ADU Permit Requirements in Union, IL
Village of Union handles its own building permits (McHenry County only covers unincorporated areas, not incorporated villages). Building Inspector is available one hour per week, Tuesdays 3 PM to 4 PM. The village has not published its adopted residential code edition online; rules below use IRC 2021 as baseline (the most common adoption in the Chicago metro). No published fee schedule, no online application portal. Apply in person during Village Hall hours or email permits@unionillinois.org. Illinois state plumbing code (IDPH-licensed plumbers) and electrical licensing requirements apply regardless of local code adoption.
By Joey, Founder · Last verified April 18, 2026 · How we research →
When you need a ADU permit in Union
A detached accessory dwelling unit (ADU) is a new dwelling under 2021 IRC and requires a building permit in Union, IL with full sub-permits, zoning review, and an evaluation of well/septic capacity if applicable. ADUs are not allowed by-right in every village zone. Verify with the Village Building Inspector at (815) 923-4153 (available Tuesdays 3 PM to 4 PM) before starting work.
An attached or interior ADU (basement apartment, in-law suite with kitchen) requires a building permit in Union, IL with sub-permits and zoning review under 2021 IRC. Two-family use may not be allowed in all village zones. Verify with the Village Building Inspector at (815) 923-4153 (available Tuesdays 3 PM to 4 PM) before starting work.
ADU Permit Costs: Union vs. Nearby
| City | Estimated Fee |
|---|---|
| Union | N/A |
| Chicago | $500 – $5,000 |
| Aurora | $500 – $5,000 |
| Joliet | $500 – $5,000 |
Fees shown are estimates based on local building code data. Actual fees may vary based on project scope and valuation. See all Union permit costs →
Zoning Considerations
ADU regulations vary dramatically by state and city. Many states (CA, OR, WA) have preemption laws that override local zoning restrictions. Check both state law and local zoning before designing.
Estimated Project Timeline in Union
Here's a typical timeline for a adu project in Union, IL:
Timeline is based on Union's typical about 2 weeks permit processing time. Actual timelines vary by project complexity, completeness of application, and current department workload.
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Frequently Asked Questions
Contact Union's building department for current ADU permit fee information. Fees typically vary based on project scope and valuation.
It depends on the specifics of your project. Some smaller ADU projects may be exempt from permit requirements, while larger ones typically require a permit. Use our free lookup tool to check your specific situation.
Working without a required permit in Union can result in fines, stop-work orders, being required to remove completed work, and complications when selling your home. It's always best to check first.
Typical approval time for ADU permits in Union is about 2 weeks. More complex projects may take longer if plan review is required.
Learn More About ADU Permits
Read our complete guide covering permit requirements, costs, common exemptions, and the application process.
Read ADU Guide →