McHenry County, IL Building Safety: Fire Sprinkler Requirements (2026)

McHenry County's Building Code Enforcement Division, part of the Planning & Development Department, administers the 2021 International Residential Code with local amendments adopted under Ordinance O-202211-10-052, effective January 1, 2023. Section 15.08.010 rewrites Section R313 in full. R313.1 states a residential fire sprinkler system 'shall not be required in townhouses,' and R313.2 applies the identical exemption to one- and two-family dwellings. The county went further in the garage provisions of the same amendment package: Section R309.5, titled 'Fire Sprinklers,' is deleted in its entirety, so an attached garage carries no sprinkler mandate of its own either.

A builder who chooses to install a system anyway is not left without a standard. R313.1.1 and R313.2.1 require any voluntarily installed residential sprinkler system, in a townhouse or a one- or two-family home, to be designed and installed to the Illinois Plumbing Code and NFPA 13D. R313.3 covers the far more common case: any home built without sprinklers must still meet the construction and fire-separation requirements the code writes specifically for non-sprinklered buildings, so skipping the system does not relax egress or separation rules elsewhere in the code.

Permits for new single- and two-family construction, including any sprinkler piping a builder chooses to add, run through the McHenry County Planning & Development Department under the same adopted IRC. There is no standalone sprinkler permit or inspection line item because the system itself is optional; inspection instead follows the general residential building permit process for the structure.