Kyle Retzik and his family adore their home in Bernal Heights, where friends and familiar faces live around them. But after a “faceless” new property company swooped in a few months ago and nearly doubled their rent, Retzik said he needs to move.

This family fell victim to a loophole in San Francisco’s eviction-control laws: Landlords and building owners can circumvent eviction protections on single-family homes and rented condominiums by jacking the rent up far above market rate, with the intent of making the residence unaffordable for the tenants. District Nine Supervisor Hillary Ronen plans to introduce legislation Tuesday aiming to shut that loophole.

Ronen’s ordinance would amend the Administrative Code to specify that an excessive rent increase intended to “defraud, intimidate or coerce the tenant into vacating such a rental unit” would qualify as tenant harassment. Violators would face a $1,000 fine and up to six months in jail. The ordinance, however, wouldn’t have the power to regulate the rent.

“When you’re displaced from a home with a reasonable rent, you often move out of the city,” Ronen said. “It’s really rare they get to stay in the city unless they have an incredibly high-paying job.”

The ordinance would cover single-family homes and condominiums because those units are protected from evictions without just cause, but not from rent increases. Under San Francisco laws, if a landlord goes out of business or wants to move into his or her own property, the landlord must pay tenants a relocation fee — as much as $20,000 to $30,000 in some cases — and give them 60 to 120 days’ notice, or more, depending on the reasons for the eviction.

Tenant attorney Joe Tobener says his law firm takes 50 to 100 cases a year where landlords force a tenant out and avoid paying relocation fees by simply raising the rent far above market rate.

“If the rent increases to market rate, that’s fine,” he said. “But if the rent increase is motivated by an eviction, then that’s where we take issue.”

Ronen’s ordinance would make it unlawful to impose a rent increase in “bad faith.” Signs that an increase was imposed maliciously, she said, include jacking up the rent above market rate and modifying a unit to remove it from rent control protections.

In a 2015 case in Bernal Heights, Deb Follingstad’s landlord modified her two-unit home into a single-family unit. That allowed her landlord to legally increase Follingstad’s rent from $2,145 to $8,900, as the unit was no longer subject to rent control. In other cases, landlords have done things such as removing a kitchen and a bathroom within a two-unit home to turn it into a single-family home.

Follingstad’s case caught wide attention in the Bay Area as an illustration of the out-of-control housing market. Follingstad, who moved out of the home after the rent increase, filed a wrongful eviction suit against her former landlord and won a $400,000 settlement two years later.

Tobener said he would often win wrongful eviction cases like Follingstad’s, but the San Francisco Superior Court has “reversed course” and suddenly stopped allowing such cases to go forward. Because of the uncertainty, Tobener said Ronen’s legislation is particularly important.

While Tobener said Follingstad’s case is representative of many cases he sees, he said Retzik’s is more unusual.

Retzik said the owner of his house went into default, and the property was bought in 2017 by a real estate company, Breckenridge Property Fund, at an auction. Shortly after, he was served with an eviction lawsuit. The lawsuit was dropped a few months later — but his rent was jacked up from $2,400 to $4,000 a month.

An agent for the company could not be reached for comment Tuesday.

Retzik, who works at Yelp, said he is able to pay his rent for now — but the increase is quickly eating into his family’s savings. He said he will start looking for another home, a daunting task in such a tight housing market.

“I love it here. We have loads of friends in the neighborhood, and it’s killing me that I have to leave,” Retzik, 43, said. “If there’s a loophole by simply raising people’s rents, then what is the point of having the law? There needs to be some sort of teeth so that people don’t essentially break the law.”

Ronen said she believes her “straightforward” legislation will be well received by the Board of Supervisors.

“It’s not as frequent as a problem, but when you displace 50 families a year, that’s a big deal in San Francisco where we have the lowest number of children of any major city and an affordability crisis,” she said.

Trisha Thadani is a San Francisco Chronicle staff writer. Email: tthadani@sfchronicle.com Twitter: @TrishaThadani