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San Luis Obispo County, CA Accessory Structures: ADU Rules (2026)

Some Restrictions

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

ADU rules in San Luis Obispo County, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Code Section: Title 22, § 22.30.470
Authorizing Ordinance: Ord. No. 3409 (2020)
Max Size (one ADU): 1,200 sq ft
Min Side/Rear Setback: 4 ft (detached)
Parking: None required
Short-Term Rental: Prohibited (under 30 days)

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 California under recent ADU streamlining laws. The San Luis Obispo County, CA rules below cover local size, height, and setback requirements.

Summary

Unincorporated San Luis Obispo County permits an accessory dwelling unit (ADU) on any lot with an existing single-family dwelling under Title 22 Section 22.30.470, with a maximum size of 1,200 sq ft, minimum 4 ft side/rear setbacks for detached units, and no off-street parking required.

These county ordinances apply to unincorporated areas of San Luis Obispo County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

Maximum size of accessory dwelling. 1,200 square feet, including attics greater than six feet in height, unconditioned storage space, and lofts... Detached accessory dwellings shall comply with the same setback requirements pertaining to distance from property lines or alleys for residential accessory buildings and structures in Section 22.10.140 (Setbacks), however, minimum setback requirements for detached accessory dwellings shall not exceed four (4) feet from side and rear lot property lines... No off-street parking spaces are required for accessory dwellings.

Source: SLO County Planning - Accessory Dwelling Units (program page)View official code

Full Breakdown

470 (Residential - Accessory Dwellings), as amended by Ordinance No. and are subject to ministerial review without discretionary review or public hearing. 1. ' Attached ADUs follow the primary dwelling setbacks. No off-street parking is required for the ADU itself, and existing parking demolished or converted to create the ADU is not required to be replaced. ADUs may be rented for 30 days or more but rental for less than 30 days is prohibited. The ADU may not be sold separately from the primary dwelling. ADUs are allowed (P, permitted) in the AG, RL, RR, RS, RSF, RMF, OP, CR, and REC land use categories.

Violations & Fines

Building or occupying an unpermitted ADU is a violation of Title 22 enforced by the Department of Planning and Building. Code enforcement can issue notices to comply, stop-work orders, and administrative fines, and unpermitted structures may be required to be removed, brought into compliance, or returned to their permitted use.

Frequently Asked Questions

Can I rent my ADU on Airbnb in unincorporated San Luis Obispo County?

No. Per Section 22.30.470(B)(4)(b), rental of an entire accessory dwelling or portion of an accessory dwelling for less than 30 days is prohibited. Long-term rentals of 30 days or more are allowed, but the ADU may not be sold separately from the primary dwelling.

How big can my ADU be?

Up to 1,200 sq ft when established as a single ADU on a lot with an existing single-family dwelling (Section 22.30.470(F)). A detached new-construction ADU built alongside a junior ADU is limited to 800 sq ft and 16 ft in height. ADUs created within an existing accessory structure (e.g., a converted garage) are limited to 1,000 sq ft.

Do I need to provide a parking space for the ADU?

No. Section 22.30.470(F)(5)(a) states that no off-street parking spaces are required for accessory dwellings, and existing parking demolished or converted to build the ADU is not required to be replaced.

Sources & Official References

Other rules in San Luis Obispo County

Shed & Carport RulesSome Restrictions Garage ConversionsSome Restrictions Tiny HomesSome Restrictions ADU Rental RestrictionsSignificant Restrictions Parking Rules: Abandoned VehiclesSignificant Restrictions Animal Ordinances: BeekeepingSome Restrictions Landscaping Rules: Native PlantsFew Restrictions Special Events & Permits: Parade PermitsLight Restrictions Gambling & Gaming: Card Room LicensingSignificant Restrictions Local Taxes & Fees: Business Tax ClassificationSome Restrictions

All San Luis Obispo County rules

How San Luis Obispo County compares: Easiest Cities to Build an ADU·California rules heatmap·Compare San Luis Obispo County to another location·View the California accessory structures overview

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