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St. Lucie County, FL Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified July 2026

ADU rules in St. Lucie County, FL, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Separate ADU use: Not defined in county LDC
Accessory structure cap: 35% of building area
County citation: SLC LDC 8.00.02(B)
Florida ADU statute: F.S. 163.31771
Cities: Port St. Lucie / Fort Pierce differ

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Florida under recent ADU streamlining laws. The St. Lucie County, FL rules below cover local size, height, and setback requirements.

Summary

The St. Lucie County Land Development Code has no separate ADU or guest-house use; a second living unit is treated as an accessory structure and is capped in size. Florida law (F.S. 163.31771) lets counties choose to allow ADUs in single-family zones.

City-specific rules exist: Port St. Lucie has its own adu rules rules that differ from St. Lucie County's county-level regulations. If you live in Port St. Lucie, check the city-specific page instead.

A local government may adopt an ordinance to allow accessory dwelling units in any area zoned for single-family residential use.

View official code

Full Breakdown

St. Lucie County's Land Development Code (LDC) does not define an accessory dwelling unit or guest house as a distinct use for unincorporated land. A detached structure is regulated under Chapter VIII as an accessory structure, and per LDC 8.00.02(B) no accessory structure in a residential zoning district may occupy more than thirty-five percent of the lot's maximum permitted building area. Whether a fully independent second dwelling is allowed depends on the underlying zoning district. Florida Statute 163.31771 separately authorizes any local government to adopt an ordinance permitting ADUs in single-family zones, often tied to affordable-rent affidavits. Confirm current rules with St. Lucie County Planning; incorporated Port St. Lucie and Fort Pierce set their own ADU codes.

Violations & Fines

Building or renting an unpermitted second dwelling is a Land Development Code violation enforced by St. Lucie County Code Compliance under Chapter XI, with notices, daily fines, and Special Magistrate liens until corrected.

Frequently Asked Questions

Can I build a guest house on my St. Lucie County lot?

It is treated as an accessory structure, not a separate dwelling, and cannot exceed 35% of your lot's permitted building area. Independent living units depend on your zoning district. Verify with county Planning first.

Does Florida require St. Lucie County to allow ADUs?

No. Florida Statute 163.31771 lets a local government choose to allow accessory dwelling units in single-family zones, but adoption is optional. St. Lucie County has no separate ADU category in its Land Development Code.

Sources & Official References

Other rules in St. Lucie County

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All St. Lucie County rules

How St. Lucie County compares: Easiest Cities to Build an ADU·Florida rules heatmap·Compare St. Lucie County to another location·View the Florida accessory structures overview

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ADU Rules in Cities Across St. Lucie County

Port St. Lucie, FL