Verify locally. Mississippi has no mandatory statewide building code. The Mississippi Building Code Council adopts a discretionary IRC minimum (2021 IRC effective July 1, 2024; 2024 IRC effective May 18, 2026), but cities and counties decide whether to enforce it — many rural counties have no permit process for one- and two-family homes. The six coastal counties (Hancock, Harrison, Jackson, George, Pearl River, Stone) must enforce coastal wind/flood provisions. Electrical, plumbing and HVAC are licensed trades. Always verify with your local building department (e.g., City of Jackson). ADU rules below are drawn from official sources — always confirm with the issuing building department before designing or building.
ADU permit rule
ConditionalCase by casecity authority
Fee basis
Where a jurisdiction enforces a code, fees follow that city/county schedule; many rural counties have no permit fee because no code is enforced. Verify locally.
Typical timeline
Varies — only applies where your city/county has adopted a building code.
Setback
—
Area threshold
Not size-exempt
Exempt if
Not exempt
Go / no-go
case-by-case
Mississippi has no mandatory statewide building code. Whether an ADU needs a permit depends entirely on whether your city or county has adopted and enforces a residential code, plus local zoning. Confirm with your local building department.
Do I need a permit to build an ADU in Mississippi?
Per Mississippi rules, an ADU is "conditional" for a permit and the authority is "city". Mississippi has no mandatory statewide building code. Whether an ADU needs a permit depends entirely on whether your city or county has adopted and enforces a residential code, plus local zoning. Confirm with your local building department. Always confirm with the issuing building department.
How big can an ADU be in Mississippi?
Size limits for an ADU in Mississippi are set by local zoning — verify with your city building department.
What are the ADU setbacks in Mississippi?
Setback rules vary by city in Mississippi; confirm with the local planning or building department.
How much does an ADU permit cost in Mississippi?
Fee basis: Where a jurisdiction enforces a code, fees follow that city/county schedule; many rural counties have no permit fee because no code is enforced. Verify locally.
