Contra Costa County · Renting & eviction

Rent increases in Contra Costa County

County rule: standard mobilehome space increases are the greater of 2% or 75% of the CPI change in any 12 months, at most 6%. State law: covered units are limited to 8.8% for increases taking effect August 1, 2026 through July 31, 2027. County rule: in condominium conversions, all increases in 12 months may total no more than 100% of the San Francisco-Oakland rental CPI change.

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Key points

Mobilehome spaces: County rule: standard mobilehome space increases are the greater of 2% or 75% of the CPI change in any 12 months, at most 6%.
State rent cap: State law: covered units are limited to 8.8% for increases taking effect August 1, 2026 through July 31, 2027.
Condo conversions: County rule: in condominium conversions, all increases in 12 months may total no more than 100% of the San Francisco-Oakland rental CPI change.

Each rule below links to the section of the Contra Costa County Municipal Code it was read from, with the code text one click away (checked October 2026). General information, not legal advice.

What Contra Costa County's code says

Contra Costa County code What Contra Costa County's code adds
Annual increase limit	No more than 100% of the change in the San Francisco-Oakland rental CPI for the 12 months before filing. Applies: Condominium conversions only; starts when the conversion application is filed; includes subleased units. § 926-14.204 · code text Upon filing an application for conversion, a tenant's residential rent shall not be raised by more than the amount of one hundred percent of the change in the Consumer Price Index - rental component for the San Francisco - Oakland SMS A for the previous twelve-month period prior to filing. The greater of 2% or 75% of the CPI change in any 12-month period, but no more than 6%. Applies: Mobilehome park spaces only; standard annual increase; administration-fee, capital-improvement and certain other increases are separate. § 540-2.404 · code text space rent payable for use or occupancy of any mobilehome space shall not be increased by a park owner within any twelve-month period more than the greater of: (1) Two percent; or (2) Seventy-five percent of the percent change in the Consumer Price Index
Floor or ceiling on the increase	No cap on major rent increases. Applies: Mobilehome park spaces only; major increases are decided on review, which must allow the park owner a fair and reasonable return. § 540-2.1004 · code text No cap shall be placed on rent increases pursuant to this section. No more than 5% of the mobilehome owner's then-existing rent. Applies: Mobilehome park spaces only; any single or combined streamlined capital improvement increase; spread over the improvement's useful life and removed once recovered. § 540-02.408 · code text However, in no event may any single rent increase, or any cumulative rent increases under this section exceed five percent of the mobilehome owner's then existing rent.
Units covered	Only tenants who lived in the unit on the date of the notice of intent to convert. Applies: Condominium conversions only; applies to the lease and rent-limit rules. § 924-14.206 · code text Sections 926-14.202 — 204 shall apply only to tenants who were residents as of the date of notice of intent to convert. Mobilehome spaces covered by the county's mobilehome rent chapter. § 540-2.402 · code text The maximum space rent chargeable for a mobilehome space subject to the provisions of this chapter shall be the base rent.
How often rent can go up	All increases in each 12-month period count together against the CPI limit. Applies: Condominium conversions only; from when the conversion application is filed. § 926-14.204 · code text The rental increase limitation is cumulative within each successive twelve-month period and shall apply to subleased units.
Petitions and pass-throughs	Major increases may rest on unavoidable operating-cost increases, substantial rehabilitation or capital improvements, fair return, and other listed financial factors. Applies: Mobilehome park spaces only; a major rent increase proposed by the park owner. § 540-2.1004 · code text Factors to be considered in evaluating a major rent increase proposed by the park owner include: The park owner may pass through a pro rata share of the allowable percentage of county administration fees. Applies: Mobilehome park spaces only; in addition to the standard increase; not part of base rent; removed once the share is collected. § 540-2.406 · code text a park owner may increase the space rent payable for a mobilehome space within any twelve-month period, in order to apportion and pass through on a pro rata basis, to each mobilehome space subject to the provisions of this chapter, the allowable percentage of county administration fees Instead, a park owner may apply for a major increase, including for capital improvements that would raise rent over 5%. Applies: Mobilehome park spaces only; an alternative to the streamlined capital improvement increase. § 540-02.408 · code text Nothing in this section shall preclude a park owner from foregoing the right to seek a rent increase under this section and instead applying for a major rent increase, including applying for a major increase based on capital improvement expenditures that would otherwise result in a rent increase in excess of five percent of the mobilehome owner's then existing rent.

Also in Contra Costa County's code: Special Leases and Rent Increase (Ch. 926-14) — condominium conversions only; Mobilehome Space Rent (Ch. 540-2) — mobilehome park spaces only. This page does not summarize it yet.

The California rule underneath

Where Contra Costa County's rule above does not cover a situation, state law still applies. For the statewide rule on its own, see California's statewide rent cap.

CA state law The statewide rule underneath
Rent cap right now	8.8% for increases taking effect August 1, 2026 through July 31, 2027 (5% plus 3.8% inflation) Applies: Covered units only. Inflation is the BLS consumer price index for the San Francisco-Oakland-Hayward area, April to April, as the statute requires; the figure is recomputed every year. Civ. Code § 1947.12(a)(1), (g)
Statewide rent increase cap (AB 1482)	5% plus the change in cost of living, or 10%, whichever is lower, over any 12 months Applies: Covered units only; measured against the lowest rent charged in the prior 12 months. Civ. Code § 1947.12(a)(1)
Number of rent increases	No more than two increases in any 12-month period Civ. Code § 1947.12(a)(2)
Rent cap — new construction exemption	Housing with a certificate of occupancy issued within the previous 15 years is exempt (rolling) Applies: Mobilehomes excepted. Civ. Code § 1947.12(d)(4)
Rent cap — single-family home or condo exemption	A home or condo that can be sold on its own is exempt when the owner is not a REIT, a corporation or an LLC with a corporate member, and the tenant was given the written exemption notice Applies: The same exemption applies to the just-cause rule (§ 1946.2(e)(8)). Civ. Code § 1947.12(d)(5)
Rent cap — owner-occupied duplex exemption	A duplex in one building is exempt when the owner lived in the other unit at the start of the tenancy and still does, unless either unit is an ADU or JADU Civ. Code § 1947.12(d)(6)
New tenancy resets the rent	When no prior tenant remains, the owner may set the initial rent; the cap applies to later increases Civ. Code § 1947.12(b)
Rent cap sunset	§ 1947.12 is repealed on January 1, 2030 unless extended Civ. Code § 1947.12(o)

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More on renting & eviction in Contra Costa County

All renting & eviction rules in Contra Costa County

Retaliation in Contra Costa County

California's statewide rent cap

Contra Costa County Municipal Code — full text