They’re like skyscrapers in small villages: renovated townhouses — but between 40 and 65 feet high — right next to squat, two-story rowhouses in Washington neighborhoods from Petworth to NoMa to Adams Morgan.

Their common nickname: pop-ups. Their common epithet among neighbors and on local blogs: monsters. Middle Fingers.

These skyward-extending residences are spreading across the city, fueled by small developers eager to cash in on the District’s real estate boom and seize any inch of available real estate, which these days means vertical empty space. Though developers have the right to build upward — and say they are providing needed housing stock — the city is evaluating how it can ensure that pop-ups in some neighborhoods reflect their community’s character.

Cities from Philadelphia to New York to Amsterdam have seen the proliferation of pop-ups. But Washington, which began seeing the first wave about 10 years ago, is now experiencing a rush. What began largely in Adams Morgan has now come to streets all over the city, from 17th Street NW to Sixth Street NW to K Street NE to Kenyon Street NW.

Anyone can drive around the District and find them. The five-story building at 1013 V St. NW dubbed “the Monster” is the most notorious. But the pop-up bible is the PoPville blog, which for several years has chronicled the advance of pop-ups with the same curiosity people had when McMansions began cropping up on old farms in Northern Virginia. (The “PoP” in the blog’s name stands for Prince of Petworth, the Web site’s original name.) Dan Silverman, the site’s publisher, frequently posts his and readers’ comments, along with photographs of some of the more unusual buildings.

Real estate agent Natalie Middleton does a walk through of a home up for sale in Northeast Washington on June 12. The residence had undergone a renovation, which included adding an additional level to the home. (Amanda Voisard/For the Washington Post)

“Dear PoPville — Any way to stop a pop-up?” read one headline in December. A reader sought Silverman’s expertise, saying, “My block in Shaw has fortunately been spared from all the popups . . . until now. . . . Since it has literally just started, is there a way that I can check or even oppose its permits?”

The post received dozens of comments.

“Get employed [by the] DCRA,” wrote the first of more than 100 commenters to the blog post, referring to the D.C. Department of Consumer and Regulatory Affairs, which enforces zoning rules.

Pop-ups are emerging in parts of the city zoned commercial and residential. In a process analogous to tear-downs in the suburbs, older rowhouses are scooped up by developers with a ready supply of cash. The homes, often dilapidated, are torn down and rebuilt, or remodeled and extended, to the maximum heights allowed by zoning regulations — heights that in the past never needed to be reached because space wasn’t at such a premium.

Now, Washington, teeming with new restaurants and gigantic condo buildings in once-impoverished neighborhoods, has so much more housing demand than supply that, as of May, the average condo or single-family home was selling in about 45 days.

“That’s well below what it should be. It should be six months — that’s what the industry tells us is a stable market for both the buyer and seller,” said Thomas Daley, a board director of the Greater Capital Area Association of Realtors, which released the data recently . “Because the rate’s at about 1.5 months, the advantage goes to the seller. Things are going within days. A lot of times, it doesn’t even get to the open house.”

The tight inventory is pushing prices up. Last month, the median price for a home in the city was about $530,000, an 8 percent increase from the previous May, according to data released by RealEstate Business Intelligence, a subsidiary of MRIS, the Rockville-based multiple listing service.

A developer purchased a two-story row house at 1013 V St. NW and added 3 stories. (Sarah L. Voisin/The Washington Post)

Pop-ups allow builders to tack on new units without having to purchase large blocks of real estate and invest in an enormous, dormitory-style building. Pop-ups also enable incoming residents to squeeze into hot neighborhoods and condo buildings with much smaller fees than those in pricey places such as 14th Street NW.

In the case of the Ava, the so-called “Monster” on V Street NW, the building is in a commercial zone that allows residences to be as high as 65 feet. The five-story aluminum-and-steel structure — topped with a huge eye-shaped window that one Prince of Petworth reader thought was like the evil “Eye of Sauron” from the “Lord of the Rings” — towers over its neighbors.

Despite the building’s modern look and amenities, the middle unit, listed for about $749,000, and the penthouse, listed for about $800,000, have not been sold. Nate Guggenheim, a real estate agent for the Ava, said the bottom unit, listed for about $400,000, is under contract.

“I think the economics are such that it makes sense to do these projects,” Guggenheim said, adding that he’s had “dozens” of potential buyers look at the penthouse suite. “We’ve had people question the design of this, but it would make sense to build a bunch of them and combine several.”

The ownership of some pop-ups is difficult to learn. Guggenheim declined to reveal the individual behind the limited liability company that owns the Ava. Secrecy also hovers over another highly visible pop-up, a five-story building at 1839 Sixth St. NW, next to Shaw’s Tavern. The building is expected to offload its seven units this fall.

According to public records, a District-based entity called the Ella LLC owns the property, but Capital Bank, which is financing the project, and Michael Weisskopf, a former Washington Post staff writer who is the building’s broker, declined to name the owner.

The structure, which replaced an old rowhouse and a vacant lot, is in a commercial zone that permits buildings to be as high as 50 feet. The next-door neighbors don’t mind it. “Maybe I don’t like the black siding,” said John Douglas, who lives in the adjacent rowhouse he bought in 1992. “But it’s the developer’s right to do it and, whether it harmonizes with the community, people will get used to it. There has to be a balance where people have the right to make money.”

Douglas, a retired developer, said he might one day want to have his house turned into a pop-up.

Another neighbor, Laura Gramling, a consultant, feels the new pop-up will make the neighborhood safer. “I am not opposed to pop-ups in principle. It just depends on what they look like. This one is not glaring,” she said. “It’s an improvement over what had been a blighted property.”

But in neighborhoods such as Adams Morgan, pops-up prompt a bit more controversy. D.C. Council member Jim Graham (D-Ward 1), who has criticized pop-ups to fellow council members, said the buildings are geared toward the well-to-do and don’t provide what the District really needs: affordable housing in trendy areas.

“Supporters of pop-ups — other­wise intelligent people — talk about the need for Washington to respond to the great housing demand. That’s patently absurd,” Graham said. “This is about profit. It’s about the historic streetscape in the city. And it’s about, when will it end?”

The D.C. Office of Planning was expected on Friday to publicly release proposals on pop-ups, said Jennifer Steingasser, the office’s deputy director. Her office has been examining whether the current 40-foot maximum height is “appropriate” for some neighborhoods in residential zones.

The Zoning Commission will review the proposal. It would have to approve any new regulations on pop-ups, but a vote isn’t expected to happen for several months.

Steve Callcott, the Planning Office’s deputy preservation officer, said he and his colleagues also might propose the creation of “conservation districts,” a status for which neighborhoods could apply that would force pop-ups to come under city review before getting approval.

Over on K Street NE, Micheal Watson, owner of Taja Investments, believes the phrase “pop-up” is a derogatory label for the three-story building he plans to put on the market late this month or in early July. The bottom unit at 507 K St. NE, with three bedrooms and 3 1 / 2 baths, will be listed for $840,000. The penthouse, with the same number of bedrooms and bathrooms but with rooftop access, will go on sale for $1.2 million.

Watson likes pops-ups so much that he built another one four blocks away on the same street.

Rodney Pais, a retired Army pilot who lives next to the pop-up at 507 K St. NE, calls the new tall building “gaudy” and an “oddball.”

But Watson shrugs off the name-calling.

He said he bought the building last year for more than $400,000 and put almost half that amount into renovations, so selling it as a two-story home — for about $800,000 — wouldn’t have been worth it. To make any money, Watson had to make the building taller and divide it into two units, he said.

But labeling his building a pop-up? He prefers a more nuanced description.

“To me, it’s a simple rowhouse with an extension,” Watson said. “Pop-up? I put too much thought and work into my homes to call it a pop-up.”

Jennifer Jenkins contributed to this report.