West Allis, WI Accessory Structures: ADU Rules (2026)
ADU rules in West Allis, WI, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Limit
- 1 accessory dwelling unit per lot
- Eligible districts
- RA-1-3, RB, RC, C-2-4
- Use classification
- Limited accessory use
- Definition
- Any dwelling unit besides principal unit
Summary
West Allis allows one accessory dwelling unit per lot as a limited accessory use in most residential and several commercial districts, defined as any dwelling unit besides the principal one.
Accessory Dwelling Unit A dwelling unit other than the principal dwelling unit. ... Accessory Dwelling Unit All Permitted up to 1 accessory dwelling unit per lot
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: ?).
Full Breakdown
West Allis Revised Municipal Code § 19.16 defines an accessory dwelling unit as 'a dwelling unit other than the principal dwelling unit.' The § 19.35 accessory-use table lists ADUs as a limited use in the RA-1, RA-2, RA-3, RB, RC, C-2, C-3 and C-4 districts, but not in C-1, I-1, I-2, P or SF. Section 19.36 then caps the use at one accessory dwelling unit per lot: 'Permitted up to 1 accessory dwelling unit per lot.' No conditional use permit is required, but the ADU must still meet the district's normal building size, yard and parking standards.
Violations & Fines
A second accessory dwelling unit on the same lot, or an ADU built in a district where the use isn't listed, such as C-1, I-1, I-2, P or SF, exceeds what the accessory-use table allows.
Frequently Asked Questions
How many accessory dwelling units can I build in West Allis?
Are accessory dwelling units allowed on all West Allis lots?
Sources & Official References
Other rules in West Allis
How West Allis compares: Easiest Cities to Build an ADU·Compare West Allis to another location·View the Wisconsin accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Milwaukee County handle adu rules.