Spring Hill, FL Accessory Structures: ADU Rules (2026)

Hernando County Code Appendix A defines an Accessory Dwelling Unit as 'an additional living space that is an attached addition to an owner-occupied single-family detached home meeting the standards herein.' Critical limitations on Spring Hill ADUs: (1) Attached only — the ADU must be physically attached to the principal single-family home; detached backyard cottages, freestanding guest houses, garage conversions that are physically separated from the main house, and standalone tiny homes are NOT permitted as ADUs in residential districts; (2) Owner-occupied — the principal dwelling must be the owner's primary residence; investor-owned rentals with an added ADU are not permitted; (3) Size cap — the ADU's gross habitable floor area may not exceed 50% of the primary dwelling's gross habitable floor area (a 1,800 sq ft Spring Hill home could have an ADU up to 900 sq ft); (4) One per lot — only one ADU is permitted per principal structure, with a maximum of 2 total dwelling units on the lot; (5) Architectural — the ADU must be architecturally consistent with a single-family residence and may not appear to be a multi-family structure; (6) Entrance — the ADU entrance may be through the main entrance of the principal structure or on the side or rear of the principal structure (not a separate street-facing front entrance); (7) Not for sale or rent to non-family — the ADU 'shall not be sold separately' and is intended as living quarters for non-paying guests of the principal structure owner-occupant (extended family, in-laws, adult children, caregivers). The ADU may contain its own kitchen, bathroom, sleeping area, and laundry to function as a fully independent living space. Florida has no statewide ADU mandate (no equivalent of California AB 68/881 or Washington HB 1110); local control of ADUs is preserved subject only to FS 163.31771 which addresses ADUs as an affordable housing tool but does not mandate them. The Hernando County rule is among the more restrictive in Florida — detached ADUs that would be permitted in some Florida counties (Pinellas, Sarasota, Alachua) are categorically prohibited in Spring Hill. In the AG Agricultural district (10-acre minimum lot) and AR Agricultural-Residential district, a second principal residence is sometimes permitted as a 'guest house' or 'caretaker residence' under separate provisions in Appendix A — but those exceptions do not apply to standard Spring Hill residential lots in R-1A, R-1B, R-1C, R-2, R-2.5, R-3, R-4, RM, or RR districts.