ADU Rules in Madison, WI (2026)
ADU rules, permit requirements, size limits, and fees for Madison, WI. Source-cited from official municipal code.
Whether ADUs are allowed in Madison, WI has not been confirmed — see the official source before proceeding.
Whether Madison, WI permits accessory dwelling units (ADUs) has not been confirmed from an official source. ADUs — also called granny flats, in-law units, or secondary suites — are secondary housing units on a single-family or multifamily lot. Contact the local building department at (608) 266-4551 to verify current ADU rules before proceeding, as regulations may have changed since this data was last reviewed.
ADU Size Limits
ADU Size Limits in Madison: Detached ADU: size varies by zoning — see official source (max height: varies — see official source). Attached ADU: size varies by zoning — see official source.
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | See official source | See official source |
| Attached ADU | See official source | See official source |
Permit Fees
ADU Permit Fees in Madison: Plan check fee: Varies. Building permit fee: Varies. Impact fees: None. School fees: None or N/A. Total estimated permit cost: Varies.
| Fee Type | Amount |
|---|---|
| Plan Check | $100-$500 |
| Building Permit | Based on construction value — typically $700-$3,000 |
| Impact Fees | None |
| School Fees | None |
| Total Estimate | See official source |
Permit Timeline
Madison ADU Permit Timeline: Permit timeline has not been confirmed — contact the department for current processing times. Apply through the local building department online permit portal. Phone: (608) 266-4551.
Setback Requirements
ADU Setback Requirements in Madison: Front setback: follows zone standard. Side setback: no minimum. Rear setback: no minimum.
Parking Requirements
Parking Requirements: Parking requirements have not been confirmed — see official source.
Restrictions & Requirements
- ADU must comply with Madison Building Code habitability standards
- Detached ADU located in rear yard in most transect zones
- Maximum size 1,000 sqft or 50% of principal unit — whichever is less
- Must maintain required transect zone setbacks
- Landmark districts (Third Lake Ridge, Mansion Hill) may require design review
- Shoreland overlay zone near Lake Mendota and Lake Monona has additional restrictions
How Many ADUs Are Allowed?
Number of ADUs Allowed in Madison: Single-family lots: not confirmed — see official source. Multifamily properties: not confirmed — see official source.
- Single-Family Lots
- 1 ADU per lot as of current ordinance
- Multifamily Properties
- ADUs on multifamily parcels reviewed through building permit process
Statewide Preemption
ADU Preemption
We could not confirm a statewide ADU preemption statute for Wisconsin.
View Wisconsin preemption detailsFrequently Asked Questions
Can I build an ADU in Madison?
Yes. Madison, WI allows accessory dwelling units. On a single-family lot you can build 1 ADU per lot as of current ordinance.
How big can an ADU be in Madison?
The maximum size for a detached ADU in Madison is 1,000 square feet.
How long does it take to get an ADU permit in Madison?
The typical ADU permit timeline in Madison is Madison Building Inspection Division: ADU permit review typically 3-6 weeks. Construction 2-8 months. Madison has streamlined ADU permitting to encourage housing supply for the university community.. Total estimated permit fees are $800-$3,500 total permit fees.
Do I need extra parking for an ADU in Madison?
Madison parking rules for ADUs: No additional parking required for ADU in Madison's most urban transect zones (TR-U1, TR-U2). In suburban transect zones, one parking space may be required. Madison's progressive parking policy recognizes transit access as a substitute for on-site parking.
Do I have to live on-site to have an ADU in Madison?
Owner-occupancy requirement in Madison: No owner-occupancy requirement under Madison's ADU rules. Madison's university-driven rental market and progressive housing policy make non-owner-occupied ADUs common.
Source: Madison General Ordinances Chapter 28 (Zoning Code); Madison Building Code. Last verified April 6, 2026. View source