Redwood City, CA Accessory Structures: ADU Impact Fees (2026)
Key Facts
- Fee exemption threshold
- Under 750 sq ft
- 750 sq ft or larger
- Proportional fee to primary dwelling
- Excluded from "impact fees"
- Utility connection and capacity charges
- Prerequisite
- Adequate water/sewer service confirmed
- Standard ADU cap
- 850 sq ft (1,000/1,200 with exceptions)
Summary
Redwood City charges no impact fees on any accessory dwelling unit or junior ADU smaller than 750 square feet. Above that size, impact fees are charged proportionately to the ADU's square footage relative to the primary dwelling, and utility connection fees and capacity charges are not counted as "impact fees" at all.
K.Utilities and Impact Fees.1.No junior accessory dwelling unit or accessory dwelling unit shall be permitted if it is determined that there is not adequate water or sewer service to the property.2.No impact fees shall be imposed on a junior accessory dwelling unit or accessory dwelling unit that is less than seven hundred fifty (750) square feet in size. For purposes of this Article, "impact fees" shall not include utility connection fees or capacity charges.3.For accessory dwelling units that are seven hundred fifty (750) square feet or more, impact fees shall be charged proportionately in relation to the square footage of the primary dwelling unit.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Zoning Code: Supplement 29 | City Code: Supplement 61 Update 1).
Full Breakdown
3(K) governs utilities and impact fees for both accessory dwelling units and junior accessory dwelling units. " The section carves the term narrowly, specifying that "for purposes of this Article, 'impact fees' shall not include utility connection fees or capacity charges," meaning those charges can still apply to a small ADU even though development impact fees cannot. Once an ADU reaches 750 square feet or larger, the exemption ends and "impact fees shall be charged proportionately in relation to the square footage of the primary dwelling unit," rather than at the flat rate applied to a standalone new home.
3(C)(5)), a large share of ADU projects clear the size threshold and owners should expect a proportional fee calculation, not a full waiver, once they build past 750 square feet. The exemption applies City-wide in any zoning district where ADUs are permitted under Article 37, without a separate application.
Violations & Fines
There is no separate penalty tied to § 37.3(K) itself; the consequence of misapplying it is a fee dispute handled administratively through the building permit process, and any ADU built without adequate water or sewer service, or that evades a properly calculated proportional fee, is treated as a Zoning Ordinance violation subject to Article 50's infraction fines of up to $100 to $500 per offense, with each day a separate violation.
Frequently Asked Questions
Does Redwood City charge impact fees on ADUs?
What fee applies once an ADU is 750 square feet or bigger?
Are utility connection fees included in the ADU fee exemption?
Can water or sewer capacity block an ADU permit?
Sources & Official References
Other rules in Redwood City
California rules heatmap·Compare Redwood City to another location·View the California accessory structures overview
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