ADU rules in Martin County, FL — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Martin County adopted a comprehensive-plan amendment on February 24, 2026 to permit accessory dwelling units (ADUs) on single-family lots, replacing the older 'guest house' term. ADUs are capped at 850 square feet (or half the primary dwelling area, whichever is less) and must be built on a concrete foundation or slab.
Following the 2026 comprehensive-plan change and ongoing Land Development Regulations (LDR) amendments, ADUs are permitted on lots with a detached single-family home or townhouse (not duplexes). Key standards: maximum 850 sq ft or 50% of primary dwelling, whichever is less; must be on a concrete foundation/slab; must be located in the rear or side yard of the principal dwelling; cannot be sold separately from the primary residence; must meet zoning district setbacks. 'Employee dwelling units' are a separate category for nonresidential lots — used by the owner or an employee of a nonresidential establishment on the same lot. Per Fla. Stat. 163.31771, the county must allow ADUs in any area zoned for single-family residential use.
Building or occupying an unpermitted ADU is a code enforcement and building-code violation. Stop-work orders, daily civil fines (up to $250/day first, $500/day repeat under Fla. Stat. 162.09), and required removal may apply.
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See how Martin County's adu rules rules stack up against other locations.
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