The next battle over market-rate housing in the Mission District took shape Thursday morning as activists met on the corner of South Van Ness Avenue and 26th Street to denounce a five-story housing project they have dubbed the “Titanic Mess on South Van Ness.”

Opponents demanded that its developer — Lennar Multifamily Communities, a subsidiary of the development giant Lennar Corporation — gift the land to the city for fully affordable housing. They also called on the city to delay its consideration of the project.

“Today we’re calling on Lennar to gift this site to the city for 100 percent affordable housing,” said Erick Arguello, a member of the merchants association Calle 24 and a principal opponent of the project.

Arguello said the market-rate building would fuel gentrification and displacement in the neighborhood. He pointed specifically to higher rents for commercial Mission businesses, saying a new clientele would bring upscale shops to a historically lower-income, culturally Latino district.

“When you get more luxury housing, you get people with a lot more money moving into the neighborhood, which creates a different demand for products,” he said.

The project at 1515 South Van Ness Ave. would bring 138 market-rate units and 19 below-market-rate units — fulfilling the city requirement that 12 percent of units on the site be affordable — to the Mission District, as well as six ground-floor retail shops.

The complex would raze and replace the McMillan Electrical building and abut a planned 96-unit fully affordable senior complex to be built by the Mission Economic Development Agency — a point of contention at a February community meeting where audience members wanted a merger of the two sites.

On Thursday, some 25 people gathered at the project site and vowed to fight the project to its death. Roberto Hernandez, founder of Our Mission No Eviction, said the project was out of place in the Mission District.

“It’s a titanic luxury development for the rich people,” he said through a bullhorn.

The Lennar project sits in the Latino Cultural District, a rectangle stretching from Mission Street to Potrero Avenue and Cesar Chavez Street to 22nd Street that the city recognized in May 2014 as a “Latino cultural and commercial district” in San Francisco.

The project “doesn’t fit the vision” of the Latino Cultural District, Arguello said. He said barring an outright donation by Lennar, the city should pony up for the land so it could develop fully affordable housing on-site.

He pointed to the city’s purchase of 490 South Van Ness Ave. — a site slated for market-rate housing that will now become affordable housing — for $18.5 million as evidence that the city could negotiate for the land.

“High-end developments like Lennar do not meet the needs of the Latino Cultural District,” he said. “Lennar does not belong.”

Annabelle Bolanos, who lives near the project site, said a market-rate project on the block would displace those currently in the area, like day laborers who spend time on the corner and “houseless folks around here.”

“If we allow the Titanic Mess on South Van Ness, the floodgates will have opened and it’ll be hard to stop it,” she said.

For its part, Lennar responded to the gentrification charge. A spokesperson wrote in an email that “a full spectrum of housing options” is needed in the Mission District “to prevent rising rents and continued displacement.”

“We believe that building a wall around the Mission is the wrong approach to preventing displacement and gentrification,” the spokesperson wrote.

He also said the firm had no comment on whether it would sell the land to the city, but that it is planning on proceeding with a “well-thought-out development.”

The “Titanic Mess on South Van Ness” is the latest of several monikers for market-rate housing in the neighborhood. The first project to be nicknamed by opponents — the 331-unit “Monster in the Mission” development at 16th and Mission streets — was delayed by a lawsuit last summer and has seen little movement since. The 328-unit “Beast on Bryant” has faced renewed opposition despite a change to the project by its developer that would result in more affordable housing on-site.

Another planned development at 2750 19th St. — across from the Bryant Street development — has been dubbed the “Baby Beast” and would replace a furniture shop with a six-story, 60-unit market-rate housing complex.

That joins the “Fright on Folsom” — a planned 117-unit project at Folsom and 23rd streets — on a slate of several dozen projects to be opposed by Mission District activists in upcoming months.

Not all market-rate developments are on opponents’ chopping blocks, however. For the Bryant Street development, activists who have been opposed from the get-go are pushing for higher levels of affordability on-site but many say they would settle for less than 100 percent affordable.

That is not the case for the project on 16th and Mission streets or the Lennar project on South Van Ness Avenue. Because the former sits next to a BART station and the latter is in the cultural district, Arguello and Hernandez are adamant that those two sites become fully affordable housing or no housing at all.

“Just like the Monster, all the little actions [help] delay, delay, delay,” Hernandez said. “That’s why we’re here today, because we’re going to delay, delay, delay until we kill it.”

Delayed it they have. The Lennar project is scheduled to go before the Planning Commission next Thursday, April 21, but will likely be delayed to June 16, according to a spokesperson for the Planning Department.

Dozens of emails written in opposition to the project — as well as a phone call by Supervisor David Campos — were behind the delay, according to Arguello.