A pop-up is seen in the 1400 block of Shepherd Street NW in Columbia Heights. (Melina Mara/The Washington Post)

The D.C. Zoning Commission took its first action this week against developers of the city’s growing number of “pop-up” homes, voting to reduce the maximum by-right height of ­single-family rowhouses from 40 to 35 feet in some of the city’s gentrifying neighborhoods, including Capitol Hill, Shaw and Columbia Heights.

But developers of pop-up homes — residences built upward that often soar over their neighbors — did win one key concession from the commission. In a split vote Monday night, the five-member commission decided to allow developers to convert their pop-ups into condominium buildings with up to four units, with one reserved for families that earn no more than 80 percent of the Washington region’s median family income of $109,200.

Originally, the Zoning Commission had considered a proposal that would have barred developers from building three or more units in those neighborhoods, a measure designed to make pop-ups less lucrative for developers.

The commission’s decision is not final. But its vote gives residents and developers who have been anxiously following the pop-up debate an initial look at the likely set of rules that would govern one of the city’s most controversial building practices. Later this spring, the commission will take a second, final vote after a legally required advisory review by the federal National Capital Planning Commission.

In the past year, pop-ups have generated impassioned, marathon public hearings across the city, especially in hot residential neighborhoods where newcomers are moving.

Many residents in those neighborhoods get angry when developers buy an old two-story rowhouse and plop a third story on top, or when they raze the rowhouse and construct a brand new three-story residence. Longtime residents argue that pop-ups clash with the established character of their communities, or simply block their sunlight, their solar panels, or even their chimneys.

But pop-up developers have said that pop-ups are essential to meet the growing demand of people seeking to move into the nation’s capital. They have said that condo units within pop-ups give middle-class families less expensive alternatives to move into pricier, established neighborhoods, where rowhouses can cost $1 million or more.

During Monday night’s meeting, the commission voted 3 to 2 in favor of the lower, by-right 35-foot height cap but also allowed residents or developers to pursue a special exception if they want a 40-foot-tall building.

Robert Miller, one of the commissioners who voted against the measure, suggested that the real problem with the pop-ups is not the 40-foot height but the designs of the buildings.

“We don’t need to change a whole zoning framework,” Miller said. “We may need to add design development standards or a special-exception process.”

Michael Turnbull, another commissioner, quickly countered: “We had a lot of comments from the community. We had a lot of concern from a lot of neighborhoods about the heights of the pop-ups. . . . I think this is a corrective zoning measure.”

Even though the commission voted against by-right 40-foot homes in certain neighborhoods, the group did approve a measure that would allow developers to maintain the 40-foot height for three or more adjoining buildings. Turnbull worried this provision would undermine the new 35-foot height cap and entice developers to buy and develop three adjacent properties at once.

“You’re still going to be limited to three stories, so I don’t see that there’s going to be a huge incentive,” Commissioner Peter May said.

In a 3-to-2 vote, the commission agreed to allow developers to build four units in a building as opposed to two or three units, but some restrictions would apply. Developers will not be allowed to build rear additions that pop back and extend 10 feet past the rear wall of any adjacent rowhouse; and they can’t construct pop-ups that block next-door neighbors’ chimneys or adjacent solar panels.

But Anthony Hood, the commission chairman, made it clear he was not happy with allowing developers to carve rowhouses into four-unit condo buildings as a matter of right. He said he’d favor two, maybe three units, with the fourth allowed by a special exception.

“We’re piling people on top of people,” Hood said. “I hear this argument about housing in the city, but for me it’s an infrastructure issue.”

Miller said he felt compelled to give developers four units as a compromise, since the measure would come with so many restrictions, such as requiring that the fourth unit be sold to a family that earns less than the city’s annual median income.

Hood knew his idea for two or even three by-right condo units was not going to be approved. He shook his head. “I don’t want to go down as the worst zoning commissioner. I honestly don’t,” Hood said. “Is anyone interested in my proposal?

Nobody was.