Accessory Structures in Fitchburg, WI

If you live in Fitchburg or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Fitchburg has 3 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

ADU Impact Fees

Fitchburg's zoning code caps most lots at one accessory dwelling unit and bills new utility hookups like a brand-new house: Sec. 22-230(8) charges new water and sewer connections the same fees the city applies to any new residential dwelling unit, with no ADU discount written in.

Key details: ADU cap: One accessory dwelling unit per lot. New utility fee: Same fee as a new dwelling unit. Shared connection: Needs building inspector capacity approval. Size limit: 75% of principal dwelling floor area. Height limit: 25 ft (1-2 family); 30 ft (multifamily).

Building or occupying an ADU utility connection without the building inspector's capacity approval, or without a permit and inspection for new plumbing work, is treated as a code violation enforced by the building inspector and zoning administrator; noncompliant work can be ordered corrected or permitted retroactively before occupancy of the ADU is approved.

Shed & Carport Rules

Fitchburg, Wisconsin caps a detached garage, carport or storage building over 400 square feet at the height of the house and no more than 15 feet under City Code § 22-56(6), while smaller sheds, pet houses and runs under § 22-56(7) cannot exceed 400 square feet and must sit at least four feet off the side or rear line.

Key details: Larger garages/sheds: Over 400 sq ft, § 22-56(6), setbacks apply. Smaller sheds: Under 400 sq ft, § 22-56(7), 4 ft from side/rear. Height cap: No taller than house, 15 feet maximum. Placement rule: Cannot stand forward of front face of house. Lot coverage: Counts toward maximum lot coverage limit.

An accessory building that exceeds 15 feet in height, sits closer than four feet to a side or rear lot line, stands forward of the principal structure's front face, or pushes the lot past its maximum coverage limit violates § 22-56(6)-(7) and is enforced under the citywide penalty schedule in § 1-21: $25 to $500 for a first offense, $50 to $1,000 for a repeat offense within a year, with each day of noncompliance a separate offense.

ADU Rules

Fitchburg allows one accessory dwelling unit per lot under § 22-230, capped at 75 percent of the principal home's floor area and 25 feet in height, built to the state Uniform Dwelling Code, with entrances only on the side or rear and no travel trailers or RVs allowed.

Key details: ADUs per lot: One maximum. Size cap: 75% of principal dwelling floor area. Height cap (SF/duplex lot): 25 ft. Entrance location: Side or rear only. Construction standard: State Uniform Dwelling and Energy Code.

Building or operating an ADU that does not meet § 22-230's standards, including exceeding the one-unit-per-lot cap, using a travel trailer as an ADU, or selling the ADU separately from the principal dwelling, is a Chapter 22 zoning violation. The zoning administrator can issue an enforcement demand and refer uncorrected violations to the city attorney for prosecution or injunctive relief, and § 22-648(d)(2) sets a forfeiture of $100.00 per day. New utility connections installed without proper permitting and inspection under § 22-230(7)-(8) are a separate violation subject to the same penalty structure.

The Bottom Line

Fitchburg's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Fitchburg is broadly strict or permissive.

This guide is based on Fitchburg's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.