Two members of City Council are proposing changes to a new zoning classification that's meant to encourage the redevelopment of former industrial sites into mixed-use residential projects.

The category, Industrial Residential Mixed-use (IRMX), was created during the overhaul of the zoning code that culminated when a new code was enacted in 2012. Because it's a new category, it has yet to be mapped into many neighborhoods.

But Councilmen Mark Squilla and Kenyatta Johnson are co-sponsoring a bill that would make a number of changes to the category. The changes would require IRMX projects to include non-residential uses, incentivize artisan or light-industrial uses, reduce the maximum lot coverage, and ease parking and loading regulations.

Why make a bunch of detailed changes to a zoning category that still has to be substantially mapped into neighborhoods?

Matt Ruben, president of Northern Liberties Neighborhood Association, laid out the potential pitfalls of IRMX in a column for PlanPhilly last year.

"IRMX is an odd duck: It allows industrial and residential uses, but it does not REQUIRE an industrial use," Ruben wrote. "So IRMX is a residential developer's dream: It's got the lax zoning rules of industrial property, but it allows for the construction of a 100% residential project."

City planner Andrew Meloney said that the Planning Commission brought the changes to Council in order to prevent IRMX properties from being developed in the way Ruben warned.

"We started noticing that if we were going to zone places [IRMX], there was a real push to just knock things down and build townhomes or something," Meloney said.

Meloney said he couldn't think of any areas where that actually happened, but the writing was on the wall.

Councilman Squilla noticed it, too. He said he'd heard proposals from developers who wanted to build strictly-residential projects in IRMX zones, and he wanted to figure out a way to prevent the new classification from being used that way. He said he wants the category to be used for active mixed-use projects, live-work spaces, artists' studios and things of that nature.

"We think that these changes … help make that a little easier, and make it a little harder to do straight condos," Squilla said.

For his part, Councilman Johnson said his support is partly an outgrowth of the ongoing planning of Washington Avenue west of Broad Street. The corridor is split between two planning districts, and neighbors on both sides have been debating whether to push residential density or commercial uses on the avenue. Johnson said he's hoping to land on a category that accommodates existing industrial businesses and fits in the residential context of surrounding neighborhoods.

"Through the South District planning process we are gathering community input, and the Planning Commission will make formal recommendations regarding Washington Avenue in June," Johnson said in a statement sent to PlanPhilly. "We're hoping to have the IRMX classification ready in the case that the Planning Commission recommends it for Washington Ave."

The bill will go before the Planning Commission for a recommendation next week.

PlanPhilly.com is now a project of WHYY/NewsWorks. It began in 2006 as an initiative of Penn Praxis inside the University of Pennsylvania School of Design. Though now part of WHYY, PlanPhilly still works closely with Penn Praxis in covering planning, zoning and development news.