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Earth Notes: Turning Mud into Wildfire-Resistant Homes

Scientists test strength of mud blocks against high heat
Karin Higgins/UC Davis
Michele Barbato’s lab is investigating earth block construction for wildfire-resilient housing. He’s also tested the blocks against earthquakes, hurricanes and tornadoes, with promising results. PhD candidate Nitin Kumar burns wood and a fire resistant brick demonstration at Bainer Hall on June 11, 2021.

Researchers at the University of California-Davis want to learn how to build fireproof houses. It’s an urgent task for a new problem: increasingly fierce wildfires driven by climate change. But the technology that could hold the answer is an old one: earth blocks made from mud and water.

People have built houses out of earth for at least 10,000 years. Many of those structures have stood the test of time, from the Great Wall of China to the cliff dwellings at Mesa Verde. Tests show the material is capable of withstanding hurricanes, tornados, and earthquakes. But what about wildfires?

Scientists at the Climate Adaptation Research Center made earth blocks out of soil gathered from the town of Paradise, which burned in the disastrous Camp Fire of 2018. They added water and a little cement, and tested the blocks in a furnace at temperatures as high as 1,000 degrees Celsius. Early results suggest the material can not only resist fire, but actually becomes stronger when it’s burned. The blocks also don’t release toxic pollution when exposed to fire, saving lives in more than one way.

Building earthen homes is nearly a lost art in the United States. Few contractors know how to work with the material, and building codes are designed for wood, steel, and concrete structures. It will take widespread changes to the political and economic systems that govern homebuilding to make earthen construction the norm. Yet this ancient technology has the potential to transform locally sourced soil into inexpensive, sustainable homes—homes that will still be standing after a wildfire.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.