BOISE, Idaho —
This story originally appeared in the Idaho Press.
It’s a building technique so ancient and so durable that it can be found on some parts of the Great Wall of China. And now, a Boise man is using it to construct a home.
Retired smokejumper and self-taught homebuilder Todd Jinkins is currently building his first rammed earth home. It’s also the fourth home he’s built in the past 22 years.
From what he can tell, the rammed earth structure will be the first one in the city of Boise.
“Since the city wasn’t familiar with rammed earth, because this is the first one, it took me a while to get all the permits and get the engineering done,” Jinkins said.
While the city wasn’t able to confirm if Jinkins’ home is the first rammed earth structure because it doesn’t keep track of construction materials, Lindsay Moser, a spokeswoman for Boise Planning and Development Services, confirmed that it is a rare method of building.
Rammed earth walls are constructed by ramming a mixture of gravel, sand, silt and a small amount of clay into place between flat panels called formwork. A small amount of cement — typically 5–10% — is added to the mix to make the walls more stabilized by increasing the rammed earth’s strength and durability, according to Your Home, the Australian government’s guide to environmentally sustainable homes. Often, people will add certain dyes to their mix to give the walls different colors. The result is a unique appearance featuring layered ribboning.
Historically, rammed earth walls are made with the materials found at the site, but Jinkins had to source his building materials from Ruschman Sand & Gravel due to today’s building codes and standards. Jinkins’ mix is made up of 70% sand, 22% small gravel chip rock and 8% Portland cement to be used as a stabilizer. He also has rebar running throughout the walls.
Jinkins currently lives in a more traditional-style home that he also built. When he was smokejumping, he used to get laid off in the winters because there weren’t any wildfires, so he took up building in his spare time and has enjoyed the learning process. His first home took him four winters to build. Jinkins said two things drew him to trying rammed earth this time around: its longevity and energy efficiency.
“I really liked that concept of a house that would last for centuries,” Jinkins said.
Because of the home’s durability, Jinkins sees it as a more sustainable alternative to typical frame houses since it lasts longer. The rammed earth walls Jinkins has constructed are also hydrophobic, which adds to their durability.
According to Dr. Jillian Moroney, an assistant professor of urban studies and community development at Boise State University, rammed earth homes have a lot of benefits that are suited to the Treasure Valley’s climate, including energy efficiency.
“The thick walls make them very thermally efficient, so less heating and cooling is needed. I think they are well suited to desert environments also because we have less rainfall that could potentially damage the structure,” Moroney said.
But Boise also gets cold in the winter, so Jinkins has added insulation to the walls to help with that. Jinkins said once the structure has been heated by his radiant heat flooring or cooled by his central air conditioning, it should be able to hold that temperature for hours or sometimes even days at a time.
While he knows rammed earth homes aren’t for everyone, Jinkins wants people who are interested to not be deterred by difficulties in finding someone to do it or by the potentially large upfront cost.
“I think what people discount is the idea of the longevity of them,” Jinkins said. “If you have a wall or a house that you never have to do any maintenance on, you never have to repaint it, you never have to re-side it or fix the drywall. They don’t really consider that.”
Jinkins started on his structure in April and had help from his neighbor’s son, Ethan Lester, throughout the summer. He anticipates that the house, which will measure about 1,500 square feet, will be completed by next spring.
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