Dirt Bricks

What Are Elon Musk's Dirt Bricks Actually Good For?

Plenty—but probably not the purpose he said.

By David Grossman
YOUTUBE/BORING COMPANY

• Tesla and SpaceX chief Elon Musk made a surprise announcement last week: He was thinking about making bricks.
• The Boring Company, Musk's tunneling project, creates tons of dirt that could be compressed into bricks.
• Musk says the bricks could be used to build public housing in Los Angeles, where it's desperately needed. But architects say there are problems with that plan.

Last week, amid sweeping talk of futuristic electric trains and $1 tunnel trips underneath Los Angeles, Elon Musk took a moment to talk about something a little more old-fashioned: bricks. Specifically, real, honest-to-goodness bricks that could be helpful byproduct created by his tunneling Boring Company.

"These are bricks that are made by compressing the dirt at extremely high pressures, adding a little bit, just a small amount of concrete," Musk explained at an event at Leo Baeck Temple in Los Angeles. "We can actually sell the bricks for like, 10 cents a brick or something like that."

Musk dug deeper on Twitter, suggesting the bricks are more than just a way to turn a profit on the mountains of dirt that the Boring Company will inevitably create. The bricks could also be part of a potential solution to the glaring housing crisis in the city of Los Angeles, where 600,000 people in the county are "severely rent burdened," meaning they spend over half their income on rent, andmMore than 8,000 people who previously had housing in L.A were pushed into homelessness in 2017.

In other words, the LA housing problem sounds like it's begging for a creative answer, and Musk's could be an interesting and even altruistic plan. But according to architects we talked to, the Boring Company (TBC) might be out of its depth if it wants to use the bricks to help solve the current affordable housing crisis.

It's not that the bricks are bad. It's that they're bad for the job.

Building With Dirt

To Lisa Matthiessen, National Director for Sustainable Design with HGA Architects, The Boring Company's bricks sound like "another version of compressed earth."

Compressed stabilized earth blocks (CSEB) can be found all over the globe, especially in South America and the American Southwest, because they carry a set of particular advantages. CSEBs are resistant to fire and insects, are good at blocking out noise, and provide a natural passive cooling system. These features make them an obvious choice for hotter climate, much like that of L.A. (To its credit, The Boring Company's own website admits this is not a new concept.)


The Boring Company’s bricks, as seen in Elon Musk’s informational meeting
YOUTUBE THE BORING COMPANY

Matthiessen says it wouldn't surprise her if The Boring Company has found a way to compress bricks faster and cheaper than anyone else. "[It's about] deep pockets and attitudes towards risk. A government would never do it." And there's another good reason to use earthen blocks, which is that they provide an alternative to concrete, which is a major contributor to global warming and rising air conditioning costs. "Any way we can use less concrete, that’s a good thing."

It's All About Space

But no building is constructed in a vacuum—a good structure takes into account the context of its environment. The Boring Company's bricks might be good for a rural house, but they'd be bad for the urban, low income housing that L.A. desperately needs—so says Los Angeles architect David Hertz, founder of the Studio for Environmental Architecture and veteran of environmentally responsible building design

The problem isn't one of structural integrity, Hertz says, but space. Bricks like the one Musk displayed at Leo Baeck Temple are simply too big to use in mass-produced affordable housing units in an urban area. "Land is at a premium," he says. "Every inch matters."

What's more, bricks like Musks' weigh more than standard building materials, requiring a bigger foundation and greater energy use over the course of construction, all for a finished product that would take up too much room. "If your goal is to create attractive affordable housing, your goal is to create as much interior square footage as possible." Hertz says. "And if your walls are thicker than they absolutely have to be, there are fewer units than there could have been otherwise."

Insulating or wiring up such a unit would also be difficult, and add to the space inefficiency. "You essentially have to put another wall in front of that wall," Hertz says "Not only for running electricity but for insulation." Plus there's the risk of mold if there's nothing to keep moisture from absorbing into the CSEB wall.

All of these issues are space issues, factors that reduce the number of units with no additional value. Sure, the materials might be cheap, but housing materials are only one factor in what makes affordable housing so expensive to build in the first place. It's a confluence of factors that leaves The Boring Company's bricks as a poor prospect for low income urban housing, Hertz says.

The Right Tool for the Right Job

Despite all the aforementioned concerns, Hertz says the Boring Company's bricks could be put to good use. Hertz thinks they would be perfect for rural areas where space isn't an issue and affordable housing is still a need.

This approach could involve headaches of its own, though. Building in areas like California's Central Valley would require making sure the dirt is free of toxins. And unless the Boring Company's brick-making process is particularly cheap or efficient, it will also run into competition from other more local sources of CESBs.

Maybe the most practical use for the blocks is another one that The Boring Company has floated: using them to reinforce the very tunnels its digging. While it wouldn't do anything for the affordable housing crisis as Musk floated on Twitter, it would be better for the environment than using concrete for structural support and/or shipping all the dirt offsite. It's not sexy, but it makes sense.