Madison's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Madison, Wisconsin, there are 9 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Tiny Homes

Tiny homes on foundations are allowed in Madison if they meet WI Uniform Dwelling Code and zoning minimum dwelling size. Tiny houses on wheels are treated as RVs and not allowed for permanent residence outside RV parks.

Key details: Foundation Tiny: Allowed as ADU or primary. THOWs: Not for permanent residence. Code: WI UDC applies. ADU Option: MGO 28.151. Min Size: Per UDC standards.

Contact your local code enforcement office for specific penalty information.

Carport Rules

Madison treats carports as accessory structures under MGO 28 zoning. Permits are required and setbacks and coverage limits match detached garage rules. Cloth or canopy carports are generally prohibited as permanent structures.

Key details: Code: MGO 28. Setback: 3 ft side and rear. Fabric Canopies: Generally prohibited. Coverage: Counts to 10 percent. Permit: Required.

Unpermitted or fabric carports cited under MGO 28 with forfeitures 150 to 500 dollars plus removal orders.

ADU Impact Fees

Madison does not charge development impact fees on residential ADUs. Wisconsin Statute 66.0617 authorizes municipal impact fees broadly but requires a fee study demonstrating new capacity need. Madison currently imposes only standard building permit fees through the Building Inspection Division. Madison Water Utility charges connection fees only if a new service line is installed.

Key details: Municipal Impact Fees: None on ADUs. State Authority: Wis. Stat. 66.0617. Building Permit: ~1-1.5% of construction. Utility Connection: Only if new service line.

Failure to pay permit fees blocks permit issuance and inspection scheduling. Unpermitted construction triggers MGO 28.183 forfeitures of $100 to $1,000 per offense. Wisconsin DSPS may impose additional penalties for unlicensed plumbing or electrical work. Liens under Wis. Stat. 66.0703 may be filed for unpaid permit and inspection fees.

The rules around adu impact fees in Madison lean permissive, but that does not mean anything goes.

ADU Permits

Madison is one of the Midwest's most ADU-friendly cities. Madison General Ordinances (MGO) Chapter 28 (Zoning Code) permits accessory dwelling units (ADUs) by-right in most residential districts (TR-C1, TR-C2, TR-C3, TR-C4, TR-V1, TR-V2, TR-U1, TR-U2, SR-C1, SR-C2, SR-V1, SR-V2) following the 2013 zoning code rewrite. Permits are filed with the City of Madison Building Inspection Division through the Accela permit portal. Wisconsin Uniform Dwelling Code (SPS 320-325) applies.

Key details: Code Authority: MGO 28.151. By-Right Districts: All TR and SR zones. Max Size: 800 sq ft or 75% of primary. Max Height: 25 feet detached. Filing Portal: Accela Citizen Access.

Unpermitted ADU construction violates MGO Chapter 28 and triggers stop-work orders under MGO 28.183, with daily forfeitures of $100 to $1,000 per offense. Wisconsin DSPS may impose separate penalties for unlicensed plumbing or electrical work under Wis. Stat. 145 and 101.862. Building Inspection may issue raze orders for unsafe structures. Liens may be filed for unpaid fines and corrective work costs.

If you are coming from a city with tighter rules, you will find Madison gives residents more flexibility on adu permits.

ADU Owner Occupancy

Madison does not require owner-occupancy for ADU properties under MGO Chapter 28. Property owners may build an ADU and rent both units to separate tenants. The Common Council removed the owner-occupancy requirement in 2020 amendments to Section 28.151. Wisconsin has no state preemption on owner-occupancy. Condominium and HOA covenants under Wisconsin Statute Chapter 703 may impose private restrictions.

Key details: City Rule: No owner-occupancy required. Removed: 2020 MGO 28.151 amendment. State Preemption: None in Wisconsin. Condo Law: Wis. Stat. Ch. 703.

No city enforcement of owner-occupancy. HOA or condo violations result in declaration-based fines, typically $50 to $500 per violation, with lien rights for unpaid assessments under Wis. Stat. 703.16. Civil litigation in Dane County Circuit Court is available for declaration enforcement.

The rules around adu owner occupancy in Madison lean permissive, but that does not mean anything goes.

ADU Rental Restrictions

Madison allows long-term rental of legal ADUs without special licensing. Short-term rentals (under 30 days) require a Tourist Rooming House license under MGO Chapter 9 and Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) ATCP 72 license. Wisconsin Act 59 (2017) preempts outright STR bans but allows reasonable regulation. Madison's STR ordinance limits non-owner-occupied STRs.

Key details: Long-Term Rental: Allowed (rental registration). STR Licensing: MGO Ch. 9 + DATCP ATCP 72. Non-Owner STR Cap: 30 days/year typical. Room Tax: 9% Madison. Rent Control: Preempted (Wis. Stat. 66.1015).

Operating an unlicensed STR violates MGO Chapter 9 with forfeitures of $100 to $1,000 per offense and may trigger license revocation. Non-owner-occupied STRs exceeding 30 days per year face escalating fines and possible nuisance property designation. Unremitted room tax accrues with city and state collection actions, including liens under Wis. Stat. 66.0703. Repeat violations may result in license suspension or revocation by the City Clerk.

ADU Rules

Madison legalized accessory dwelling units citywide in 2013 under MGO 28.151. ADUs are allowed in all residential districts subject to size, owner-occupancy, and parking standards. One of the first Midwestern cities to embrace ADUs.

Key details: Code: MGO 28.151. Legalized: 2013 citywide. Max Size: 800 sq ft. Owner-Occ: Required. Parking: One space, exemptions.

Contact your local code enforcement office for specific penalty information.

Madison is more permissive than most cities when it comes to adu rules. That said, there are still limits.

Shed Rules

Madison requires a zoning permit for sheds over 150 square feet and a building permit for structures over 200 square feet. Setbacks are typically 3 feet from side and rear lot lines per MGO 28.

Key details: Exempt: Under 150 sq ft. Zoning Permit: 150 to 200 sq ft. Building Permit: Over 200 sq ft. Setback: 3 ft side and rear. Height: 10 ft trigger.

Unpermitted sheds can be ordered removed or retroactively permitted with double fees. MGO 28 forfeitures range from 150 to 500 dollars.

Garage Conversions

Garage conversions to habitable space require a building permit in Madison and must meet WI Uniform Dwelling Code for egress, insulation, and ventilation. Converting to an ADU follows MGO 28.151 with parking replacement if required.

Key details: Permit: Required. Code: WI UDC SPS 320-325. As ADU: MGO 28.151 applies. Parking: Replace if required. Ceiling: 7 ft minimum.

Unpermitted conversions can trigger stop-work orders, double permit fees, and requirement to restore original condition.

The Bottom Line

Compared to many U.S. cities, Madison gives residents more room on accessory structures. 4 of the 9 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

These rules come from Madison's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.