Seminole County Just Raised ADU Size Limits — But Sanford’s Historic Districts Play by Different Rules
Seminole County’s new ADU rules raise the maximum size for a detached accessory dwelling unit to 50% of the main home’s footprint, or 1,100 square feet, whichever is less — up from the previous 35% or 1,000 square feet. But if you live inside Sanford city limits, especially in one of its historic districts, these new ADU rules don’t automatically apply to your property.
What Do Seminole County’s New ADU Rules Allow?
Seminole County’s new ADU rules raise the maximum size for a detached accessory dwelling unit from 35% of the primary home’s square footage (or 1,000 sq. ft.) to 50% (or 1,100 sq. ft.), whichever is less. The change applies to unincorporated Seminole County and gives homeowners meaningfully more room to build a mother-in-law suite, guest house, or rental unit. For many lots, the jump from a 1,000 sq. ft. cap to 1,100 sq. ft. is the difference between a cramped studio and a genuinely livable secondary unit.
Do Seminole County’s ADU Rules Apply Inside Sanford City Limits?
No — Seminole County’s new ADU rules apply only to unincorporated parts of the county, not to property inside Sanford city limits. Homes within Sanford fall under the city’s own Land Development Regulations instead, which haven’t automatically changed just because the county updated its code. This is the detail that trips up a lot of homeowners assuming the new rules apply countywide.
What ADU Rules Apply If I’m in a Sanford Historic District?
If your property sits in the Downtown Commercial Historic District, the Sanford Avenue Historic District, the Sanford Residential Historic District, or the Georgetown Historic District, city ADU rules require a Certificate of Appropriateness (COA) from the Historic Preservation Board before any building or clearing permits can be pulled. This COA requirement applies on top of whichever size standards ultimately govern your ADU — it’s a separate layer of review focused on preserving the architectural character of these historic areas, not on square footage.
The Historic Preservation Board reviews larger (“major”) applications in a public meeting held the third Wednesday of each month, while smaller (“minor”) applications can be approved directly by city staff. Either way, this step happens before a building permit is issued, so it’s worth building into your timeline early.
What Do These ADU Rules Mean for Sanford Homeowners?
For homeowners in unincorporated Seminole County, the new ADU rules mean more room to build right away — up to 1,100 sq. ft. instead of 1,000. For homeowners inside Sanford city limits, especially within one of its four historic districts, the new county ADU rules don’t apply directly, and an added Historic Preservation Board approval step comes first. Either way, an ADU can be a meaningful way to add rental income potential or multigenerational living space, and knowing which rules actually apply to your address is the first step in avoiding a permitting delay.
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