Kankakee County, IL Building Safety: Fire Sprinkler Requirements (2026)
Key Facts
- Amending section
- Sec. 105-211(7), adds IRC R311.7.5.5
- Base requirement
- 1/2-inch gypsum board under interior stairs
- Exception
- Waived if sprinkler system installed
- Not a mandate
- Sprinklers are an exception, not required
- Enforcement
- Sec. 105-131, up to $500/day fine
Summary
Kankakee County does not require residential fire sprinklers outright. Sec. 105-211(7), amending the 2021 International Residential Code, instead waives the county's half-inch gypsum board protection under interior stairs "when an automatic residential fire sprinkler system is installed," giving builders a code-compliance alternative rather than a sprinkler mandate.
Add Section R311.7.5.5 Underside of Interior Stairs. The underside of all interior stairs in new construction are required to be protected with at least half inch gypsum board or equal. Exception: The half inch gypsum board or equal shall not be required when an automatic residential fire sprinkler system is installed.
Full Breakdown
Section 105-211 amends the International Residential Code section by section for construction in unincorporated Kankakee County. " In other words, the county does not mandate residential sprinklers in single-family construction covered by the IRC; it lets an installed sprinkler system substitute for the stair-protection requirement it otherwise imposes. The amendment sits among a wider set of local IRC changes in the same section, including a ban on wood foundations under item (9) and required bolting specifications for attached decks under item (10), all enforced through the same building-permit and inspection process as the rest of Chapter 105: a permit under Sec.
105-66, plan review under Sec. 105-69, and inspection before concealment under Sec. 105-72. Because the sprinkler reference is an exception rather than an independent mandate, there is no separate county section requiring sprinkler installation, coverage area, or system standard; a builder who skips the sprinkler option must instead install the half-inch gypsum protection under the stairs exactly as written.
Violations & Fines
Framing interior stairs without either the required half-inch gypsum board protection or the sprinkler alternative is a Code violation like any other under Sec. 105-131: the code enforcement officer issues a written notice, continuing noncompliance draws a fine of up to $500.00 with each day a separate offense, and the Building Division may suspend the permit under Sec. 105-131(f) until the stairway is brought into compliance.
Frequently Asked Questions
Does Kankakee County require sprinklers in new houses?
What is the underlying rule the sprinkler exception applies to?
Who enforces this stairway protection rule in the county?
Can a builder choose either the gypsum board or a sprinkler system?
Sources & Official References
Other rules in Kankakee County
Compare Kankakee County to another location·View the Illinois building safety overview
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