Cottage industry: The ups and downs of building backyard homes in SF

The simplest solution to San Francisco's housing crisis, development advocates say, is to build more housing units and more buildings to house those units.

But in a city with strict height controls, little undeveloped land and nowhere to expand, that solution — and Mayor Ed Lee's goal of getting 30,000 new housing units on the market by 2020 — begs a simple and often stumping question: Where?

For an answer, a growing number of city officials and housing activists are looking at backyards.

Yards and other private open spaces are increasingly being seen as places where badly needed housing could easily be built without affecting prized neighborhood character. The potential is huge: With almost 121,000 single-family homes and another 81,590 lots with buildings housing between two and four flats in The City, there could be room for over 100,000 or more “backyard cottages,” as the San Francisco Public Press posited last summer.

But replacing a neglected backyard with a badly needed home is not as simple as it sounds.

In vast swaths of The City's westside, where 25 percent of developed lots must be open space by law, it's illegal to build anything larger than a 10-by-10-foot shed.

And in Corona Heights, where lots allow for multiple buildings, one developer's quest to build second homes on adjacent lots has taken years, with staunch resistance from neighbors at every step.


In summer 2013, two adjoining lots on Ord Court, a dead-end street tucked into the steep and winding roads near Twin Peaks, were sold to Kenneth Tam, according to property records.

Each lot contains a single-family home, one built in the 1950s and the other in 1910, with a total appraised value of $2.4 million, according to the Assessor-Recorder's Office.

Soon after the sale to Tam, plans were filed to add large second homes to each lot. One would be four stories and the other three, with the entrances on States Street up a steep hill from the existing homes' front doors on Ord Court.

In both instances, 25 percent of the lots would remain undeveloped backyard, which is the minimum amount allowed in the area. And in both instances, Planning Department staffers recommended approval. However, complaints from neighbors, who are concerned about the removal of backyard trees where one of the homes would go, have stalled the project.

Other home-expansion projects in the vicinity have caused considerable outcry — and in one instance, a potential health hazard when a home under dramatic expansion and owned by Port of San Francisco Commissioner Mel Murphy collapsed and slid down a hillside in 2013.

Since then, Supervisor Scott Wiener has proposed a tougher approval process for projects that would cover more than 55 percent of a lot or add a home of 3,000 square feet or more.

The proposal would only cover a select area in Corona Heights, and would apply to “monster homes” rather than bona fide “cottages,” said Wiener, but the outcry from neighbors and accompanying action from the local lawmaker may be a cautionary tale.

As for whether or not a second building could be appropriate on some lots in Corona Heights, “it's a case-by-case basis,” Wiener said, declining to comment on an individual project.


Navigating the planning code and other regulations to legally build a second home is difficult.

In many areas, lots have a required rear yard that can't be built on at all. A specific minimum distance is also required between the main home and second.

And fire-safety regulations may require the second home to have a direct exit to the street that does not go through the main building.

For these reasons, “a number of people have done it, but the feedback has been, 'It was extremely expensive and time-consuming and I wouldn't recommend it,'” architect Mark Hogan said.

Hogan's firm Open Scope Studio has been hired by the Planning Department to craft a handbook for adding second dwelling units in existing buildings, an alternative to building a second home. It's a much simpler process, and in some cases does not require notifying neighbors.

“For most property owners, adding another unit to an existing building is much more practical,” he said.


City leaders have recently put forth proposals to make it easier to add extra housing to properties.

For instance, up to 50,000 in-law units that are often stashed in garages, underneath stairs or in former storage spaces could become legal, recognized housing under legislation passed by the Board of Supervisors last year and legislation authored by Wiener and passed at the board Tuesday. Wiener's law would allow the addition of in-law units to buildings undergoing seismic retrofits.

Also Tuesday, Supervisor Katy Tang, who represents the Sunset, asked the City Attorney's Office to craft a law to legalize backyard cottages in areas zoned for single-family homes.

That could mean cottages would be allowed in much of the Sunset and Richmond, along with Ingleside, Excelsior, Visitacion Valley and Bayview-Hunters Point.

The Sunset has “many homes that have large backyards that could accommodate” additional dwelling units, Tang said.

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