This company is building 3-D printed, small homes on existing residential properties to fight back against California's housing shortage. Look inside a unit that was move-in ready in one week.

  • The nation's housing crisis has highlighted the need for faster, cheaper construction, as new construction lags significantly behind demand. 

  • Mighty Buildings, a Khosla-backed construction tech startup, is using a novel material to 3D-print homes quickly. It's begun by focusing on small buildings in backyards that have been made broadly legal across California. 

  • Mighty Buildings cofounder Sam Ruben took Business Insider on a virtual tour of the company's first complete property, a studio in a backyard in San Ramon, California.

While the world of real estate has spent the last half-a-year theorizing about the future of the office, or how in-person retail could survive a pandemic that taught grandparents how to order groceries online, one thing has stayed constant – America has a housing shortage.

A California-based startup, Mighty Buildings, is 3D-printing homes with novel materials to speed up the home building process and help housing supply catch up to demand. They're well-placed to make an impact as the housing shortage is particularly acute in rapidly growing California, which needs an additional 3.5 million homes by 2025, according to a 2016 McKinsey report. The number of houses that are being constructed has already been far below the number needed to meet that goal, and the pandemic has only slowed the progressA 2019 report found that the state needs to build 1.4 million homes just to make up its shortfall in affordable rental units. The pandemic may have shuffled the decks, with San Francisco rents dropping precipitously as some techies look to remote work, but the underlying problem hasn't been solved. The problem is multifaceted and developers, tenant activists, and everyone in between has their own visions for solving the crisis, but new zoning laws and forms of construction have offered at least one path forward. 

Earlier this year, it became legal to build Accessory Dwelling Units (ADU), essentially the legal term for in-law units or small buildings built for residential use on a residential property, in any area that allows residential units. In practice, this makes it now possible to build small units on any residential property in the state and either rent them out or use to house extended family.

Mighty Buildings is using the new ADU law to show off its 3D-printed technology that can print a structure in a day. The Oakland-based startup has raised at least $33 million in total according to forms submitted to the Securities and Exchange Commission, including a $20 million August 2019 Series A led by Silicon Valley-heavyweights Khosla Ventures. 


The company prints its homes with Light Stone, a material that sets into shape when it's hit by UV light, saving the hassle and wait related to building with concrete and other materials that take days to harden. This also makes it possible to 3D-print a roof, something that is impossible with other building materials. The company's plan is to prove its concept with ADUs, while developing the capacity to eventually print larger, multi-story structures. 

"ADUs are just the start, it's a niche market to prove the concept and show viability," Sam Ruben, chief sustainability and partnerships officer and cofounder of Mighty Buildings, told Business Insider. 

The company sells direct to consumers, with the smallest model costing $115,000, but is also exploring partnerships as a way to scale their business. Ruben told Business Insider that partnerships will be crucial to allow the startup to build as many homes as possible, putting a dent into the state's housing deficit.

In September, the company announced a partnership with LA-based developer the Palari Group, building ADUs on sites where Palari is building multifamily properties.