Home › ADU Rules by County › St. Johns County
How big a backyard home (accessory dwelling unit) can be in St. Johns County, who can build one, and who to call to confirm — from the county's published rules.
Know your main home's size? Get the exact limit for your lot in seconds.
| ADUs allowed? | Yes, with conditions |
|---|---|
| Maximum ADU size | St. Johns hasn't published an ADU size cap in our records. |
| Minimum lot size | 2 acres (typical) |
| Owner must live on site? | Not confirmed in our records |
| Manufactured home as an ADU? | Often allowed, subject to the county's ADU and zoning rules |
Accessory family units / ADUs allowed in single-family residential zones but generally cannot be rented commercially. Must match the primary home architecturally; parking rules vary by neighborhood. IMPORTANT for this business: a manufactured/mobile home used as an accessory family unit requires a minimum 2-acre lot properly zoned for manufactured/mobile homes. 'Guest houses' may have only limited kitchen facilities, can't be occupied by the same tenant over 30 days/year, and cannot be rented. St. Augustine city is separate.
Source: St. Johns County Land Development Code; verified Jul 2026.
Before You Build
ADU rules are set by each county and city — Florida law (Fla. Stat. 163.31771) lets local governments allow ADUs but doesn't require it — and they can change, so always confirm the current rule with St. Johns County before you build.
Confirm with St. Johns County: 904-209-0675 · zoning department website ↗
Zoning is set locally and changes often. Answers are guidance only, not a permit guarantee. Always confirm with the local building/zoning department before purchase.
Common Questions
Yes, with conditions. Accessory family units / ADUs allowed in single-family residential zones but generally cannot be rented commercially. Must match the primary home architecturally; parking rules vary by neighborhood. IMPORTANT for this business: a manufactured/mobile home used as an accessory family unit requires a minimum 2-acre lot properly zoned for manufactured/mobile homes. 'Guest houses' may have only limited kitchen facilities, can't be occupied by the same tenant over 30 days/year, and cannot be rented. St. Augustine city is separate.
St. Johns hasn't published an ADU size cap in our records.
Our records don't confirm an owner-occupancy requirement for St. Johns County — ask the county zoning department before you buy.
Often yes — many Florida counties allow a manufactured or modular home as an accessory dwelling unit, subject to St. Johns County's ADU size, lot, and setback rules. Confirm with the county for your parcel.
Keep Exploring
ADU rules for all 67 Florida counties · ADU-sized homes in our showroom
We'll confirm St. Johns County's rules for your property and help you pick a home that fits — free.
Start Here