ADU Impact Fees in Sacramento County, Elk Grove and Roseville (2026) and What SB 1117 Changes

Most ADU fee guides for the Sacramento area quote the City of Sacramento. If your home is in unincorporated Sacramento County (Carmichael, Fair Oaks, Antelope, Rio Linda, Orangevale and similar areas), in Elk Grove or in Roseville, the fees come from different agencies and are calculated differently. This guide sets out which impact fees apply to an ADU in each, how they are calculated under the published 2026 schedules, and what SB 1117 changes from January 1, 2027.

The short answer

• Everywhere in California, an ADU of 750 sq ft or less, and a junior ADU of 500 sq ft or less, pays no impact fees.
• Above 750 sq ft, state law requires impact fees to be charged in proportion to the size of the main house. That is how Sacramento County, Elk Grove and Roseville describe their ADU fees, so the figure depends on your main house as well as the ADU.
• Sacramento County goes further on several of its own fees: park, library and fire fees exempt ADUs up to 850 sq ft, and multi-bedroom ADUs up to 1,000 sq ft.
• From 2027 (SB 1117), for the first two ADUs on a lot, the proportional fee is charged only on the area above 750 sq ft.
• Because the fee depends on your fee district and the size of your main house, ask for a written fee estimate for your parcel. Each agency publishes how to request one.

How a proportional fee works

A proportional fee starts from what a new single-family home would pay and scales it by the ADU's floor area relative to the main house. SacDOT's Measure A schedule spells it out: the ADU pays the ratio of its floor area to the primary unit's, times the fee the primary unit would pay if newly built. With a 1,600 sq ft main house and a 1,000 sq ft ADU, that is 62.5% of the single-family fee.

SB 1117 keeps the proportional method and narrows the area. From 2027 the same 1,000 sq ft ADU is charged on the 250 sq ft above 750: 250 / 1,600, or about 15.6% of the single-family fee. For the law itself, see What SB 1117 changes for ADU impact fees.

Unincorporated Sacramento County

The County states that ADUs over 750 sq ft are subject to impact fees. Several separate programs apply, each with its own rule:

Fee program	2026 rule for ADUs
Park development fees (8 recreation and park districts, rates effective March 2, 2026)	Exempt: ADUs of 850 sq ft or less, and multi-bedroom ADUs of 1,000 sq ft or less. Larger ADUs pay a share proportional to the main house. Single-family rates run from $7,803 (Mission Oaks) to $11,188 (North Highlands).
Library facilities fee (effective March 2, 2026)	Same 850 / 1,000 sq ft exemption, then proportional.
Sacramento Metropolitan Fire capital facilities fee (effective March 2, 2026)	Same exemption, then proportional to what the main house would pay ($1,693.32 for a single-family home).
Cosumnes CSD fire fee (effective January 2, 2026)	Same exemption; ADU rate $882 (Zone 1) or $753 (Zone 6), or the proportional amount if lower.
Measure A (STA) transportation fee (effective July 1, 2026)	Exempt under 750 sq ft; above that, ADU floor area divided by the main house's, times the new single-family fee ($1,132 to $1,800 by house size).
SCTDF and Transit Impact Fee (table effective April 13, 2026)	Charged by transportation district; the published table lists a per-ADU amount, from $742.90 (Mather) to $10,558.76 (District 3), including the transit fee and admin. Ask the County how the 750 sq ft rule applies to your district.

What this means in practice: a two-bedroom ADU of up to 1,000 sq ft in the County pays no park, library or Metro Fire fee even today. Transportation fees are where most of the County's ADU impact cost sits, and where SB 1117 will matter most from 2027.

The County also offers free Shelf Ready ADU plans (460 to 1,184 sq ft); standard building fees still apply. We cover County ADUs on our Carmichael page.

Elk Grove

Elk Grove's 2026 Development Related Fees booklet (updated January 1, 2026) lists its development impact fees per single-family home, among them a Capital Facilities fee ($5,678), an Affordable Housing fee ($6,354), a Roadway fee ($6,201.37 for a home up to 1,200 sq ft), an Active Transportation fee ($999.82) and a fire fee that varies by zone. For the Measure A transportation fee the booklet states the ADU rule directly: no fee under 750 sq ft, and above that the ratio of the ADU's floor area to the main house's, times the fee for a newly built main house.

State law requires the other impact fees on an ADU over 750 sq ft to follow the same proportional rule. The City may have updated its booklet since January; confirm current rates with Elk Grove Development Services. School fees are collected by Elk Grove Unified ($7.23 per sq ft on the City of Sacramento's 2026 reference sheet) and are not affected by SB 1117. More on building in the city on our Elk Grove ADU page.

Roseville

Roseville publishes its residential development fees in a booklet for July 2026 to June 2027, with traffic and park fees set by fee district, and applies them to ADUs through an ADU Fee Policy: no impact fees under 750 sq ft and, above that, fees in proportion to the square footage of the main house. Because the result depends on your fee district and your main house, Roseville asks owners to request an estimate with its "New Single Family or ADU Development Fee Estimate Request" form. School fees are collected by the school districts on new construction and are separate. See our Roseville ADU page.

What SB 1117 changes in each

Area	Until December 31, 2026	From January 1, 2027 (first two ADUs on a lot)
Sacramento County	Proportional fees on the whole ADU over 750 sq ft; park, library and fire exempt up to 850 / 1,000 sq ft	Proportional fees only on the area above 750 sq ft; the County's wider 850 / 1,000 sq ft exemptions are more generous and remain as published
Elk Grove	Proportional fees on the whole ADU over 750 sq ft	Proportional fees only on the area above 750 sq ft
Roseville	Proportional fees on the whole ADU over 750 sq ft, per the ADU Fee Policy	Proportional fees only on the area above 750 sq ft

Agencies will need to update their schedules and forms; until they do, the statute applies. For the City of Sacramento's numbers, see SB 1117 in Sacramento: ADU impact fees before and after.

FAQ

Why can't I find one ADU fee number for the County?

Because the County's fees come from several programs with different districts, and above 750 sq ft most are proportional to your main house. Two neighbors with different house sizes or in different park districts pay different amounts for the same ADU.

Is a 1,000 sq ft, two-bedroom ADU exempt in Sacramento County?

From the County's park, library and Metro Fire fees, yes: multi-bedroom ADUs of 1,000 sq ft or less are exempt under the 2026 schedules. Transportation fees still apply over 750 sq ft.

Does SB 1117 change school fees in Elk Grove or Roseville?

No. School developer fees fall under the Education Code; SB 1117 only changes impact fees under Government Code 66311.5.

Sources: SB 1117 (Chapter 809, Statutes of 2026) and Government Code 66311.5 as amended; Sacramento County park development fee schedule (rates after March 2, 2026), library facilities and Sacramento Metropolitan Fire development fee notices (effective March 2, 2026), Cosumnes CSD fire fee notice (effective January 2, 2026), SacDOT Measure A (SCTMFP) fee schedule (effective July 1, 2026) and SCTDF/TIF fee table (effective April 13, 2026), Sacramento County Shelf Ready ADU plans; City of Elk Grove 2026 Development Related Fees (updated January 1, 2026); City of Roseville Residential Development Fees July 2026 to June 2027 and Fee Estimate Request form; City of Sacramento School District Impact Fees CDD-0226. Checked October 2026; fees change, confirm with each agency before budgeting.