By Ellen Gerst
Chattanooga Times Free Press
CHATTANOOGA, Tenn. — Chattanooga will allow multifamily buildings to be built with just one staircase, rather than two.
Council members voted Tuesday to take advantage of a state law passed last year that creates an exception to the International Building Code.
Council chair Jenny Hill of North Chattanooga introduced the measure in June.
We’re looking at opportunities to build more what people would call ‘missing middle’ kind of structures,” she told council members at a June 17 meeting.
The missing middle typically refers to denser, smaller housing units — including smaller apartment buildings or cottage-style houses. They can add density while blending into the character of an existing neighborhood, Hill said.
“In my district, for example, along Forest Avenue, Tremont, Mississippi, there are multiple different buildings that are four, five, six units that just go right along with the rest of the single-family neighborhood,” Hill said. “Typically, a single-stair building can fit on a regular urban lot.”
The new single stair ordinance will allow developers to build up to five stories with a single stairway, with a maximum of four units per floor. The state’s maximum allowance is six stories on a single stair.
The city’s ordinance didn’t adopt the state maximum due to safety concerns, Director of Housing Finance Hanneke van Deursen said.
“That came out of conversations with our Land Development Office and Fire Office, and it has to do with what the Fire Department felt comfortable they could rescue people from,” van Deursen said by phone. “The height of the ladders, the size of the trucks.”
The new rules also require sprinklers to be installed in each unit, Hill said, after an ordinance passed recently had loosened sprinkler requirements for smaller multiunit buildings.
Adding sprinklers can cost as much as $30,000 per unit, Hill said.
“So this may not actually increase low-cost building,” she said, “but it will allow us to build smaller-format buildings in the city of Chattanooga and also add one additional unit per floor.”
When a North Shore apartment building had to evacuate in December because of a fire that started in its parking garage, most residents were rescued from windows, not the stairwell, Hill said.
Eliminating the need for a second stairway also enables more windows to be built, potentially allowing more bedrooms in each unit, Hill said.
After the state began allowing those buildings in 2024, cities including Jackson, Nashville, Memphis and Knoxville have adopted single-stair ordinances, local architect Matt Lyle said.
They were once only championed on the fringe of architecture, Lyle said, but have become more common in recent years. Some architects are totally in favor of single-stair housing as an affordability tool, while others oppose it out of safety concerns, he said.
Seattle’s building code has allowed single-stair buildings since the 1970s, Lyle said. The council that oversees the International Building Code (which only applies to the U.S. and Canada ) has indicated it won’t adopt single-stair regulations until enough places adopt them locally, said Lyle, who also sits on Hamilton County’s Planning Commission.
Worldwide, there seems to be no correlation between single-stair buildings and fire danger, he said. Switzerland, which allows single-stair buildings of any height, has the lowest average fire deaths of any country, while the U.S., where they’re highly restricted, is around the middle of the pack, Lyle said.
“The majority of the world is building higher buildings around a single stair than this,” he said by phone.
The stairways in those buildings will have to be pressurized, according to the ordinance, which prevents smoke from a fire inside a unit from rushing into the stairwell, according to the ordinance.
Lyle said he sees the buildings as another tool in Chattanooga’s affordable housing toolbox, like incentives for affordable housing also passed by the council Tuesday.
“I don’t think we’re going to probably see a flood of this project type, similarly to when the accessory dwelling units were added to the zoning ordinance a few years ago,” Lyle said.
In the U.S., where land and lumber were more abundant than in Europe, it was easier and quicker to build wooden structures that were prone to burning, Hill said. The two-stair requirement came as a way to make it easier for residents to escape if a building caught fire.
“We’ve gotten a lot better at building buildings that don’t burn down,” she told council members. “There’s not the volume of concern that there once was, because of a combination of how we build and our firefighting techniques.”
The city rules will also limit how far a unit’s door can be from the stairway — a maximum of 20 feet.
“When people think of single stair they think, ‘Oh, there’s only one way to get out,’ but it does not compromise people’s ability to exit the building,” council member Dennis Clark of Cherokee Woods said at Tuesday’s meeting.
It’s expensive to build stairways, van Deursen said, and developers don’t make money on that part of a building. Only having to build one stairway increases how much of the building is actually being used, she said.
“In a large multifamily building with apartments on both sides of the hallway, like 80% of your square footage is leasable,” she said. “And with a single stair, you’re more at 90%. So less money spent on stuff that isn’t people’s houses.”
It’s also a good way to encourage infill development, which builds in already-developed areas like downtown Chattanooga.
“It really is a story about expanding housing choice and moving regulatory barriers, van Deursen said.
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