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States and cities are loosening building code requirements in an effort to lower construction costs and boost affordable housing.

Some of these changes include allowing low-rise apartment buildings to have just one stairway, reducing how often building codes are updated and rolling back specific electrical or fire safety standards.

But critics have raised safety concerns, noting that existing rules were shaped by past tragedies and aim to prevent future harm.

For example, having only one staircase could allow a developer to add another unit or expand the size of units, said Nicolle Aube, principal and founder of Civex, a planning and civil engineering consulting firm, and an American Planning Association board member.

“But then there’s this flip side, that by removing these codes and protections, it carries this additional risk for the developer and the occupants of the building if the worst-case scenario happens,” she said.

Many states are considering single-stairway apartment laws.

They generally take one of four approaches, said Alex Horowitz, housing policy director at The Pew Charitable Trusts: begin with a study, allow single-stairway buildings statewide, update the state building code while letting local governments opt out, or give localities authority to allow them. Pew has lobbied for and testified in favor of the changes.

Two national developments could make it easier for more states and cities to allow single-stairway buildings, Horowitz said.

The first are proposed updates by the International Code Council, the organization that develops the model codes many states use as the basis for their building rules. An update to its multifamily code, for example, would allow single-stairway buildings to add a fourth story.

Second, the bipartisan 21st Century ROAD to Housing Act moving through Congress would direct the U.S. Department of Housing and Urban Development to develop model guidelines for residential buildings with a single stairway not exceeding six stories.

According to Pew, 19 states and Washington, D.C., introduced bills between 2022 and 2025 to study or allow single-stairway apartment buildings, and seven states passed them in 2025 alone.

This year, Idaho enacted a new law that allows local governments to permit certain apartment buildings to use one stairway — generally up to six stories without an occupiable roof, or five stories with one, along with limits on units per floor, sprinklers, stair width, and smoke and fire detection.

Colorado’s law enacted last year requires certain municipalities to modify their building codes by Dec. 1, 2027, to allow five-story multifamily residential buildings to be served by a single exit. Texas’ 2025 law lets municipalities authorize single-stairway apartment buildings up to six stories.

Colorado state Rep. Andrew Boesenecker, a Democrat who sponsored the new law, came to this issue because the state needed to find a way to make smaller multifamily projects more feasible. He said the policy can help on infill lots where a traditional two-stairway apartment building may not fit.

“Single stairway or smart stairway buildings are not only a very safe way to build multi-family housing, they also bring a product to market that’s just not being offered,” Boesenecker said.

Colorado is one 16 states without a statewide building code, making local implementation a major focus. Boesenecker said lawmakers had to look at “ways that you can make it feasible through local governments to adopt this standard into their building code.”

He said the work to get the support of those skeptical of single-staircase legislation happened a year prior to the bill’s passage, when lawmakers worked with fire chiefs, fire marshals and firefighters’ unions for about a year to get them to a “neutral position” on the bill.

In Texas, Democratic state Sen. Nate Johnson said the law he sponsored will allow for architectural innovation as well as maximizing multi-family housing on odd-shaped and smaller lots.

Johnson said modernizing building codes does not come at the risk of safety.

“Who knows what policies once served well and now, after decades of technological advances and changes in land use, impede good design?” Johnson said. “We have regulations for a reason, and I’m not for throwing out what protects the public. Markets tend to easily meet the challenges of sound regulatory protections.”

Lawmakers in Illinois, New York and Rhode Island considered single-stairway bills this year, but none passed before the legislatures adjourned for the year.

But moving in the opposite direction, Connecticut lawmakers this year repealed the single-stairway law they had passed in 2024, after objections from fire safety officials.

Beyond staircases, Horowitz, of Pew, said this year saw the first legislative sessions in which states have taken a look at elevators to reduce building costs. Washington state enacted a new elevator law this year that directs the state’s Building Code Council to allow smaller apartment buildings, with at most six stories and 24 units, to use smaller and less expensive passenger elevators.

Maine removed some elevator-related requirements, including for certain smoke and draft equipment and for two-way emergency video communication systems inside elevators.

Research by the Center for Building in North America, a nonprofit research group that co-authored Pew’s single-stairway report, found that installing elevators in the United States and Canada is at least three times as expensive as in Western Europe or East Asia. U.S. and Canadian installations start around $150,000, compared with roughly $50,000 in several high-income countries, the group found.