Marin County, CA Building Setbacks & Zoning: Lot Coverage Limits (2026)
Key Facts
- Site Plan Review trigger
- Lot coverage above 75%
- Governing section
- Development Code § 22.52.020(A)
- Lot coverage definition
- § 22.130.030
- Decision maker
- Director or Zoning Administrator
- Separate limit
- FAR set by Table 2-5
Summary
Marin County's Development Code doesn't set a flat maximum lot-coverage percentage by zoning district; instead, Section 22.52.020(A) requires discretionary Site Plan Review any time proposed development would push lot coverage above 75 percent on a single-family residential lot in the unincorporated area.
Lot Coverage. Lot coverage is the percentage of total site area occupied by buildings and other structures, impervious paving and other hard surfaces that have a water runoff factor of 0.5 or more according to the Bay Area Storm Water Management Agencies Association guidelines. Structure/building coverage includes the primary structure, all accessory structures (e.g., carports, garages, patio covers, storage sheds, trash dumpster enclosures, etc.) and architectural features (e.g., chimneys, balconies, decks, porches, stairs, etc.). Structure/building coverage is measured from exterior wall to exterior wall.... The provisions of this Chapter apply under any of the following circumstances: A.Proposed development would increase the lot coverage above 75 percent on a single-family residential lot.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 2026 Update 1).
Full Breakdown
5 or higher under Bay Area Stormwater Management Agencies Association guidelines; that includes the primary residence, every accessory structure such as garages, carports, and storage sheds, and architectural features like chimneys, balconies, decks, and porches, all measured from exterior wall to exterior wall. 020(A) requires Site Plan Review whenever proposed development would increase lot coverage above 75 percent on a single-family residential lot, alongside other triggers such as a driveway over 250 feet in specified districts or development on a paper-street lot. 050, which require the project to be consistent with drainage and stormwater best management practices, hold ground disturbance to a minimum, and retain natural features such as ridgelines, native vegetation, and rock outcroppings.
Homeowners who stay at or below 75 percent lot coverage on a single-family lot, and who aren't otherwise pulled into Site Plan Review by a Master Plan condition, a long driveway, or a paper-street lot, are not required to go through this review for coverage alone; floor area ratio limits set by the applicable zoning district's Table 2-5 remain a separate, additional constraint on how much can be built.
Violations & Fines
Building beyond 75 percent lot coverage on a single-family lot without first securing Site Plan Review approval under Chapter 22.52 is a Development Code violation the Community Development Agency can enforce through a stop-work order or corrective permit process; an applicant denied under the Section 22.52.050 findings must revise the project or apply for relief through the Variance procedure in Chapter 22.54.
Frequently Asked Questions
Does Marin County cap lot coverage at a fixed percentage?
What counts toward lot coverage in Marin?
Who reviews a Site Plan Review application triggered by lot coverage?
Sources & Official References
Other rules in Marin County
California rules heatmap·Compare Marin County to another location·View the California building setbacks & zoning overview
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