“Earthen architecture” seems a grandiose term for the aspiring adoberos who were flinging mud at Pima County’s Canoa Ranch the other day.

The term seems less than adequate, however, to describe the historic and stunningly beautiful Spanish mission churches at Tumacácori and San Xavier or the 650-year-old, four-story ruins at Casa Grande.

Last week, a traveling band of national park preservationists and students learned the skills of making, building and preserving mud-based structures — and applied those skills in conservation projects at the Canoa and Empire ranches, the mission at Tumacácori and the presidio at Tubac.

“Earthen architecture composes a vast majority of the vernacular architecture in the world,” said architectural historian R. Brooks Jeffery. “It’s the most commonly used material, because it is the most readily available.”

It is also extremely vulnerable — and techniques for preserving and restoring it need to be preserved as well, Jeffery said.

He said the International Workshop on the Conservation and Restoration of Earthen Architecture (known by its Spanish acronym of TICRAT) seeks to elevate the humble building material and its craftsmen.

“The purpose really is twofold: valorizing adobe architecture. The buildings created of earth are equally valuable to those created of stone or any other material. The second is revalorizing the traditional craftsmen skills that produce it. In Mexico, they still valorize masons and adoberos. Here in the U.S., not so much.”

Needed Skills

Jeffery is director of the University of Arizona’s Drachman Institute, the outreach arm of the College of Architecture Planning and Landscape Architecture, which coordinated the workshop. The workshops have been organized since 1994 by the U.S. National Park Service and Mexico’s Instituto Nacional de Antropología e Historia (INAH).

Part of the reason for creating the partnership was a realization that park preservationists had specific skills that needed to be shared and that those with the skills were an aging group, said David Yubeta, who ran preservation programs at Tumacácori National Historical Park for 27 years until his retirement.

“The average age of restoration workers in the Park Service was 55,” said Yubeta, “We wanted a forum to talk to each other and learn what technologies we’ve all come up with.”

Training the next generation of preservationists is critical, he said. This year’s workshop was attended by 20 college students from six universities, in addition to park managers and preservationists in Mexico and the United States.

Sarah Redden, who is pursuing her master’s degree in historic preservation at Columbia University, said the workshop was an escape from “a little bubble of learning about New York City architecture.”

“I didn’t know anything about earthen architecture or adobe,” she said.

Gabrielle Miller, who is working on a certificate in heritage conservation at the University of Arizona, said she was familiar with earthen architecture but appreciated the opportunity get her hands dirty actually making it.

“Sometimes, in the classroom, you become a really good writer, but you miss out on being able to connect to things — to learn and to do the hands-on stuff,” she said.

Daniel Olvera, from the Baja California capital of Mexicali, is working on his doctorate in architecture at Universidad de Colima. He said he learned many techniques he can bring to his students in building construction and repair.

His research involves figuring out why some adobe buildings in Mexicali survive earthquakes, while others crumble. It’s partially the method of construction, he said, but primarily a function of the material used. “The quality of the earth is the difference between a good adobe and a bad adobe,” he said.

That’s a lesson Yubeta learned during a U.S. Forest Service reconstruction project at Kentucky Camp in the Patagonia Mountains.

He was brought in as the “adobe expert.” Every brick he made on site cracked, he said. The native soil had too much silt and not enough clay.

That would have happened with the bricks used to rebuild a wall at the Canoa Ranch site, said Simon Herbert of Pima County’s Cultural Resources and Historic Preservation Office.

They were made on-site, but the soil was imported from elsewhere.

Breathing barriers

The workshop is part skills-training and part “Chemistry 101,” Jeffrey said, from the composition of the soil and amendments used to make adobe blocks to the formulas for creating lime plaster that will allow adobe walls to shed rainwater, but still breathe enough to release any moisture that does seep in.

Yubeta translated for Luis Fernando Guerrero Baca, of Universidad Autó noma Metropolitana of Xochimilco, as he mixed exact proportions of sand and lime with alum, lye soap or prickly-pear sap to create that breathing plaster.

The real challenge to preserving adobe buildings, Yubeta said, is the continual maintenance they require. “Adobe is a noble material,” he said, but, unprotected, it tends to crumble back into the earth.

That creates interesting questions for preservationists, who must decide whether to simply arrest that decline or restore buildings. The former option was taken at Tumacácori National Historical Park, where the remains of the mission are being maintained and not restored, said Yubeta. When repeat visitors would tell him “you haven’t done anything here,” he would take it as a compliment.

At Canoa, Pima County has chosen to restore many of the buildings at what is now named the Historic Hacienda de la Canoa and Raúl M. Grijalva Canoa Ranch Conservation Park.

The ranch buildings are being restored or maintained at their period of cultural significance — the “ranching heyday” of the 1940s and 1950s when it was known as the Manning Ranch and was the boyhood home of Rep. Raúl Grijalva, D-Ariz., whose father worked there as a ranch hand.

The 4,800-acre site has deeper historical significance, said Linda Mayro, Pima County cultural resources manager. Part of a Spanish land grant, it had been a working ranch since about 1820.

It is in the historical floodplain of the Santa Cruz River and was a reliable source of water for Spanish missionaries and soldiers. It was first called “Canoa” in reports of the DeAnza expedition in 1774, which noted the hollowed out cottonwood logs, or “canoas,” used for water catchment by the Pima natives.

Above the eastern riverbank, archaeologists have uncovered evidence of much earlier habitation.

Building on history

Even though the adobe wall workshop participants repaired Thursday is not, itself, all that historic or significant, it is part of something much larger.

“This is the embodiment of Arizona ranching history,” historian Jeffery said.

“It is the boyhood home of a famous congressman. It represents layers of civilization from the Archaic Period all the way up to the 1950s, as well as the cultural landscape that’s here.”

With care, adobe buildings can last indefinitely, said Jeffery. He worked several years for UNESCO in Yemen, where some mud buildings date to the time of Christ.

You can’t save them all, he said, nor should you.

“Earthen architecture is so vulnerable to the elements that it is always in peril. When we have large, significant structures made out of earthen materials, those are the ones we want to preserve.”