Though much ink has been spilled on the increasingly-divided nature of San Francisco's Board of Supervisors, two of the Supes who are in frequent opposition came together late Monday, agreeing on legislation that, if approved, would pave the way for as many as 30,000 new residences in San Francisco. That is, if building owners chose to take advantage of it.

In a joint press release, D2 Supe Mark Farrell and D3's Aaron Peskin announced that the often-at-odds duo had merged their battling ordinances on Accessory Dwelling Units — the residences most commonly known as "in-laws" in San Francisco.

According to the release sent by both their offices, "the landmark legislation paves the way for the creation of tens of thousands of new permanently rent-controlled residential units, while protecting neighborhood diversity and small businesses. It gives appropriate consideration to neighborhood noticing and public process, while maximizing the potential for additional density within the existing built envelope of projects."

It was decided at the Board of Supes' Land Use and Transportation Committee meeting Monday, the Chron reports, when Peskin, Farrell, and D8 Supe Scott Wiener amended the dueling measures, following months of quarreling "over how those in-law units should be constructed and what regulations they would fall under."

Peskin had first introduced legislation to allow the construction of new units within existing buildings in March. Farrell introduced a competing proposal in May, and last month submitted a November ballot measure on the issue, spurring Peskin to send "a scathing note to the board, saying that Wiener and Farrell had gone behind his back to craft an alternative proposal," the Chron reports.

But all that is water under the bridge, as Farrell will now be pulling his ballot measure, and the Board will this afternoon vote on the legislation, which would, per the Supes' release, "would allow the unlimited construction of ADUs within buildings that are five units or more and will cap new units at no more than one unit in buildings that are four units or less."

"Each new unit constructed would be allowed to be built or expanded within a building’s existing envelope. All ADUs would be rent-controlled rental properties, except for ADUs built in existing condominium buildings with no prior eviction history, which would also provide for new home ownership opportunities."

The legislation would not allow any new ADUs to become short-term rentals (such as Airbnbs). It also "bans such units altogether in parts of The City zoned for single-family homes," the Ex reports.

Already, some are complaining that the legislation is too restrictive. Speaking with the Ex, Sonja Trauss, founder of the San Francisco Bay Area Renters Federation, says that units should be allowed outside the boundaries of the current structure, for example, in a building's back yard.

“People should be able to build to the buildable envelope,” Trauss said. “It is buildable. I don’t really see any downside at all besides the fact that some neighbors might have to let their eyes pass over a new thing that looks different and unfriendly to them.”

Farrell disagrees, however, saying that “I have three little kids. We need a backyard as well...It is a balancing act, and we need to do something that everybody can live with. We have gotten pretty darn close to that.”

"Our housing crisis continues in San Francisco, and I believe we need to do everything possible at the Board of Supervisors to build more housing at every income level," Farrell says via press release.

“This law will help realize thousands of new permanently rent-controlled units, protect and promote neighborhood character and diversity, and will make a meaningful impact in our City’s housing shortage and crisis.”

The full Board of Supes is expected to pass the legislation today. Following a second vote on July 26, it'll hit Mayor Ed Lee's desk for approval, and will become law 30 days after that. The next question is, will any building owners actually take advantage of it?

According to the Ex, that's unclear. Though Wiener passed legislation legalizing construction of ADUs is his district in 2014 and then-D3 Supe Julie Christensen passed similar legislation in hers shortly thereafter, no new units have been constructed. (This, despite the spiffy booklet Planning made for building owners and contractors!) Will the rest of the city be any different? Perhaps if the application process is streamlined, Peskin says, arguing the Planning Department's current hoops are why ADU construction never moved forward in those areas.

A city outreach program for property owners that provides "technical assistance and reference to possible financial assistance through banks" will also be provided, Peskin says, which might encourage more to build.

"I am focused on ensuring that the City does everything possible to incentivize the use of the affordable housing tools we are creating,” Peskin says via release.

“I want the City to work with property owners to encourage use of this program, so we start reaping the benefits as soon as possible.”