A proposal to create a new zoning district to promote construction of affordable-housing developments in Palo Alto hit a snag Wednesday night, when a deeply divided Planning and Transportation Commission voted to defer its decision for at least a month.

By a 4-3 vote, with Vice Chair Susan Monk and Commissioners Michael Alcheck and William Riggs dissenting, the commission directed staff to perform more analysis on a range of issues -- including parking demand, height restrictions and areas in which the new district could be applied. All three dissenting commissioners advocated for approving the new district and allowing the council to hash out some of its more troubling aspects.

The commission's decision will delay -- though likely not derail -- the adoption of the new "affordable housing combined district," which would be applicable to commercially-zoned parcels. The overlay would work in tandem with the site's underlying zoning and would relax some of the development standards for housing developments that consist entirely of below-market-rate units. It would only apply to areas with a half-mile of major transit stops or "high-quality transit corridors."

In a tense discussion that stretched for more than three hours, commissioners agreed that they would like to see a strong ordinance that promotes affordable housing. That, however, is where the consensus ended. Chair Ed Lauing and Commissioners Asher Waldfogel, Doria Summa and Przemek Gardias all said they would like more time to evaluate the development standards in the new proposals and conduct outreach to developers and the broader community.

Waldfogel suggested that the city identify the range of income levels that the new ordinance should focus on. He argued that it's important for the city to craft an ordinance that would "actually produce units."

"Last thing I want to do is proceed with something that doesn't accomplish the goals," he said.

Summa had a list of specific problems with the ordinance, even as she lauded its broad goal of encouraging affordable housing. The new zone, she said, should ensure that the new affordable-housing developments have heights that are compatible with adjacent low-density residential districts. This would apply to various sections of El Camino Real that are located near single-family neighborhoods and which, for that reason, have height limits that are typically lower than the citywide 50-foot threshold.

She also suggested that the proposed parking requirements -- 0.5 spaces per unit -- may be too low and requested more analysis.

"I don't think we can go forward with an overlay zone that puts such a negative impact burden on its neighbors," Summa said.

The requests for more analysis drew a sharp rebuke from the three commissioners, who saw their bid to approve the ordinance fall by a 3-4 vote. Monk said she is "extremely disappointed" in her colleagues' decision to defer a decision and "embarrassed" about how far the city is behind in providing housing.

"By us not passing it today, we will just delay what is so important to our community and stunt our own goals that we set forth," Monk said.

Alcheck went even further. He accused his colleagues of using "delay tactics" and argued that the real issue in the debate is the "complete NIMBYism" of those who oppose housing proposals.

He described a typical participant in the planning process as a "well-to-do homeowner, strongly averse to changes in their surroundings, time-rich, opinionated and articulate." By contrast, the commission rarely hears from low-income renters, young adults who can't afford to move out of their parents' homes and people "lingering on an affordable-housing waiting list."

"This is a tug of war of sorts but one in which one team isn't even grabbing their end of the rope," Alcheck said.

William Riggs characterized overlay districts as a standard tool for city planners and called the proposed ordinance a "pragmatic policy." He also advocated for immediately approving it and passing it on to the council.

For the commissioners, the Wednesday discussion was the second in two weeks in which they were asked to weigh the benefits of increasing housing against the potentially unpredictable impacts of granting zoning concessions. On Jan. 31, the commission decided that the former justifies the latter when it agreed create a new zoning district to allow "workforce housing" targeting people making between 120 and 150 percent of the area median income.

The commission also decided that the workforce district should specifically apply to a site at 2755 El Camino Real, where the developer Windy Hill Property Ventures proposed a 60-unit apartment building with an aggressive transportation-demand-program aimed at reducing the need for cars.

While the "workforce" district aims to address the "missing middle" (those who make too much to qualify for below-market-rate units but not enough to pay Palo Alto rents), the affordable-housing district would target less affluent populations. It would accommodate individuals with income levels ranging between "extreme low" and "moderate" incomes, as measured by area median income. To qualify for a studio in the "extremely low" category, a person would have to make no more than $25,100; the "moderate" category would apply to incomes of up to $95,150.

The affordable-housing district was also inspired by a specific proposal, though in this case the relationship isn't as direct. The nonprofit Palo Alto Housing, which has not proposed any major projects since its proposed housing development on Maybell Avenue was overturned in a 2013 referendum, is now making a bid to build 61 units at 3709 El Camino Real, near Wilton Court. If the new "affordable housing" district is applied to the site, it would give Palo Alto Housing the parking and density concessions that the nonprofit has requested to make the project financially viable, according to the nonprofit.

To date, however, Palo Alto Housing has not filed its development application. And even if the city adopts the new zoning district, the nonprofit would have to go through the public process of getting its property rezoned and its building approved by the Architectural Review Board.

Danny Ross, senior development manager for Palo Alto Housing, said the proposed ordinance isn't perfect but urged the commission on Wednesday to support it ordinance. Doing so would help address the city's "grave housing crisis."

"Building housing in California is challenging enough. Building affordable housing in Palo Alto is nearly impossible," Ross said.

Not everyone was sold on the new zoning district. Becky Sanders, moderator of the Ventura Neighborhood Association, argued that the proposal is moving too fast that, from the residents' perspective, it "came out of nowhere." She suggested that the proposed relaxation of parking rules will "inevitably lead to cars parked up and down the streets" and create bad feelings between neighbors.

"The surprise ambush on zoning throughout much of the city erodes public trust that the people we elected are working in the interests of the voters who put them there," Sanders wrote.

Others argued that the ordinance doesn't go far enough. Elaine Uang, co-founder of the citizens group Palo Alto Forward, suggested that the city expand the overlay to Stanford Research Park and "General Manufacturing" zones. She also suggested that the city consider allowing even greater density around University and California avenues.

"This Affordable Housing overlay can help us meet our housing needs for the next 10, 15, 20+ years, and we should offer greater flexibility for future affordable housing projects at the mot transit-accessible, service-rich locations," Uang wrote.

The ordinance is one component of a broad Housing Work Plan that aims to roughly triple Palo Alto's housing production. City planners hope to adopt a new zoning ordinance by the end of the year and make further pro-housing revisions in 2019.