ADU Rules in Biloxi, Mississippi

Biloxi is a Harrison County city on the Gulf of Mexico with a population of approximately 46,000. Famous for its casino resort industry along the Gulf Coast, Biloxi is also home to Keesler Air Force Base. The city was catastrophically damaged by Hurricane Katrina on August 29, 2005 — most historic structures along the waterfront were destroyed by storm surge, and the city was largely rebuilt post-storm. Mississippi has no statewide ADU law — all accessory dwelling unit rules are set by Biloxi's local zoning ordinance.

Mississippi Statewide ADU Law

Mississippi has not enacted statewide ADU legislation. There is no state mandate requiring cities to permit ADUs or streamline approvals. Biloxi's local zoning ordinance governs whether an ADU is permitted on your property, what size it can be, and what coastal, military, and flood standards apply.

Permitted ADU Types

Availability varies by zoning district — verify with the Planning Department. In coastal Biloxi, elevated construction is commonly required:

• Detached ADU: A separate elevated structure on the same lot — typically on pilings in coastal flood zones
• Attached ADU: An addition to the primary home with its own entrance and living facilities
• Upper-Level ADU: Above-flood-level units are especially practical in VE and AE zones
• Garage Conversion: Converting existing structures — must meet current flood elevation standards

Coastal Flood Zones: Critical Considerations

Biloxi is surrounded by water on three sides — the Gulf of Mexico, the Mississippi Sound, and the Biloxi Back Bay — creating extensive flood zone coverage:

VE Zone Construction: Properties along the Gulf shoreline in VE zones require open foundation systems (pilings, piers, or columns). Enclosed spaces below the BFE are extremely restricted. ADU construction in VE zones requires a coastal engineer.

Advisory Base Flood Elevations (ABFEs): After Katrina, FEMA issued ABFEs for Biloxi that are significantly higher than pre-storm standards. The city may require compliance with ABFEs for new construction. Confirm applicable elevations with the Planning Department.

Always check your property's flood zone at the FEMA Flood Map Service Center.

Keesler Air Force Base: AICUZ Overlay

Keesler Air Force Base sits within Biloxi's city limits. The Air Installation Compatible Use Zone (AICUZ) program creates overlay zones around the base based on:

• Noise Contours: Areas within certain decibel ranges (65 dB, 70 dB, 75 dB DNL and above) may have restrictions on new residential construction
• Accident Potential Zones (APZs): Clear Zone (CZ), APZ-I, and APZ-II areas immediately adjacent to runway ends have varying restrictions on dwelling unit density

Properties within AICUZ overlay zones may face:

• Prohibition or limitation on adding dwelling units (including ADUs)
• Requirement for noise attenuation construction techniques
• Disclosure requirements when selling

Contact the Biloxi Planning Department to determine if your property is within a Keesler AICUZ overlay zone.

Hurricane Wind Standards

Biloxi is in Mississippi's highest-wind coastal zone. ADU construction must meet enhanced wind load standards:

• Hurricane straps and clips: Required at all connections
• Roof design: Must meet coastal wind uplift standards
• Opening protection: Impact-resistant windows and doors or shutters may be required
• Garage doors: Must meet wind pressure ratings for coastal areas

Post-Katrina Rebuilding Context

Most of Biloxi's coastal structures were rebuilt post-2005. If your property was rebuilt after Katrina:

• Your structure may already be elevated on pilings — ADU design must integrate with this foundation
• Existing elevation certificates may be on file with the city
• Substantial improvement: If your ADU project equals or exceeds 50% of the structure's pre-improvement market value, full current flood compliance is required for the entire structure

Zoning Districts and Setbacks

Biloxi's residential setback standards vary by zoning district. Contact the Planning Department for your district's specific requirements. General residential standards typically include:

• Front setback: 20–25 feet minimum
• Side setback: 5–8 feet minimum
• Rear setback: 15–20 feet minimum

Confirm current accessory structure setback standards with the Planning Department.

Height Limits

• Primary residential structures: Typically 35 feet maximum (measured from grade or BFE — confirm which method applies)
• Elevated structures: Height measurement methodology for elevated buildings should be confirmed with the Building Department
• Accessory structures: Generally limited to the height of the primary dwelling

Parking

Contact the Biloxi Planning Department for ADU parking requirements. Typically one off-street space is required per dwelling unit.

Permit Process

1. Flood zone determination: Identify FEMA flood zone and BFE for your property at Flood Map Service Center
2. Confirm ABFE: Ask whether post-Katrina ABFEs apply to your address
3. AICUZ check: Ask the Planning Department whether your property is in a Keesler AICUZ overlay zone
4. Zoning verification: Confirm ADU eligibility in your zoning district
5. Elevation certificate: Obtain or locate any existing elevation certificate
6. Coastal engineer: For VE or AE zone properties, retain a Mississippi-licensed engineer with coastal experience
7. Site and construction plans: Prepare plans showing elevations, setbacks, structural details, and wind load compliance
8. Building permit application: Submit to the Planning/Building Department
9. Inspections: Required at foundation, framing, and final stages
10. Updated elevation certificate: Often required after construction
11. Certificate of Occupancy: Required before occupying the ADU

Contact

City of Biloxi Planning Department 140 Lameuse Street, Biloxi, MS 39530 Website: biloxi.ms.us/departments/planning

Municipal Code: library.municode.com/ms/biloxi

Disclaimer: Mississippi has no statewide ADU law. This guide provides general information about ADU rules in Biloxi and should not be relied upon as legal or regulatory advice. Coastal flood zones, wind standards, and the Keesler AICUZ overlay create a complex regulatory environment — always consult a licensed engineer and verify current requirements with the City of Biloxi Planning Department before making any development decisions.