Bolthole Index

Santa Clara County, California

Building permits, zoning and septic rules in Monte Sereno, California

Building work inside Monte Sereno, California city limits needs a permit from the City's Building Department, and larger projects go through online plan check1. Monte Sereno sets its own zoning, with R-1-8, R-1-20 and R-1-44 single-family districts2. Septic permits for unsewered property anywhere in Santa Clara County come from the county Department of Environmental Health, and most city lots must connect to sewer34.

At a glance

Building permit
City permit required; minor permits online, larger work through plan check1
Zoning
City zoning: R-1-8, R-1-20 and R-1-44 residential districts2
Minimum lot
8,000, 21,780 or 43,560 square feet depending on district567
Sewer and septic
Sewer required where available; septic permits from Santa Clara County Environmental Health43
Permit fees
Set by a formula tied to the value of the construction8
Accessory dwelling
Allowed on residential lots with Building Official approval; the lot must be on sewer910
Owner-builder
Allowed with an owner-builder declaration for applicants exempt from contractor licensing1111
Floodplain
Development in special flood hazard areas has added requirements12

Who to call

Building permits

City of Monte Sereno Building Department

Building permits, plan checking and inspections inside Monte Sereno city limits (phone is the City Hall main line shown on the page); the Planning Department at cityplanner@cityofmontesereno.org handles land use applications

(408) 354-7635

buildingdepartment@cityofmontesereno.org

18041 Saratoga-Los Gatos Road, Monte Sereno, CA 95030

Septic permits

Santa Clara County Department of Environmental Health, Land Use Program

Onsite wastewater treatment system (septic) permits for new construction and repairs in Santa Clara County where public sewer is not available

Contact details are copied from each office’s official page and were checked against it on October 24, 2026.

Off-grid gear

Going off-grid in Monte Sereno means bringing your own water and power. The kit we’d start with:

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Do you need a building permit in Monte Sereno, California?

Yes. Building work inside Monte Sereno city limits needs a City permit, and the City separates minor permits from permits that need plan checking1. Minor permits are available online for work such as electrical panels, EV chargers, reroofs, sewer line replacement, water heaters and water pipes1. Since January 3, 2024, every new application that needs plan check must be submitted online with plans, an application and a plan-check deposit1. Construction is then inspected on site, and inspections can be scheduled online13. A property owner can apply as owner-builder by declaring an exemption from the Contractors' State License Law on the application11. No final certificate of occupancy is granted until the Fire Department gives the Building Department notice of final clearance for required fire-protection facilities and access ways14.

Who issues building permits in Monte Sereno, and how do you reach them?

The City of Monte Sereno Building Department issues building permits, does plan checking and inspects work inside city limits15. Its front counter and Planning Department share City Hall at 18041 Saratoga-Los Gatos Road; the main line is (408) 354-763515. Inside city limits, Santa Clara County's building department does not issue building permits, because the county's permit rules cover unincorporated land only16. Septic permits are a separate matter and stay with the county3.

What do plan check, permit fees and deposits involve in Monte Sereno?

Permit and plan-review costs in Monte Sereno follow a formula in the California Building Code that depends on the value of the construction8. A plan-check deposit is paid with the online submittal and credited toward the final permit fees1. For a house addition, the City asks the applicant to resolve any zoning or planning issues first, then submit a completed building permit application with plans and calculations to the Building Department17. We could not confirm current deposit and fee amounts, so ask the Building Department for them15.

Does Monte Sereno have zoning, and what does it mean for lot size and setbacks?

Monte Sereno publishes its own zoning districts, including the R-1-8, R-1-20 and R-1-44 Residential Districts2. Minimum lot area is 8,000 square feet in R-1-8, 21,780 square feet in R-1-20 and 43,560 square feet in R-1-44, each unless the slope density formula in the Subdivision Title requires more567. In R-1-8, a single-story house needs a 25-foot front setback and 6-foot interior side setbacks18. In R-1-20 the single-story front setback is 30 feet and the interior side setback is 15 feet19. In R-1-44 the single-story interior side setback is 20 feet20. Setbacks grow with lot area above each district's minimum, and both allowed and proposed structural and impervious coverage must be shown on permit plans21. Accessory dwelling units are permitted on all residential lots with prior approval from the Building Official, but only on a lot connected to sanitary sewer910. We could not confirm a minimum dwelling size or a tiny-home rule for Monte Sereno; ask the Planning Department15.

How do septic permits and sewer work in Monte Sereno?

Most Monte Sereno property is expected to use sewer. Where sewer is available within 300 feet, septic is not the stated alternative, and a property already connected to sewer must show proof of connection before the building permit is issued4. Projects with plumbing work typically also need a permit from the West Valley Sanitation District, with a copy included in the building permit submittal4. Where public sewer is not available, Santa Clara County's Department of Environmental Health permits onsite wastewater systems; for new development its clearance is required before the building permit, and the applicant schedules the required inspections with Environmental Health222324. Cesspools are not authorized anywhere in Santa Clara County25. Soils are a poor match for drain fields: about 1% of Santa Clara County soils lack severe limits for a conventional drain field, so expect an engineered system26.

How do you build a home in Monte Sereno, step by step?

  1. Confirm the lot's zoning district and its lot-size, setback and coverage standards2.
  2. Confirm sewer service; if the lot is unsewered, get Santa Clara County Environmental Health clearance before applying for the building permit2224.
  3. Prepare plans and any geotechnical, hydrology and energy reports the City's submittal checklist requires17.
  4. Submit the application and plan-check deposit online to the Building Department115.
  5. Get a West Valley Sanitation District permit if the project includes plumbing work4.
  6. Schedule inspections online as work proceeds, and expect Fire Department final clearance before a certificate of occupancy1314.

What stays with Santa Clara County, and what should you check before buying in Monte Sereno?

The City decides building permits and zoning inside Monte Sereno, while septic permits for unsewered property stay with Santa Clara County Environmental Health3. Development in special flood hazard areas must minimize flood damage and provide adequate drainage, and manufactured homes and recreational vehicles have extra zone-specific requirements12. Wells are a separate permit: Valley Water requires a permit before anyone digs, bores or drills a covered water well in its service area, and water-supply wells also need County Environmental Health approval first27. Santa Clara County's RV, tiny-home and accessory-dwelling rules apply to unincorporated land, so confirm Monte Sereno's own rules before relying on them16. Typical home values are county-level and high: about $1,624,356 in Santa Clara County28.

Watch-outs

  • Plan-check applications must be submitted online with a plan-check deposit that is credited toward final permit fees1.
  • We could not confirm Monte Sereno rules for wells inside city limits, tiny homes, RV or camping use, driveways, or short-term rentals; ask the Building Department or Planning Department15.
  • Any accessory dwelling unit must sit on a lot connected to sanitary sewer, so an unsewered lot cannot add one10.

Sources

  1. Building and Planning Departments (Monte Sereno), quoted and re-checked
  2. R-1-8 Residential District (Monte Sereno), quoted and re-checked
  3. Onsite Wastewater Treatment System (OWTS), quoted and re-checked
  4. Other approvals that may be needed for construction (Monte Sereno), quoted and re-checked
  5. Monte Sereno Code § 10.05.040—R-1-8 Residential District (Monte Sereno), quoted and re-checked
  6. Monte Sereno Code § 10.05.030—R-1-20 Residential District (Monte Sereno), quoted and re-checked
  7. Monte Sereno Code § 10.05.020—R-1-44 Residential District (Monte Sereno), quoted and re-checked
  8. Monte Sereno Building Department FAQs (Monte Sereno), quoted and re-checked
  9. Monte Sereno Code § 10.06.140—Accessory dwelling units (Monte Sereno), quoted and re-checked
  10. Monte Sereno Code § 10.06.140—Accessory dwelling units (Monte Sereno), quoted and re-checked
  11. City of Monte Sereno Building Permit Application (Monte Sereno), quoted and re-checked
  12. Standards for subdivisions and other proposed development (Monte Sereno), quoted and re-checked
  13. Monte Sereno Building Department FAQs (Monte Sereno), quoted and re-checked
  14. Monte Sereno Code, Chapter 9.01—California Building Standards Code (Monte Sereno), quoted and re-checked
  15. City of Monte Sereno Building Department (montesereno.org)
  16. Apply for a Building Permit, quoted and re-checked
  17. Monte Sereno Building Department FAQs (Monte Sereno), quoted and re-checked
  18. R-1-8 Residential District (Monte Sereno), quoted and re-checked
  19. R-1-20 Residential District (Monte Sereno), quoted and re-checked
  20. R-1-44 Residential District (Monte Sereno), quoted and re-checked
  21. Building Permit Submittal Requirements (Monte Sereno), quoted and re-checked
  22. Other approvals that may be needed for construction, quoted and re-checked
  23. Application for septic/OWTS clearance for new development, quoted and re-checked
  24. Santa Clara County Department of Environmental Health, Land Use Program (deh.santaclaracounty.gov)
  25. Santa Clara County OWTS Ordinance No. NS-517.85, quoted and re-checked
  26. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
  27. Well Permits and Inspections, quoted and re-checked
  28. Typical home value (Zillow): Bolthole Index county data

Written October 24, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

Answers from the rulebook for Monte Sereno

Monte Sereno’s own rules

  • Building permitLimited

    Building work inside Monte Sereno city limits; the City distinguishes minor permits from permits requiring plan checking.

    • Minor permits are available online for listed work such as electrical panels, EV chargers, reroofs, sewer line replacement, temporary power, water heaters, and water pipes.
    • New applications requiring plan checking must be submitted online effective January 3, 2024, with plans, a completed application, and a plan-check deposit fee.
    “Effective January 3, 2024, all new applications for building permits that require a plan check shall be submitted online.”
  • Owner-builder exemptionConditional

    Property owners applying for a Monte Sereno building permit for their own construction activity.

    • Property owner must complete and sign the owner-builder form and provide signature verification acceptable to the issuing agency.
    “I hereby affirm under penalty of perjury that I am exempt from the Contractors’ State License Law for the reason(s) indicated below by the checkmark(s) I have placed next to the applicable item(s)”
  • InspectionsLimited

    Permitted work inside Monte Sereno city limits.

    • The source specifically addresses final roof inspection; inspections for other work were not established by the located material.
    “Always make sure that the City has completed a final inspection of the roof and signed the permit before you make the final payment to the contractor.”
  • Certificate of occupancyLimited

    Development for which a final certificate of occupancy is sought inside Monte Sereno city limits.

    • Required fire-protection facilities and access ways must be completed and approved; Fire Department final clearance notice is required before the final certificate may be granted.
    “No final certificate of occupancy may be granted until the Fire Department issues notice of final clearance of such fire protection facilities and access ways to the Building Department.”
  • Local zoningPresent (with conditions)

    Land inside Monte Sereno city limits.

    • District-specific standards apply.
    “R-1-8 Residential District. [...] Development Standards. The following development standards shall apply in R-1-8 Districts:”
  • Zoning districtsPublished

    Monte Sereno city zoning districts.

    • The fetched official code sections publish at least R-1-8, R-1-20, and R-1-44 Residential District regulations.
    • The fetched selection does not establish that these are the only districts.
    “R-1-8 Residential District. [...] The following development standards shall apply in R-1-8 Districts:”
  • Lot coverageDistrict specific (with conditions)

    Development inside Monte Sereno city limits; structural and impervious coverage are governed by the applicable zoning district.

    • The fetched permit submittal form requires both allowed and proposed impervious and structural coverage to be shown.
    • Numeric coverage limits were not present in the fetched district excerpts.
    “Show total lot area, allowed impervious coverage, proposed impervious coverage, allowed structural coverage, and proposed structural coverage (See Development Standards handout)”
  • Accessory dwellingsAllowed (with conditions)

    Residential lots inside Monte Sereno city limits.

    • Prior application to the Building Official and permit approval are required; ADU standards in § 10.06.140 apply.
    “Accessory dwelling units shall be permitted on all residential lots in accordance with the requirements of this Section.”
  • Off-grid sanitationLimited

    Accessory dwelling units inside Monte Sereno city limits.

    • The limitation is established for ADUs only; no general onsite-sanitation rule was located.
    “The accessory dwelling unit shall be allowed only on a lot or parcel which is connected to sanitary sewers.”
  • Mandatory utility hookupSewer (with conditions)

    New construction and applicable plumbing work inside Monte Sereno city limits.

    • Where sewer is available within 300 feet, septic is not the stated alternative; where a property is already connected to sewer, proof of sewer connection is required before building-permit issuance.
    • Monte Sereno permit submittal requirements state that, when required, a West Valley Sanitation District permit must be obtained, typically for plumbing work.

    sewer availability threshold: < 300 feet (County page states septic is required where sewer is not available within 300 feet.)

    “When required (typically, any project that includes plumbing work), a permit from the West Valley Sanitation District shall be obtained and a copy included with the building permit submittal.”
    One more reviewed finding on this topic
  • Subdividing landRegulated (with conditions)

    Subdivision proposals and other proposed development inside Monte Sereno city limits.

    • Projects larger than 50 lots or 5 acres, whichever is less, must identify SFHA/BFE and proposed lowest-floor and pad elevations; all proposals must minimize flood damage, provide adequate drainage, and protect public utilities from flood damage.
    “All subdivision proposals and other proposed development shall be consistent with the need to minimize flood damage.”
  • Building in a floodplainRequired

    Development, subdivisions, manufactured homes, and recreational vehicles in Monte Sereno special flood hazard areas.

    • Development proposals greater than 50 lots or five acres, whichever is lesser, must identify special flood hazard areas and base flood elevations and provide required elevation and certification information.
    • All development must minimize flood damage, provide adequate drainage, and construct public utilities to minimize flood damage.
    • Manufactured homes and recreational vehicles have additional zone-specific requirements.

    large-development threshold: 50 lots or 5 acres, whichever is lesser (Section 10.21.190(A).)

    “All new subdivision proposals and other proposed development, including proposals for manufactured home parks and subdivisions, greater than fifty (50) lots or five (5) acres, whichever is the lesser, shall: 1. Identify the special flood hazard areas (SFHA) and base flood elevations (BFE).”
  • Permit feesVariable (with conditions)

    Building permits inside Monte Sereno city limits.

    • Permit and plan-review cost depends on construction value; other permit types use the City Council-adopted fee schedule.
    “There is a variable formula in the California Building Code to determine the cost of a building permit and plan review depending on the value of the construction.”
  • Permit processPublished (with conditions)

    House additions inside Monte Sereno city limits.

    • Applicant must first resolve zoning and planning approval issues, then submit a completed permit application with appropriate plans and calculations.
    “If there are no zoning or planning permit issues, you can then submit a completed building permit application along with the appropriate plans and calculations to the City Building Department.”

Rules another office applies inside Monte Sereno

Monte Sereno does not set these itself; the county, a health district or the state does, and they apply to every address inside its limits.

  • Minimum lot sizeSpecified

    R-1-20 Residential District inside Monte Sereno city limits.

    • Alternative minimum required by the slope-density formula may apply.

    minimum lot area: 21780 square feet (or minimum required by slope density formula)

    “The minimum lot area shall be twenty-one thousand seven hundred eighty (21,780) square feet or the minimum as required by the slope density formula as set forth in the Subdivision Title of this Code.”
    2 more reviewed findings on this topic
    • Specified — R-1-8 Residential District inside Monte Sereno city limits.
      “The minimum lot area shall be eight thousand (8,000) square feet or the minimum as required by the slope density formula as set forth in the Subdivision Title of this Code.”
    • Specified — R-1-44 Residential District inside Monte Sereno city limits.
      “The minimum lot area shall be forty-three thousand five hundred sixty (43,560) square feet or the minimum as required by the slope density formula as set forth in the Subdivision Title of this Code.”
  • SetbacksSpecified

    R-1-20 Residential District, single-family buildings inside Monte Sereno city limits.

    • Setbacks increase by five feet for each 10,000 square feet above the minimum lot area.

    front single-story: >= 30 feet · front second-story: >= 40 feet · side interior single-story: >= 15 feet · side interior second-story: >= 20 feet · rear single-story: >= 30 feet · rear second-story: >= 40 feet

    “The minimum front setback shall be as follows: a. Single-story building: Thirty (30) feet. b. Second-story portion of building: Forty (40) feet. [...] The minimum side interior setback shall be as follows: a. Single-story building: Fifteen (15) feet. b. Second-story portion of building: Twenty (20) feet. [...] The minimum rear setback shall be as follows: a. Single-story building: Thirty (30) feet. b. Second-story portion of building: Forty (40) feet.”
    2 more reviewed findings on this topic
    • Specified — R-1-8 Residential District, single-family buildings inside Monte Sereno city limits.
      “The minimum front setback shall be as follows: a. Single-story building: Twenty-five (25) feet. b. Second-story portion of building: Thirty (30) feet. [...] The minimum side setback shall be as follows: a. Single-story building: Six (6) feet. b. Second-story portion of building: Ten (10) feet. [...] The minimum rear yard shall be as follows: a. Single-story building: Thirty (30) feet. b. Second-story portion of building: Thirty (30) feet.”
    • Specified — R-1-44 Residential District, single-family buildings inside Monte Sereno city limits.
      “The minimum front setback shall be as follows: a. Single-story building: Thirty (30) feet. b. Second-story portion of building: Forty-five (45) feet. [...] The minimum side interior setback shall be as follows: a. Single-story building: Twenty (20) feet. b. Second-story portion of building: Forty (40) feet. [...] The minimum rear setback shall be as follows: a. Single-story building: Thirty (30) feet. b. Second-story portion of building: Forty (40) feet.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Monte Sereno or Santa Clara County directly.

  • Minimum dwelling size — Minimum dwelling size inside Monte Sereno city limits.
  • Camping on your land — Temporary camping on private land inside Monte Sereno city limits.
  • Tiny homes — Tiny-home occupancy inside Monte Sereno city limits.
  • Who permits septic — Onsite wastewater systems inside Monte Sereno city limits.
  • Septic permit — Onsite wastewater systems inside Monte Sereno city limits.
5 more unanswered
  • Septic inspection
  • Well permit
  • Agricultural exemption
  • Driveway access
  • Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Unanswered questions are usually a sign that Monte Sereno publishes no rule on the point, not that none exists. Santa Clara County’s page lists the county offices to call.

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