San Francisco's high housing prices may be driving some people into the ground, literally.

Developer Chris Elsey of Elsey Partners in Manhattan, Kansas, has plans to build two apartment buildings in San Francisco's Mission District that would each include two basement-level floors with 88 so-called "sleeping pods," measuring about 50 square feet each, just a little bigger than a king-size bed. (See renderings of the plans in the gallery above.)

Tiny living spaces are increasingly becoming a way to add housing in big cities. But this approach seems more extreme — and has yet to receive approval from the San Francisco Planning Department.

"The contentious part is these below-grade sleeping pods," said Elsey, who started the company with his twin brother and has projects around the country. "When you’re building something, the plans have to be approved by the Planning Department and the Building Department. These below-grade sleeping pods meet the building codes, but there’s this perception from the Planning Department that it’s not something any human being should be exposed to or allowed to do."

San Francisco's Department of Building said in a statement, "“At this point we have not received any permit applications for the project. Until a developer applies for a building permit and submits building plans for DBI review, we are not in a position to say whether the proposed project will comply with San Francisco’s Building Code.”

The plans to transform two surface parking lots that are kitty-corner from each other at 401 S. Van Ness and 1500 15th St. have been in the works for more than four years. Above ground, the building would feature eights floors with 161 units — each 200-square-feet including a bathroom and kitchen.

In the basement-level floors, the sleeping pods are stacked on top of one another, like bunk beds, with one side opening to a common living space. It has a feel similar to a youth hostel or college dorm. A curtain could provide privacy in the sleeping pods, but the city's building code doesn't allow them to be closed in with a wall and door that closes. The basement-level housing units don't have windows that open to the outdoors, but Elsey argued they receive natural light as they circle common living spaces facing an outdoor courtyard in the center of the building.

With close living quarters, the underground spaces would likely have "house rules" that residents would need to obey.

"Obviously people don’t like it when people come home drunk and belligerent," he said. "And no pod sex. I think anyone who has been in college or a dormitory, you’ve had experiences where you prefer that people do those things in private."

The sleeping pods would rent for $1,000 to $1,375 each and the studios for $2,000 to $2,375. Elsey feels that in San Francisco, where the average rent for an apartment hovers around $3,700 (according to Rent Cafe), the lower-cost units will be in high demand.

"We’re trying to build the most affordable market-rate living arrangement," said Elsey. "That’s been our main objective."

He added: "We’re trying to utilize this below-grade space that has traditionally been used for accessory uses such as bike parking. What’s more important, beds or bikes? I guess it’s up to everybody’s opinion, but my opinion is there’s an incredible housing shortage in San Francisco."

Altogether, the project near the 16th Street BART station has the potential of adding nearly 500 bed spaces. Elsey said it could take at least two more years for the plans to get approved and then another 18 months to build.

"We’re in it for the long haul," he said. "There’s a limited amount of land in San Francisco," he said. "By allowing these below-grade units that are 100-percent building-code compliant, you’re making the best use of the land. I can see this living arrangement isn’t for everyone. But we want a diversity of housing stock. Not everyone can afford to pay for their own studio apartment in San Francisco that’s going to run you upward of $3,000."

This story was updated on Jan. 10, 2019, with a statement from the San Francisco Department of Building.

Amy Graff is a digital editor with SFGATE. Email her: agraff@sfgate.com.