastering. Having worked on a plastering crew for three strawbale projects, I am extremely appreciative of the skill and labor intensity of hand plastering.
The Kaisers use a lime based plaster formula that David Jr. developed, 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. The Greeks and Romans refined the process. Marmorino or Roman plaster was used as a finish wall surface on Roman lime cement. Applied 10 centimeters up a wall, it permitted the absorption of mineral salts from humid walls that contacted the ground, to provide transfer of moisture to the outside.
This maintained breathability and structural stability. Roman plaster can withstand centuries of moisture when applied to external or internal wall surfaces. Early plasters might contain lime, gypsum, marble dust, fibers and sand in up to three coats. Prior to 1900, lime was used for all three coats of the plaster system. These early plaster formulas often included hair or fibers as well. More modern exterior plasters, often called stucco, may contain keene’s cement or portland cement added to the lime-based basecoats to strengthen that initial coat. Proportions of cement and lime may be varied with each layer to provide a strong base and a flexible finished surface.
The Elite Plastering team has been learning new ways to provide plaster installations that portray beauty and feeling, but are also, durable, non-toxic and green. Lime finishes, naturally high in pH, create an anti-bacterial surface. This surface neutralizes 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.
With the prep and lathe work nearing completion, Desert Rain will soon be getting the first coat of lime based exterior plaster. The plaster formula will be as traditional as the plasters of the Roman Empire. The prep work for plastering has been time-consuming. The hand plastering will be time-consuming. As the cliché and history tell us, ‘Rome wasn’t built in a day’. Desert Rain is not being built in a day either, but in the pioneering, pursuit of ‘extreme green’, Desert Rain is using history to make history.