ASHEVILLE, North Carolina — The fourth floor of the new apartment building on Long Shoals Road is designed like the upper levels of countless other rental blocks: A staircase on one end of the floor is connected by a long corridor to another set of stairs at the opposite end. Floor plans with two sets of stairs are mandated by decades-old building-code requirements based on outdated fire-safety concerns. …Eliminating the second-staircase rule would cut construction costs and open up more income–generating living space. …Citing such potential benefits, state Sen. Julie Mayfield, and Sen. Tim Moffitt co-sponsored a bill, that would end the second-staircase mandate for apartment buildings up to 75 feet tall. Firefighting groups oppose the bill, not all local builders are convinced it will be a difference maker, and its progress stalled. …The effectiveness of such features can be seen in New York City and Seattle.