Clinton council adopts updated ADU rules with fire-code reference; one member votes no

Clinton City Council on March 25 adopted Ordinance 25-01Z, updating city rules for accessory dwelling units (ADUs) for internal, attached and detached structures. The ordinance establishes that ADU livable square footage cannot exceed 50% of the primary dwelling’s livable space or 1,500 square feet, clarifies that parking and non-habitable storage are not counted toward that livable-space cap, requires additions or expansions that convert an existing accessory structure into a detached ADU to meet current setback and height standards, and adds a requirement that ADUs meet applicable fire code as approved by the fire department.

The ordinance responds to public comments and a follow-up work session after a March 11 hearing and was approved following a motion that referenced handouts and staff edits made at the March 11 meeting. Council members discussed several specific points before voting, including how to treat garages and workshops when an ADU is attached to or combined with accessory structures, how to treat existing accessory buildings that are converted to living space, and how to ensure adequate fire access.

Why it matters: The changes aim to expand housing options while limiting impacts on neighborhood character and safety. Council members and staff said the revisions were intended to be clearer about how lot coverage and livable-square-foot limits interact, to avoid unintended outcomes such as large garages being counted as ADU living area, and to make explicit that applicants must meet fire and building codes.

Key points and supporting details - Size limit: The ordinance explicitly limits ADU livable square footage to 50% of the primary dwelling’s livable space, up to a maximum of 1,500 square feet; parking and non-habitable storage are excluded from the livable-space calculation. (Footnote 4 in table 3.27.1.) - Garages and site coverage: Council and staff clarified that the ADU livable-space cap applies to living area, while site coverage rules (the 25% lot-coverage threshold referenced in the code) continue to count detached structures and any garage area when calculating combined rear/side yard coverage. The council directed staff to make the wording consistent between the ADU-size provisions and the 25% lot-coverage language so that a garage is not inadvertently excluded from lot-coverage calculations. - Additions to existing accessory buildings: The council added language that any additions or expansions to an existing accessory structure intended for conversion to a detached ADU must adhere to current setback and height requirements; existing footprints may remain but any new construction must meet current code. The council removed a redundant sentence from the draft motion that might have confused readers about the treatment of expansions. - Fire and safety: Councilmembers and the fire chief noted the International Fire Code (IFC) provisions that affect detached ADUs, including the typical 50-foot maximum distance for fire apparatus access to portions of a structure and maximum hydrant distances (500 feet to a front entrance). The final motion adds a plain-language reference requiring ADUs to meet applicable fire code and states that compliance is subject to fire-department approval.

Public input and staff review: The council heard from residents during the continued public hearing. Speakers raised issues including livable-area limits for very large lots, the expense of sewer connections for deep lots, and how height rules interact with roof pitch and neighborhood context. Staff (planning) and the city manager responded with clarifications: detached garages and ADUs will be reviewed against both site-coverage and livable-area rules; sewer connections must meet plumbing and building requirements (ejector pumps are an option, and private solutions remain the owner’s responsibility); and the fire department will be part of site-plan and permit review.

Council action: A motion to adopt Ordinance 25-01Z, with the handout edits and additional council-directed clarifications (adding subsection c on page 3, changes to footnote 4 of table 3.27.1, and a fire-code reference after section 3.d) was moved and seconded. The council voted to approve the ordinance; one council member voted no, citing a desire for additional public input. Staff said they will implement the clarified language in the ordinance exhibits and return the finalized text for recordation.

What happens next: Staff will incorporate the council’s wording clarifications into the ordinance exhibits (table 3.27.1 footnote and the new subsection on expansions), add the fire-code reference with the specific IFC/IRC citations, and coordinate permit and inspection processes with the fire department. Councilmembers asked staff to track ADU permit activity as part of the city’s required moderate-income housing reporting so the council can revisit the code if unintended impacts arise.

Sources: Public hearing testimony (resident Jack Wood and Laurie Miller), planning staff presentations and handouts, comments from the fire chief and city manager, and the council’s motion on March 25, 2025.