Sean Kieghran, president of San Francisco's Residential Builders Association, said he supports getting rid of single-family only zoning but doesn't think it will result in many new units. Kieghran said that building fourplexes requires either two staircases or a staircase and an elevator, which takes up too much of the site.
And, unless the city streamlined the process of building a fourplex on a single-family lot, builders would run into too many bureaucratic obstacles, Kieghran said. "With how long it takes to get through planning and fire and DPW and all the other red tape it's not likely we are going to see anybody building fourplexes anytime soon," he said.
...
One of the few architects to design fourplexes on single-family sized lots in the last few decades is Daniel Solomon, who has worked on three such projects...
"These are nifty little projects, but they won't make a big dent in the housing need," Solomon said. "That zoning is a tool to create housing production is a widely held and completely fallacious idea. Just because something is permitted doesn't mean it happens. It's very hard to find a vacant lot or tear down at a price that would work."
He said the fourplexes he designed and built were profitable, but barely. And they took as much time to design and execute as the 100-unit complexes his firm, Mithun, is known for.
"You would need to find a developer willing to take a risk on a minuscule profit and an architect who enjoys brain damage," he said. "They are complicated little projects. It's the absolute opposite of economy of scale."