Author(s): Jesse Roman. Published on March 1, 2019.

Racked and Stacked

The growing popularity of rack-style facilities for car storage presents an emerging set of fire concerns for safety experts


PARKING STRUCTURES ARE RAPIDLY evolving in ways that allow them to squeeze many more vehicles into much less space in order to maximize costs and efficiency.

A garage set to open this year in Houston, for instance, boasts 244 parking spaces squeezed into a building with a footprint of just 700 square feet—according to simple math, that’s one parking spot per 2.8 square feet. By contrast, before being destroyed by fire last year, Liverpool’s eight-story King’s Dock car park—a traditional concrete parking facility built in 2007—could accommodate 1,600 vehicles within its 53,000-square-foot footprint, or one parking spot per 33 square feet.

The Houston garage, designed by a company called U-tron, achieves its remarkable feat of efficiency by utilizing robots to stack vehicles on mechanical racks 10 stories high. U-tron’s robot attendants can park vehicles 4 inches apart, with 6 inches of overhead clearance, according to a recent article on Currently, the company has eight automated garages in operation, most in high-end residential buildings in New York and New Jersey, with 25 more under development in the United States alone.

U-tron is hardly the only company building these new-era garages—across the US and around the world, stackable garage configurations are spreading quickly as mechanization and automation become more advanced and more affordable, and as city developers look for parking solutions in areas where land is as valued as gold.

While the spatial benefits of these new garages are clear, many researchers and code developers are worried about what such tightly packed vehicle arrangements may mean for fire protection. Currently, there is little guidance in NFPA 13, Standard for the Installation of Sprinkler Systems, or NFPA 88A, Standard for Parking Structures, addressing these new parking configurations. That’s because little research has been conducted to figure out how fires might burn and spread in such densely packed garages and what kind of sprinkler design and density are sufficient to put fires out.

The NFPA 13 technical committee has received questions about these types of facilities and is aware of the standard’s silence on the issue, said Wes Baker, a committee member and researcher at FM Global. He and others on the NFPA 13 committee have asked the Fire Protection Research Foundation to undertake a project to answer some of the lingering questions to enable them to reliably offer system designers guidance. It’s still too soon to say if the Foundation’s planned project on parking garage vehicle fires this year will include research on these new types of garage configurations.

“We’ve seen car storage racks that are as high as the building, which is a totally different animal than what NFPA guidelines on traditional parking garages were set up for,” Baker said. “Heat likes to travel vertically, but instead of flaming up and hitting concrete, the cars sitting above it could be exposed to flames. Instead of a two-dimensional fire, you have a three-dimensional fire. This to me is a storage type of arrangement, and you’d have to protect it like a warehouse facility that is storing cars.”

Baker believes that only installing overhead sprinklers on the ceiling would be ineffective in these stack arrangements because cars above would block water from getting to cars below. He imagines an in-rack sprinkler arrangement, where sprinklers are located on each level of the vehicle stack, would likely be necessary. “But the problem with that is these cars are constantly moving in and out and so you have to be careful with all moving parts that you don’t end up knocking off a sprinkler,” he said. “You’ve got to make sure it’s practical as well as functional.”

On top of those logistical questions, dozens of other variables would make any comprehensive guidance for sprinklers in these new garages tough, said Steven Wolin, an NFPA 13 technical committee member and vice president at Reliable Automatic Sprinkler Co. “There are so many vehicle storage configurations that could exist for any particular garage, which is one of the biggest challenges,” he said. Variables such as the distance between vehicles, how many are stacked on top of one another, and how ventilated or enclosed the space is can make big differences in how a fire burns and spreads, and what sprinkler protection is needed.

Regardless, construction on these facilities continues across the world. “For now, it is still one of those challenging scenarios where the buildings are being built and somebody has to figure out how to put a protection system in,” Wolin said. “You just have to err on the side of being extra conservative in the design, knowing there isn’t a whole lot of guidance out there right now.”

JESSE ROMAN is associate editor for NFPA Journal. Top Photograph: Getty Images