Understanding the BUILD Act: Impacts on Illinois Municipalities and Counties

3/8/2026

The BUILD Act (HB 5626 - Representative Buckner, D-Chicago), a centerpiece of Governor Pritzker’s affordable housing initiative, represents one of the most aggressive local preemption bills introduced in Illinois in recent years. Mirroring legislation recently enacted in states like Oregon, California, and Utah, the act establishes a "two-track" system designed to mandate urban density while implementing statewide administrative and building code reforms. 

For local officials, it is vital to distinguish between the mandates targeting municipalities versus those impacting county authority. 

The Municipal "Middle Housing" Mandates

The most publicized aspect of HB 5626 is the "Middle Housing" mandate, which primarily targets municipalities rather than unincorporated county land. Under the current text, municipalities would be required to allow increased density "by right" on lots currently zoned for single-family homes.

This density is determined by a sliding scale based on lot size:

  • Small lots (up to 2,500 sq ft): Must allow at least one detached home.
  • Medium lots (up to 5,000 sq ft): Must allow up to four dwelling units.
  • Large lots (over 7,500 sq ft): Must allow up to eight dwelling units.

While these provisions currently serve as amendments to the Illinois Municipal Code and do not yet apply to unincorporated areas, they represent a significant shift in the character of incorporated towns and suburbs.

Additional Municipal Restrictions

The legislation includes two other major provisions currently limited to municipalities:

  • Statewide ADU Legalization: The bill legalizes Accessory Dwelling Units (ADUs), such as "granny flats," statewide. Municipalities would lose the power to ban these units and could only "reasonably regulate" their size.
  • The "Third-Party" Bypass: To accelerate development, the plan sets strict statewide timelines for permit reviews. If a municipality fails to meet these deadlines, developers are authorized to hire qualified third-party firms to conduct inspections, effectively removing local oversight.

Direct Impact on County Authority

While much of the bill focuses on cities, HB 5626 specifically amends the Counties Code (55 ILCS 5) regarding building safety standards.

  • Single-Stairway Building Codes: The proposed language prohibits any county building code from requiring two stairways for residential buildings up to six stories, provided certain safety criteria are met.
  • Preemption of Safety Standards: This is a statewide mandate that removes the ability of a county to set stricter fire safety egress standards for multi-family units in unincorporated areas.

ISACo’s Position and Next Steps

Consistent with the 2026 County Platform, ISACo opposes the provision eliminating local control over building code stairway requirements. We believe it is essential to maintain the authority of local officials to determine appropriate safety standards for their communities.

We will continue to monitor the legislative process for likely amendments and keep counties informed of any changes to the scope of this bill.

 

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