CHICAGO (WLS) — Chicago lawmakers are divided on legalizing the construction of Accessory Dwelling Units, or ADUs.

These secondary living spaces are illegal to build in most of Chicago, and political gridlock is keeping it that way.

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City officials under three mayors have been pushing for at least six years to unravel the prohibition of AUDs, a term used to describe both coach houses and unused basement or attic spaces that are converted into apartments.

In the legalization campaign, bureaucrats and policy researchers consistently highlight ADUs as a low-risk tool, free to taxpayers, option that has been proven to provide a limited but effective release valve for other cities’ affordable housing crises.

However, many Chicago City Council members remain skeptical of ADU legalization, wary of any move that would limit their ability to guide new development in their wards. That’s one reason why a proposal to legalize the units citywide has been sitting on the shelf for more than a year.

The Illinois Answers Project examined the history of AUDs and the uphill battle to legalize them. You can read more of their reporting at illinoisanswers.org.