The Urban Haunted House in Rockville held casting calls for Zombie actors Saturday at the Rockville Pike location. Heather Riley, 23 Aspen Hill; Gal Gazit 17, Rockville; McKenna Murray, 15, Bethesda; Portia Joo, 30, Bethesda listen to John McCambridge giving directions. (Brian Lewis)

Down the hall, men in workboots carry ladders or tweak wiring, trying to get a zombie-themed haunted house up and running in time for Halloween.

With less than a month before The Warehouse: Project 4.1 opens Sept. 28, Justin Watson, director of hiring and public relations, is busy fielding calls from prospective zombie actors and checking the progress of installing signs outside.

A year ago, Watson and several friends went to a haunted house in Busch Gardens in Virginia. They were impressed by the long lines of people waiting to see the attraction, but not by how scary the haunted house was. Back home, they started talking about building their own attraction in the Rockville area.

“We could do this, and we could do this better,” Watson said.

The group eventually formed Hallow Inc. Watson cut back his hours working in human resources for a wholesale souvenir company to work on the haunted house. Chris Hoover, who owns an Internet marketing company, became director of marketing and creative direction. Joyce Roldan, whose day job is clerking for a judge, became director of operations. John McCambridge and Christian Lowe, who own a construction company, became director of production and director of construction, respectively.

The result was a haunted zombie attraction called The Warehouse: Project 4.1, built in a 37,000-square-foot space on Rockville Pike that used to house a Filene’s Basement department store. Hallow Inc.’s five founders and three silent partners are funding the project.

The story behind the attraction, Watson explained, was inspired by a study the U.S. government conducted on victims of nuclear fallout during the Cold War. Hallow Inc.’s storyline imagines that a private company began conducting experiments on some of the victims.

“In 2012, they brought it to Rockville,” Watson said. “Here, they started doing testing, and something went terribly wrong. ... What it’s doing is creating these mutant or hybrid-type zombies.”

The five friends filled their zombie-infested warehouse with special effects to build suspense and create an experience that they think will be more frightening than the typical haunted house staples. That means fewer animatronics and more live actors — about 50 — to jump out from around corners and rattle chain-link fences. As patrons walk through a series of rooms and hallways that make up the attraction, they will pass an abandoned biohazard warehouse, a trashed hospital and other rooms that make up the zombie facility. Walking through the haunted house takes about 20 minutes.

Watson said one of the things that makes their haunted attraction different from others is that it’s in town — about a block from the White Flint Metro Station — rather than out in the country.

“We wanted something that would allow people that are from the city and normally can’t get out to places like Poolesville and Germantown [to visit],” he said. “... And something to keep people out of trouble during Halloween is always nice. Instead of smashing pumpkins, you can come and hang out here and have a really fun time. We think that this is going to change how haunted houses are in this area.”

The group drew inspiration from zombie and horror movies like “Paranormal Activity,” which had a relatively low budget and relied on building suspense and fear of what might be off screen rather than on big-budget special effects.

Watson said the haunted house also features “faster, more aggressive-type zombies,” like those in the 2004 remake of “Dawn of the Dead.”

Although the attraction’s owners are not entirely sure why zombies have become such a big part of popular culture in recent years, they have caught people’s imaginations in this area and in the nation as a whole.

“People are so worried about the end of the world, and when you think about the end of the world, what’s the coolest way the world would end? Zombies,” McCambridge said.

He said TV shows such as AMC’s “The Walking Dead” have fueled the zombie craze, and now, “everybody wants to be a zombie.” To that end, Hallow Inc. plans to use Facebook to recruit zombie fans to become zombies for a night. The company will fit volunteers out with zombie makeup and put them at the front of the attraction to scare visiting humans.

Watson and McCambridge are most excited about the last room in the haunted house. They’re keeping it a surprise, but they hope it will be the one big thing people will talk about after they leave the attraction.

“Zero people know what it is, but it’s going to be terrifying,” Watson said, grinning.

In the event of a real zombie apocalypse, Watson advises working together with other survivors and stocking up on water, canned goods and Twinkies, which play a role in the comedy-horror film “Zombieland.” Physical fitness also helps.

“I’m a runner, so I think I have a pretty decent chance when it comes to running,” he said.

McCambridge is less optimistic.

“I’m toast,” he said.