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Tehama County, CA Accessory Structures: ADU Rules (2026)

Some Restrictions

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

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

Key Facts

Zones allowed: R-1, RE, AG-1–AG-4, NR
Detached ADU max: 1,200 sq ft
Attached ADU max: 50% of home, up to 1,200 sq ft
ADUs per lot: One
State law: Overrides stricter local terms

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 Tehama County, CA rules below cover local size, height, and setback requirements.

Summary

Tehama County Code § 17.08.050 lets one attached or detached ADU go on an R-1, RE, AG-1 through AG-4, or NR lot with an existing single-family home, capped at 1,200 square feet: subject to more permissive state ADU law.

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

"One attached or detached ADU may be established on all lots that are occupied with a single family dwelling unit and zoned residential or any lot that has an existing legally established permitted single family dwelling...2. The lot is zoned R-1, RE, AG-1, AG-2, AG-3, AG-4, or NR...5. The increased floor area of an attached ADU shall not exceed 50 percent of the existing living area, with a maximum increase...of one thousand two hundred square feet. 6. The total area of floor space for a detached ADU shall not exceed one thousand two hundred square feet."

View official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 23).

Full Breakdown

Under § 17.08.050(A), a lot zoned R-1, RE, AG-1, AG-2, AG-3, AG-4, or NR that already carries a legally permitted single-family dwelling may add one attached or detached ADU. A detached unit is capped at 1,200 square feet; an attached unit can't add more than 50% of the existing living area, also capped at 1,200 square feet. The ADU must meet the same height, setback, lot-coverage, and health standards as ordinary residential construction, with adequate sewer and water service. This is an unincorporated-county rule, adopted in 1998: it doesn't reach Red Bluff, Corning, or the City of Tehama, and California's ADU statute (Gov. Code §§ 66310-66342) overrides any part of it that's more restrictive than the state's own standards.

Violations & Fines

Building or renting an ADU that doesn't meet these standards, or without the required building permit, is a zoning and building-code violation, prosecutable as a misdemeanor under the county's general penalty, § 1.04.042.

Frequently Asked Questions

Can I put an ADU on agricultural land in Tehama County?

Yes: the county's own zoning code allows one ADU on AG-1 through AG-4 lots that already have a single-family home, under § 17.08.050(A)(2).

Does this 1998 ordinance still set the real limits?

Only where it isn't more restrictive than California's ADU law, Gov. Code §§ 66310-66342, which sets a statewide floor local rules can't go below.

Sources & Official References

[1]Tehama County Code (Municode)

Other rules in Tehama County

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All Tehama County rules

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

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