Bolthole Index

San Mateo County, California

Building permits, zoning and septic rules in San Mateo County, California

35Index Score / 100
#39 of 58 in California

Unincorporated San Mateo County, California requires a building permit before you erect, enlarge, alter, repair, move or demolish a building or structure12. The county also zones unincorporated land through its own Zoning Ordinance, separate from the zoning that cities like Half Moon Bay or San Mateo set inside their own limits34. Septic systems are permitted separately, by Environmental Health Services, and only about 16.3% of the county's soils have no severe limits for a conventional drain field56.

At a glance

Building permit
Required in unincorporated San Mateo County1
Zoning
Yes — a countywide Zoning Ordinance covers unincorporated land; cities zone separately3
Septic permits
Issued by San Mateo County Environmental Health Services5
Owner-builder
Allowed under state law with conditions; a permit and an owner-builder declaration are still required7
Driveway / encroachment permit
Required for a new or altered driveway in the county road right-of-way; $146–$7628
Minimum home size
One-family dwellings must be at least 18 feet wide; no county minimum floor area was confirmed9
Wells
A drilling permit from Environmental Health Services is required10
RV living
Not generally permanent; temporary occupancy during home construction is allowed in the Chapter 8.20 district11

Who to call

Building permits

San Mateo County Planning and Building Department – Building Division

Building permit applications, plan review and inspections in unincorporated San Mateo County

(650) 599-7310

buildingcounter@smcgov.org

455 County Center, 2nd Floor, Redwood City, CA 94063

Zoning

San Mateo County Planning and Building Department – Planning Division

Zoning determinations, zoning-district information, rezoning and land-use review for unincorporated San Mateo County

(650) 363-1825

planningprojects@smcgov.org

455 County Center, 2nd Floor, Redwood City, CA 94063

Septic permits

San Mateo County Environmental Health Services

Septic (OWTS) permits, site evaluations, and water-well drilling permits for San Mateo County

(650) 372-6200

Floodplain permits

San Mateo County Planning and Building Department – Floodplain Management

Floodplain development permits and Elevation Certificate review for unincorporated San Mateo County; reachable through the Planning Division at (650) 363-1825

Roads & driveways

San Mateo County Department of Public Works

Encroachment (driveway) permits for work within the county road right-of-way in unincorporated San Mateo County

Contact details are copied from each office’s official page and were checked against it on October 16, 2026.

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Do you need a building permit in San Mateo County, California?

Yes. Unincorporated San Mateo County requires a permit before a building or structure is erected, constructed, enlarged, altered, repaired, moved, improved, removed, converted or demolished12. This mirrors state law: California requires a separate permit for each building or structure from the local building official before work starts, and code requirements vary by city and county12. The county's own guidance points applicants to pages 12–18 of its Building Ordinance to check whether specific work is exempt213. California lets an owner build their own home without a contractor license under limited conditions — for example, a homeowner improving a principal residence must have lived there for the 12 months before completion, and cannot have used the exemption on more than two structures in a three-year period — but this only removes the licensing requirement, not the permit714. If a project also needs a planning permit, the planning permit must be obtained before you apply for the building permit, and Design Review, Coastal Zone, Resource Management, Planned Agriculture and hazard-overlay districts always require planning review first15. The county's rules apply to unincorporated land only. Inside Daly City, Redwood City and the Town of Hillsborough, the city issues its own building permits161718. Septic and well permits stay with County Environmental Health Services19. Farm buildings get one carve-out: an agricultural building (a non-residential structure for farm implements, hay, grain, livestock or greenhouses) is exempt from the automatic fire-sprinkler section of the county code, but not from building permits, and the local Fire District may still require sprinklers20.

Who is the San Mateo County building department, and how do you reach them?

The Planning and Building Department's Building Division reviews and inspects construction projects that require building permits in unincorporated San Mateo County, from an office at 455 County Center, 2nd Floor, Redwood City2113. Reach the building counter at (650) 599-7310 or buildingcounter@smcgov.org, and inspections at (650) 599-7311; the office is open Monday through Thursday, 8:00 am to 4:00 pm, closed for lunch from noon to 1:00 pm, and closed Friday through Sunday13. The county's Building Service Fee Schedule took effect April 1, 2026, and a separate Affordable Housing Impact Fee applies to residential projects: a single-family home adds up to 2,500 square feet at no impact-fee charge, while projects over 3,500 square feet of net new floor area pay the fee on the full total22. Zoning questions go to the Planning Division at (650) 363-1825, in the same building23.

Does San Mateo County have zoning?

Yes. The County Zoning Ordinance regulates growth and development across unincorporated San Mateo County, and the county's GIS layer labeled "Unincorporated SMC Zoning" shows a parcel's zoning district324. Cities zone their own land: Daly City, Redwood City, Hillsborough, Woodside, Brisbane and Colma each run their own zoning, so a buyer near a city line should confirm with that city's planning department4252627282930. A parcel can carry a base district plus overlays such as S (development standards), CD (coastal zone) or DR (design review), and must comply with each31. One-family dwellings must be at least 18 feet wide at the narrowest elevation; the replacement ordinance is not yet effective in the coastal zone while it is under Coastal Commission review9. We could not confirm a countywide minimum floor area, so ask the Planning Division23. In the Devonshire neighborhood's S-102 combining district, the code sets a 20,000-square-foot minimum building site, 20-foot front and rear setbacks, 10-foot side setbacks, 25% maximum site coverage and a 30-foot height limit; these are neighborhood-specific, not countywide32333435.

How do septic permits work in San Mateo County?

Septic systems are not handled by the building department — San Mateo County Environmental Health Services administers local oversight of onsite wastewater treatment systems (OWTS) under its Local Agency Management Program, and anyone installing an individual water supply or sewage disposal system needs a permit from Environmental Health first5193637. Inspection staff observe and approve the work whenever a system is installed, repaired, altered or destroyed38. Statewide, California's OWTS Policy lets counties run their own approved local program as long as it stays consistent with state standards, which is what San Mateo County does39. Soils matter here: only about 16.3% of San Mateo County's soils have no severe limitations for a conventional drain field, so most parcels will need Environmental Health's site evaluation before you can count on a standard system, and an alternative or engineered design is common6. A water-well drilling permit also comes from Environmental Health Services; it is non-transferable, authorizes only the recorded well driller, may first require a Coastal Development Permit or exemption determination from Planning and Building, and needs at least 2 full working days' notice before drilling begins10. Sewer connection is a separate track: inside a County-maintained Sewer District, a Sewer Inspection Permit, a sanitary sewer plan review or both may be required40. Where there is no municipal sewer, the county states plainly that a septic system is the only approved way to dispose of sewage and wastewater on your own property41.

Can you live in an RV or tiny home on your land in San Mateo County?

Permanent RV living is not generally allowed in California: RVs are intended for temporary occupancy and ordinarily may be occupied only in mobilehome parks or special occupancy parks unless a local ordinance provides otherwise42. San Mateo County's Chapter 8.20 district does provide a limited construction exception: a mobilehome, travel trailer or RV may serve as temporary living quarters on the same parcel while a permanent dwelling is built or reconstructed, without a planning permit, but it must be removed before the permanent home's Certificate of Occupancy is issued11. That exception is district-specific, so confirm the parcel's zoning with the Planning Division before moving an RV onto the land1123. A tiny home must qualify under an approved building or vehicle classification and be placed where that classification is allowed; otherwise it cannot legally be occupied43. San Mateo County's Farm Labor Housing Loan Program recognizes a tiny home as one possible housing unit, but only for participating rental projects serving eligible very-low-income farm laborers and their families; those projects still must meet Planning and Building, Environmental Health and permit requirements44. The county's RV sites at Coyote Point Recreation Area are camping, not residence: the 4 designated sites are open March 1 through October 31, require reservations, cap a visit at 7 days within any four-week period, and limit RVs to 36 feet4546.

Building a home in San Mateo County: the steps, in order

  1. Confirm the parcel is unincorporated and pull its zoning district(s) through the county's GIS zoning layer2324.
  2. If the site will use a well or septic, contact Environmental Health Services early for a site evaluation3736.
  3. If the parcel is in a FEMA flood zone other than Zone X, plan for an Elevation Certificate at plan check, at framing inspection, and before occupancy47.
  4. Submit the building permit application to the Building Division, filing an owner-builder declaration if you're not hiring a licensed contractor13714.
  5. Pay the Building Service Fee Schedule charges and, for larger homes, the Affordable Housing Impact Fee22.
  6. Complete plan review and pass the required inspections, ending with a Final Inspection before occupancy2113.
  7. If you're building or altering a driveway onto a county road, get an encroachment permit from the Department of Public Works488.

What to check before you buy land in San Mateo County

San Mateo County is expensive and densely settled: the typical home value is about $1,595,764, population density runs around 1,619 people per square mile, and the nearest city of 100,000 or more is roughly 11 miles from the county's center495051. Only 4.6% of the county is federal land, and 51.6% of the land is at 15% slope or less, so terrain deserves a parcel-level review5253. Just 16.3% of soils here have no severe limits for a conventional drain field, so check septic suitability before you fall for a parcel6. Ask the Floodplain Management team whether a parcel sits in a mapped flood zone, since anything but Zone X requires at least a foot of elevation above base flood5455. Planning to split a parcel? Unincorporated land divisions fall under the County Subdivision Regulations; a minor subdivision of up to 4 parcels is listed at roughly 6–8 months and about $14,60056. Planning to rent a coastal-zone home short-term? A permit is required, with a limit of 180 nights a year57. The county gets about 28.7 inches of rain a year, with severe drought in roughly 31.9% of years5859. Budget for an effective property tax rate near 0.6% and a median tax bill around $9,167 a year6061.

Watch-outs

  • Unincorporated San Mateo County requires a one-family dwelling to be at least 18 feet wide, but we could not confirm a countywide minimum floor area; ask the Planning Division to review a compact-home design923.
  • The Chapter 8.20 RV exception lasts only while a permanent home is being built or reconstructed on the same parcel, and the RV must leave before the home receives its Certificate of Occupancy11.
  • Most San Mateo County soils are not well suited to a conventional septic drain field — get a site evaluation from Environmental Health Services before you count on standard septic637.

Sources

  1. Apply for a Permit (2026 county census)
  2. Apply for a Permit, quoted and re-checked
  3. San Mateo County | Zoning (2026 county census)
  4. Get Zoning Information, quoted and re-checked
  5. Land Use, Septic & Wells (2026 county census)
  6. 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
  7. California Contractors State License Board - Owner-Builder Overview (2026 county census)
  8. Driveway Permit, quoted and re-checked
  9. Title 8 – Zoning & Development Code, quoted and re-checked
  10. Land Use, Septic & Wells, quoted and re-checked
  11. San Mateo County Zoning Regulations, quoted and re-checked
  12. Do I need a building permit for my project? (California statewide rule), quoted and re-checked
  13. San Mateo County Planning and Building Department – Building Division (smcgov.org)
  14. Owner-Builder Overview, quoted and re-checked
  15. Apply for a Permit, quoted and re-checked
  16. Daly City: Building Project Inspections (San Mateo County), quoted and re-checked
  17. Redwood City: City Code 9.30 Building permit required (moved buildings) (San Mateo County), quoted and re-checked
  18. Town of Hillsborough: Hillsborough Code 17.52.020 ADU general provisions (San Mateo County), quoted and re-checked
  19. Land Use, Septic & Wells, quoted and re-checked
  20. Title 10 – Building Regulations, quoted and re-checked
  21. Building, quoted and re-checked
  22. Building Permit Fees, quoted and re-checked
  23. San Mateo County Planning and Building Department – Planning Division (smcgov.org)
  24. San Mateo County | Zoning, quoted and re-checked
  25. Daly City: Zoning (San Mateo County), quoted and re-checked
  26. Redwood City: Zoning Code 6.1 Purpose (R-2) (San Mateo County), quoted and re-checked
  27. Town of Hillsborough: Hillsborough Code ch. 17.32 Residential structure size and lot coverage (San Mateo County), quoted and re-checked
  28. Town of Woodside: Woodside Municipal Code 153.107 Residential and commercial zoning districts: permitted, conditional, and accessory uses (San Mateo County), quoted and re-checked
  29. Brisbane: Brisbane Municipal Code §17.06.040 R-1 Development regulations (San Mateo County), quoted and re-checked
  30. Town of Colma: Colma Municipal Code Chapter 5.03 Zoning (San Mateo County), quoted and re-checked
  31. Get Zoning Information, quoted and re-checked
  32. Title 8 – Zoning & Development Code, quoted and re-checked
  33. Title 8 – Zoning & Development Code, quoted and re-checked
  34. Title 8 – Zoning & Development Code, quoted and re-checked
  35. Title 8 – Zoning & Development Code, quoted and re-checked
  36. Land Use, Septic & Wells, quoted and re-checked
  37. San Mateo County Environmental Health Services (smcgov.org)
  38. Land Use, Septic & Wells, quoted and re-checked
  39. Water Quality Control Policy for Siting, Design, Operation and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy) (California statewide rule), quoted and re-checked
  40. Building Permit Requirements, quoted and re-checked
  41. Land Use, Septic & Wells, quoted and re-checked
  42. hcd.ca.gov (California statewide rule), quoted and re-checked
  43. Information Bulletin 2016-01: Tiny Homes (California statewide rule), quoted and re-checked
  44. Farm Labor Housing Loan Program, quoted and re-checked
  45. Coyote Point RV Site Rules & Regulations, quoted and re-checked
  46. Coyote Point RV Site Rules & Regulations, quoted and re-checked
  47. Flood Elevation Certificate, quoted and re-checked
  48. San Mateo County Department of Public Works (smcgov.org)
  49. Typical home value (Zillow): Bolthole Index county data
  50. Population density: Bolthole Index county data
  51. Straight-line distance from the county center to the nearest city of 100,000+ people: Bolthole Index county data
  52. Federal land share: Bolthole Index county data
  53. Share of land at 15% slope or less: Bolthole Index county data
  54. San Mateo County Planning and Building Department – Floodplain Management (smcgov.org)
  55. Flood Elevation Certificate, quoted and re-checked
  56. San Mateo County Subdivision Regulations, quoted and re-checked
  57. Short Term Rental Permit (Coastal Zone), quoted and re-checked
  58. Annual precipitation: Bolthole Index county data
  59. Share of years in severe drought: Bolthole Index county data
  60. Effective property tax rate: Bolthole Index county data
  61. Median property tax bill: Bolthole Index county data

Written October 16, 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.

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Compared with neighboring counties

Like all 6 of its neighbors, San Mateo County requires a building permit for a home.

RuleSan Mateo CountySan Francisco CountySanta Cruz CountyAlameda CountySanta Clara CountyContra Costa CountyMarin County
Building permitRequiredRequiredRequiredRequiredRequiredRequiredRequired
County zoningYesYesYesYesYesYesYes
Septic permitsCounty Env. Health ServicesNot publishedCounty Health Services AgencyCounty Dept. of Env. HealthCounty Dept. of Env. HealthContra Costa HealthCounty Env. Health Services

County locator

San Mateo County in California

35
County map
San Mateo County highlighted among the California counties · colored by Index score

How San Mateo County scores

Seclusion13100% ev.
Self-Sufficiency60100% ev.
Admin Boringness41100% ev.
Durability40100% ev.
Property Autonomy56100% ev.
Carry Cost44100% ev.

Evidence strength: 100%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$1596kTypical home
0.6%Property tax
$12,311Land / acre
28.7"Annual rain
31.9% of yrsSevere drought
0.7 / yr (+0.4)Mid-century 100°F days
63.8 daysMid-century dry spell
2.08" (+7.6%)Mid-century 1-day rain
1.07×Wildfire change factor
100%Forward climate coverage
$1,768Home insurance / yr
3.4% / yrInsurance growth
0.6%Nonrenewal rate
county median (2+ published ZIPs)Insurance basis
6,410,169People within 2 hr
722,806Radius comparison (15 mi)
1,619.1People / sq mi
4.6%Federal land
51.6%Land at 15% slope or less
16.3%Soils rated "not limited" for septic (strict USDA rating)
31,843 acWorkable land screen
175.7 tonsBiomass / forest ac
57.1°FAvg temp

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Cities and towns in San Mateo County

Inside a city or town, that city usually issues building permits and sets zoning; the county’s rules above cover unincorporated land. Septic, wells and floodplain rules usually stay with the county or state everywhere.

Not yet researched: San Mateo

Answers from the rulebook for San Mateo County

What the ordinances and state agencies actually say — one answer per question, each quoted from the official source and independently re-checked.

San Mateo County rules

  • Building permitRequired

    Buildings and structures in unincorporated San Mateo County that are erected, constructed, enlarged, altered, repaired, moved, improved, removed, converted, or demolished.

    • The County page directs applicants to pages 12-18 of the Building Ordinance to determine whether particular work is exempt from a permit.
    • The County states that incorporated cities and towns administer their own permitting; this claim is limited to unincorporated areas.
    “Needed if a building or structure will be erected, constructed, enlarged, altered, repaired, moved, improved, removed, converted, or demolished.”
  • InspectionsRequired

    Construction projects in unincorporated San Mateo County that require building permits.

    • The type and timing of required inspections depend on the building permit type.
    • Inspections generally include initial inspections and a Final Inspection once all work under the permit is complete, before occupancy or use of the impacted area.
    • Each inspection must be scheduled separately.
    “We review and inspect all construction projects that require building permits in the unincorporated areas of San Mateo County.”
  • Certificate of occupancyLimited

    Certificate-of-occupancy issuance for development in FEMA-designated flood zones in unincorporated San Mateo County, excluding Moderate to Low Risk Areas designated Zone X.

    • Applicants in all FEMA-designated flood zones except Zone X must demonstrate compliance with applicable flood-development standards.
    • Habitable and utility areas must be at least one foot above the base flood elevation.
    • Areas below the base flood elevation are limited to garage and/or crawlspace purposes constructed according to currently adopted and enforced building regulations.
    • An Elevation Certificate must be provided at plan check, during construction at framing inspection, and completed and approved at final inspection or before issuance of the Certificate of Occupancy.
    • Additional regulations apply under Chapter 35.5, Flood Hazard Areas, of the Zoning Regulations.

    minimum elevation above base flood elevation: >= 1 foot (applies to habitable and utility areas) · Elevation Certificate stages: plan check; framing inspection; final inspection or before Certificate of Occupancy

    “The Elevation Certificate (EC) is a three step process that must be completed before a certificate of occupancy can be issued.”
  • County-wide zoningPresent (with conditions)

    County zoning ordinance and zoning districts in unincorporated San Mateo County.

    • The County Zoning Ordinance regulates growth and development in the county's unincorporated territory.
    • The county's zoning information page identifies an Unincorporated SMC Zoning layer and states that development must comply with each applicable zoning-district regulation.
    • The County Ordinance Code page states that the replacement ordinance is not yet effective in the coastal zone while under Coastal Commission review.
    “Put a check mark in the check box labeled Unincorporated SMC Zoning to display Zoning Districts.”
  • Local zoningVaries (with conditions)

    Aggregate local zoning across San Mateo County, combining county zoning for unincorporated areas with zoning administered by incorporated municipalities; this claim does not attribute municipal ordinances to San Mateo County.

    • The County source expressly identifies its zoning controls as Unincorporated SMC Zoning.
    • Municipal parcels may be subject to the applicable municipality's zoning regulations rather than the county's unincorporated-area zoning regulations.
    • Within unincorporated areas, applicable parcels may have one, two, or several zoning districts and must comply with each applicable district regulation.
    • The replacement county ordinance is not yet effective in the coastal zone while under Coastal Commission review.
    “Zoning information for properties within the unincorporated County is provided by our Planning GIS program. Detailed instructions are also provided on our website. Zoning information is not provided for properties within city limits; please contact your city's Planning Department for more information.”
  • Zoning districtsPublished

    Zoning districts and related zoning layers for unincorporated San Mateo County parcels.

    • A parcel may have one, two, or several zoning districts.
    • Each zoning layer represents a distinct chapter or section in the County Zoning Regulations.
    • Development must comply with the regulation for each applicable district.
    • The County identifies S districts as containing development standards, R districts as primarily residential, RM, TPZ, and PAD districts as rural, CD as applying to all Coastal Zone areas, and DR as requiring design review standards.

    example zoning districts: RM; TPZ; R-1/S-101; R-1/S-17/DR/CD

    “Put a check mark in the check box labeled Unincorporated SMC Zoning to display Zoning Districts.”
  • Minimum dwelling sizeSpecified

    One-family dwellings in unincorporated San Mateo County under the County Zoning & Development Code.

    • The county rule specifies a minimum width, not a minimum total floor area.
    • The cited County Ordinance Code page states that the ordinance is not yet effective in the coastal zone because it is under Coastal Commission review.
    • The rule applies specifically to one-family dwellings; other dwelling types are not addressed by this claim.

    minimum dwelling width: >= 18 feet (Measured by the narrowest elevation.)

    “All One-Family Dwellings: 1. Shall have a minimum width of 18 feet as measured by the narrowest elevation;”
  • Minimum lot sizeSpecified

    Parcels in any single-family residential district combined with the County S-102 Combining District (Devonshire) in unincorporated San Mateo County.

    • The S-102 standards apply only in a single-family residential district with which S-102 is combined.
    • A parcel may not be divided if the resulting building site would be less than the minimum required to maintain conformity with the district building-floor-area requirements.

    minimum building site area: 20000 sq ft · minimum average building site width: 75 ft

    “minimum building site area shall be 20,000 sq. ft.”
  • SetbacksSpecified

    Development in any single-family residential district combined with the County S-102 Combining District (Devonshire) in unincorporated San Mateo County.

    • The S-102 standards apply only in a single-family residential district with which S-102 is combined.
    • The daylight plane is measured along all setback lines from natural grade; certain architectural features may extend into setback areas under Section 8.340.010.

    front setback: 20 ft · rear setback: 20 ft · side setback: 10 ft

    “8.224.050 - Building Setbacks. The minimum setbacks shall be: Front Setback Rear Setback Side Setback 20 feet 20 feet 10 feet”
  • Lot coverageSpecified

    Development in any single-family residential district combined with the County S-102 Combining District (Devonshire) in unincorporated San Mateo County.

    • The coverage calculation includes buildings, accessory buildings, and structures such as patios, decks, balconies, porches, and bridges that are 18 inches or more above ground.
    • The S-102 standards apply only in a single-family residential district with which S-102 is combined.

    maximum building site coverage: 25 percent · included structures elevation threshold: >= 18 inches above ground

    “The maximum building site coverage area ratio shall be .25 (25 percent) and shall include all: (1) buildings, (2) accessory buildings, or (3) structures such as patios, decks, balconies, porches, bridges, and other similar uses which are eighteen (18) inches or more above the ground.”
  • Building heightSpecified

    Buildings in any single-family residential district combined with the County S-102 Combining District (Devonshire) in unincorporated San Mateo County.

    • The S-102 standards apply only in a single-family residential district with which S-102 is combined.
    • For remodeling costing less than 50 percent of total replacement value, the maximum may increase to 36 feet, determined case-by-case by the Director of Planning and Building.
    • Chimneys, pipes, mechanical equipment, antennae, and other common facilities may extend beyond 28 feet to a maximum of 36 feet as required for safety or efficient operation.
    • Attached or detached downhill-slope garages allowed to extend into the front setback are subject to a 28-foot maximum and additional plate-height and story restrictions.

    maximum building height: 30 ft (Remodeling costing less than 50 percent of total replacement value may increase to 36 feet case-by-case.) · downhill-slope garage maximum height: 28 ft

    “maximum building height shall be 30 feet.”
  • Living in an RVTemporary only (with conditions)

    RV occupancy at the County-operated Coyote Point Recreation Area RV sites.

    • RV sites are open March 1 through October 31.
    • Reservations are required and are made through the San Mateo County Parks online reservation system or by telephone Monday through Thursday.
    • RV camping is permitted only in four designated sites, and sites must be occupied during the reserved stay.
    • No more than eight people and one vehicle may occupy one RV site at any given time; vehicles must be parked at the assigned site.
    • The visit limit is seven days within any four-week period.
    • RV size is limited to 36 feet.
    • Tent camping is not allowed.
    • There are no sewage or wastewater hookups; all sewage and wastewater must be contained.
    • Beer and wine are allowed; hard liquor is prohibited under County Ordinance 3.68.080(t). Smoking is prohibited under County Ordinance 4.96040(c).

    maximum people per RV site: <= 8 people · maximum vehicles per RV site: <= 1 vehicle · maximum visit duration: <= 7 days within any four-week period · maximum RV length: <= 36 feet

    “The limit of visit is seven (7) days within any four-week period.”
    One more reviewed finding on this topic
    • Temporary only (with conditions) — Temporary residential occupancy of mobilehomes, travel trailers, or recreational vehicles as temporary living facilities during construction or reconstruction of a permanent dwelling in the district governed by San Mateo County Zoning Regulations Chapter 8.20.
      “Temporary Living Facilities During Residence Construction (1.10.10) None”
  • Camping on your landAllowed (with conditions)

    Temporary RV camping at the County-operated Coyote Point Recreation Area.

    • Camping is limited to four designated RV sites.
    • Reservations are required.
    • Sites are open March 1 through October 31.
    • The site must be occupied during the reserved stay.
    • The maximum visit is seven days within any four-week period.
    • No more than eight people and one vehicle may occupy a site.
    • RV length is limited to 36 feet.
    • Tent camping is not allowed.
    • Sewage and wastewater must be contained because no hookups are available.
    • Hard liquor and smoking are prohibited under the cited County Ordinance provisions.

    maximum visit duration: <= 7 days within any four-week period · maximum RV length: <= 36 feet

    “RV camping is permitted only in 4 designated sites.”
  • Tiny homesLimited

    Tiny homes used as housing units in projects participating in the San Mateo County Farm Labor Housing Loan Program.

    • Project units must be located in San Mateo County.
    • Project units must be rented to eligible very-low-income farm laborers or farm laborers and their families meeting the program's agricultural-work criteria.
    • All project units must be used as rental housing for farm laborers for the duration of the loan term.
    • All projects must comply with applicable Planning and Building and Environmental Health requirements.
    • All applicable permit requirements apply.
    • The program is subject to funding availability and execution of a loan agreement.
    • The document states it was updated and published on 2025-10-22; this is not treated as an effective date.

    farm-labor agricultural employment: > 20 hours per week average (Eligible farm laborers must also earn at least half their income from agriculturally related work.) · maximum rent and utility allowance: <= 30 percent of gross income (The document states allowances must not exceed 30% of gross income.)

    “A housing unit can be a single-family home, mobile home, tiny home, or modular building.”
  • Who permits septicCounty

    Onsite wastewater treatment systems in San Mateo County.

    • San Mateo County Environmental Health administers local OWTS oversight through the County LAMP.
    • The LAMP operates under the State Water Resources Control Board OWTS Policy and was approved by the San Francisco Bay Regional Water Quality Control Board.
    “As such, it is intended to allow the County to continue providing local oversight of OWTS”
  • Septic permitRequired

    Installation of an individual sewage disposal system in San Mateo County.

    • Environmental Health reviews the application for safety to neighboring properties and surrounding areas.
    • Community members and/or the County Board of Supervisors may also need to approve installation of new systems.
    “All people who install individual water supplies or sewage disposal systems must have a permit from Environmental Health.”
  • Septic inspectionRequired

    Individual sewage disposal systems that are installed, repaired, altered, or destroyed in San Mateo County.

    • Environmental Health observes and approves the work.
    • Review includes the proposed location, soil testing, plans, construction, and safe destruction verification.
    “Inspection staff will observe and approve the work when you need to install, repair, alter or destroy an individual sewage disposal system.”
  • Off-grid sanitationLimited

    Sewage disposal on property where no municipal sewer system exists in San Mateo County.

    • If an area lacks a municipal sewer system, sewage and wastewater must be disposed of on the property.
    • The County page states that the only approved system in San Mateo County is a septic system.
    • A permit from Environmental Health is required for installation of an individual sewage disposal system, and Environmental Health observes and approves installation, repair, alteration, or destruction work.
    “If you live in an area of San Mateo County that does not have a municipal sewer system, you must dispose of sewage and wastewater on your own property. In San Mateo County, the only approved system is a septic system.”
  • Well permitRequired

    Drilling a water well in San Mateo County.

    • Before obtaining a drilling permit from Environmental Health Services, the applicant may first need Planning and Building approval or determination regarding a Coastal Development Permit or Coastal Development Exemption.
    • The permit is non-transferable and authorizes only the recorded water-well driller.
    • At least 2 full working days’ notice is required before drilling begins.
    • At least 2 full working days’ notice is required for pump-test, annular-seal, and final inspections.
    • Permit and inspection fees may apply; the cited procedure states the drilling permit fee covers site examination, annular well-seal verification, and processing time, while pump-test verification requires an additional fee.
    “Once you have received approval from the Planning and Building Department or determine that no CDP or CDX is needed, you’ll need a drilling permit from Environmental Health Services.”
  • Mandatory utility hookupSewer (with conditions)

    Sewer connection and related sewer work for projects located in County-maintained Sewer Districts in unincorporated San Mateo County.

    • The property must be confirmed to be within a County-maintained Sewer District.
    • Depending on the project, a sanitary sewer plan review, a Sewer Inspection Permit, or both may be required.
    • A Sewer Inspection Permit is required for certain construction or modification of sanitary sewer facilities within County-maintained Sewer Districts.
    • The County building-permit page requires sewer and water verification from districts before permit issuance for the listed building-permit application requirements.
    • The cited sources do not establish a general sewer-connection requirement for every parcel in San Mateo County or a general water-connection requirement.
    • For properties within incorporated cities or towns, the applicable local agency may impose additional permit requirements.

    base Sewer Inspection Permit fee: 300 USD (Additional fees may apply depending on the project.) · Sewer Inspection Permit validity: 1 year from issuance (A fee is required to renew an expired permit.)

    “A Sewer Inspection Permit (SIP) is required for certain types of construction or modification of sanitary sewer facilities within County-maintained Sewer Districts.”
  • Agricultural exemptionConditional

    Agricultural buildings subject to San Mateo County Title 10 fire-sprinkler requirements in the unincorporated area.

    • The exemption is from the requirements of the automatic-fire-sprinkler section; it does not establish a general exemption from building permits or other applicable codes.
    • An agricultural building must be a non-residential structure designed and constructed to house farm implements, hay, grain, poultry, livestock, or other horticultural products.
    • Agricultural buildings include places of employment where agricultural products are processed, treated, or packaged, and include greenhouses.
    • Office uses may not exceed 10 percent of total floor area unless the building is provided with an automatic fire sprinkler system throughout.
    • Automatic sprinkler requirements may still apply where required by the local Fire District.
    • All automatic fire sprinkler systems, when required or voluntarily installed, must comply with the currently enforced NFPA-13, NFPA-13D, NFPA-13R, and additional County specifications or supplemental rules.
    • The Building Official may require sprinklers when an alteration, addition, or change in use or occupancy increases fire hazard or threat to life and safety.

    maximum office-use share: <= 10 percent of total floor area (unless the agricultural building is provided with an automatic fire sprinkler system throughout)

    “The following structures are exempt from the requirements of this section: a. Agricultural Buildings. For the purpose of this section, an “agricultural building” is defined as a non-residential structure designed and constructed to house farm implements, hay grain, poultry, livestock, or other horticultural products. “Agricultural buildings” include a place of employment where agricultural products are processed, treated or packaged. Office uses within “agricultural buildings” shall not exceed ten percent (10%) of the total floor area of the building unless such buildings are provided with an automatic fire sprinkler system throughout. “Agricultural buildings” shall include greenhouses.”
  • Subdividing landRegulated (with conditions)

    Division of land, movement of lines between parcels, removal of parcel lines, parcel legality, and subdivisions in unincorporated San Mateo County.

    • The County Subdivision Regulations apply to all or parts of subdivisions in the unincorporated territory of San Mateo County, subject to the exclusions in Section 7003.
    • The regulations supplement and implement the California Subdivision Map Act and supplement the County Zoning and Building Regulations.
    • Exclusions include financing or leasing space within apartment, industrial, commercial, mobilehome, or trailer parks; financing or leasing existing separate commercial or industrial buildings on a single parcel; certain financing, construction, or leasing of commercial or industrial buildings on a single parcel; construction, financing, or leasing of a qualifying second unit, although sale or transfer of such a unit without the entire site remains regulated; mineral, oil, or gas leases; qualifying wind-powered electrical-generation-device leases or easements subject to discretionary action; qualifying agricultural land leases to nonprofit organizations for agricultural labor housing; land dedicated for cemetery purposes; qualifying boundary-line or exchange agreements involving the State Lands Commission or a local agency holding a trust grant of tide and submerged lands; divisions creating four or fewer parcels for removable commercial buildings under 100 square feet; separate assessments under Revenue and Taxation Code section 2188.7; qualifying community-apartment-project conversions to condominiums; and qualifying stock-cooperative conversions to condominiums.
    • For a minor subdivision, the County page states that the project may create no more than four parcels, four condominiums, or four community-apartment-project parcels, or convert a dwelling to a stock cooperative containing no more than four dwelling units; seven copies of the tentative map are required.
    • The County's minor-subdivision process states that an early-assistance meeting is required before a Development Footprint Analysis application; a Development Footprint Analysis is required before a parcel or tentative map for subdivisions not eligible under SB 9 and not subject to a Master Land Division Plan requirement.
    • The County reviews conformity with the General Plan, Zoning Ordinance, and other regulations; applicable environmental review, agency review, public notification, and public-hearing requirements may apply.
    • The County page lists an approximate processing time of 6–8 months and approximate fee of $14,600, but states that time and fees vary with project complexity and location and may be higher or lower.
    • The County page states that public notice is mailed to property owners within a 300-foot radius and that most permit decisions may be appealed within 10 business days.
    • The October 8, 2024 adopting ordinance recodifying subdivision regulations states that it takes effect 30 days after California Coastal Commission certification; the County's ordinance-code page states that the ordinance remains under Coastal Commission review and is not yet effective in the coastal zone. No October 8, 2024 effective date is assigned here.

    minor subdivision maximum parcels: <= 4 parcels (The County definition also covers up to four condominiums, up to four community-apartment-project parcels, or conversion to a stock cooperative containing up to four dwelling units.) · minor subdivision tentative-map copies: 7 copies · minor subdivision approximate processing time: 6-8 months (Approximate only; excludes appeals and may vary by project complexity and location.) · minor subdivision approximate fee: 14600 USD (Approximate rounded total; actual fees may vary and additional department fees may apply.) · public-notice radius: 300 feet · appeal period: 10 business days (Applies to most permit decisions; decision-maker and appeal route vary.)

    “The requirements set forth in the Subdivision Regulations apply to all or parts of subdivisions within the unincorporated territory of the County of San Mateo. Every person, firm, corporation, partnership, or association seeking to subdivide land within the unincorporated territory of San Mateo County will be subject to the provisions of these Subdivision Regulations, except as provided in Section 7003, below.”
  • Driveway accessRequired

    Replacing or constructing a new driveway within the right-of-way of San Mateo County unincorporated districts.

    • An encroachment permit from the San Mateo County Department of Public Works is required.
    • Replacing an existing driveway to the same grade and dimensions has a listed fee of $146.
    • A new driveway, or widening or regrading an existing driveway, has a listed fee of $762.

    existing driveway remove and replace to same grade and dimensions: 146 USD · new driveway or widening and/or regrading existing driveway: 762 USD

    “Replacing or constructing a new driveway within the right-of-way of San Mateo County's unincorporated districts requires an encroachment permit from the Department of Public Works.”
  • Building in a floodplainRequired

    Development in FEMA-designated flood zones and construction or other development within floodplains in unincorporated San Mateo County.

    • Applicants in all FEMA-designated flood zones except Moderate to Low Risk Areas designated Zone X must demonstrate compliance with development standards.
    • Habitable and utility areas must be at least one foot above the base flood elevation.
    • Areas below the base flood elevation are limited to garage and/or crawlspace purposes constructed according to currently adopted and enforced building regulations.
    • New construction must be anchored against movement by floodwaters, resistant to flood forces, constructed with flood-resistant materials, and flood-proofed or elevated so that the first floor of living space and all mechanical and services are at least one foot above the elevation of the 100-year flood.
    • These standards apply to new structures and substantial improvements of existing structures.
    • Most other types of development within the floodplain, including grading, cut and fill, riprap, and bank stabilization, also require a floodplain development permit.
    • The County defines substantial improvement as reconstruction, rehabilitation, or an addition whose cost exceeds 50% of the structure's value, using $300.00 per square foot as replacement cost.

    minimum elevation above base flood elevation: >= 1 foot · substantial improvement threshold: > 50 percent of structure value (Replacement cost uses $300.00 per square foot) · Zone X exception: Zone X (Moderate to Low Risk Areas designated Zone X are excepted from the NFIP compliance process described)

    “Additionally, most other types of development within the floodplain also require a floodplain development permit, such as grading, cut and fill”
  • Short-term rentalsLimited

    Short-term rentals of legal residences on parcels zoned Single Family (R-1) or Multi-Family (R-3) within the unincorporated San Mateo County Coastal Zone.

    • A valid short-term rental permit is required for each property address.
    • The rental must be in the Coastal Zone and in a legal residence on a parcel zoned R-1 or R-3.
    • Transient Occupancy Tax must be paid for each night rented, and proof of a County Transient Occupancy Registration Certificate or satisfactory alternative evidence is required with the application.
    • Short-term rentals may not use an accessory dwelling unit, may not be rented more than 180 nights per calendar year, and nights when the owner is present do not count toward that limit.
    • Maximum occupancy is two persons per rented bedroom plus two additional persons; children under 12 are excluded from the maximum.
    • At least one on-site parking space is required, or two spaces when maximum occupancy exceeds eight tenants; multifamily units require at least one on-site space.
    • A local contact person must remain within 20 miles, be available at all times while occupied, and be able to physically respond within no more than one hour in an emergency.
    • The application requires, among other items, a completed application, rental agreement or advertisement stating performance standards, parking evidence, visible street number, liability insurance proof, and applicable department fees.
    • The Community Development Director approves applications only if all requirements are met and the owner has no outstanding County compliance-related violations. Public notice must be given at least 10 calendar days before the decision; a hearing is not required and the decision is not appealable to the Planning Commission or Board of Supervisors.
    • The permit automatically expires three years after issuance or when the permit holder no longer owns or leases the rental, whichever occurs first; renewal may be requested up to six months before expiration.
    • The County webpage lists an estimated processing time of 3-4 weeks and an estimated fee of $500; these are rounded estimates and may vary, and additional permits, fees, and reviews may apply.

    short-term rental duration: < less than 30 days (Excludes ongoing month-to-month tenancy to the same renter and rent-free house exchanges.) · annual rental limit: <= 180 nights per calendar year (Owner-present nights do not count.) · maximum occupancy: 2 persons per bedroom plus 2 persons (Children under 12 are not counted.) · local contact radius: <= 20 miles (Contact must be available while occupied and respond physically within one hour in emergencies.) · estimated processing time: 3-4 weeks (Approximate estimate only; does not include appeals or non-Planning permits.) · estimated permit fee: 500 USD (Approximate rounded estimate; actual fees may vary and additional department fees may apply.)

    “In the Coastal Zone, Short-Term Rentals, subject to a short-term rental permit issued in accordance with County Zoning Regulations, Chapter 22, Section 6401.3.”
  • Permit feesPublished

    Building permit and development-related fees administered by San Mateo County for unincorporated areas.

    • The Building Service Fee Schedule is identified as effective April 1, 2026.
    • Affordable Housing Impact Fees apply only to residential and non-residential development of certain types and sizes.
    • Projects up to and including 3,500 square feet of net new gross floor area are exempt from the Affordable Housing Impact Fee; projects over 3,500 square feet pay the fee on the total net new gross floor area.
    • The source states that various exemptions, waivers, and modifications may apply.

    fee schedule effective date: 2026-04-01 · single-family detached home, 1 unit housing impact fee for first 2,500 square feet: 0 USD per square foot ($5.00 per square foot over 2,500 square feet) · single-family detached home, 2 to 4 units housing impact fee for first 2,500 square feet: 5 USD per square foot ($12.50 per square foot over 2,500 square feet) · single-family detached home, 5 or more units housing impact fee: 15 USD per square foot · non-residential projects exempt threshold: <= 3500 square feet of net new gross floor area (Projects generating in excess of 3,500 square feet pay on the total net new gross floor area)

    “Building Service Fee Schedule Fee Schedule (effective April 1, 2026)”
  • Permit processPublished

    Published planning-permit and building-permit process for projects in unincorporated San Mateo County.

    • The County states that procedural requirements vary under state law and County ordinances and that each permit type may have different processing requirements.
    • If both planning and building permits are needed, the planning permit must be obtained before applying for the building permit; an approved planning permit does not authorize construction without a building permit.
    • Planning permits are required when a project requires relief from the zoning ordinance or when the zoning ordinance mandates a permit for the proposed use or development; Design Review, Coastal Zone, Resource Management, Planned Agriculture, and hazard-overlay districts always require planning review first.
    • Planning-permit applications may be submitted by email or in person; short-term-rental planning permits are accepted online.
    • Planning applications are generally reviewed for completeness within 30 days; building applications generally within 5 days. After completeness and payment of initial fees, the review clock begins.
    • Plan-check agencies generally must complete reviews or provide comments within 30 days of receiving the application.
    • The County identifies a Planning Service Fee Schedule and Building Service Fee Schedule effective April 1, 2026.
    • Building-permit exemptions must be checked in pages 12-18 of the County Building Ordinance.
    • Additional permits or reviews may be required from Public Works, Environmental Health Services, Caltrans, utility providers, Building, Fire, Civil/Drainage, or Geotechnical reviewers.

    planning application completeness review: generally 30 days (Actual timing varies by project and permit type.) · building application completeness review: generally 5 days (Actual timing varies by project and permit type.) · plan-check review: generally 30 days (Agencies may provide comments for resubmittal.) · fee schedule effective date: April 1, 2026 (Planning and building fee schedules are separate.)

    “The Planning and Building Department issues permits for a wide range of planning and building projects in unincorporated San Mateo County. Because of varying procedural requirements in State law and County ordinances, each type of permit may be subject to different processing requirements. We process each permit as quickly as possible while ensuring full compliance with the law. The general process for planning permits and building permits is summarized below.”

California rules that apply here

  • Owner-builder exemptionAvailable (with conditions)

    Exemption from California contractor-licensing chapter for an owner-builder who builds or improves a structure on the owner’s property; this does not itself establish exemption from local building permits, inspections, or other code requirements.

    • For work personally performed by the owner or performed by the owner’s employees, none of the improvements may be intended or offered for sale, and employee compensation must be wages as their sole compensation.
    • For work directly contracted to licensed trade contractors, the owner must directly contract with licensees duly licensed for the respective trades.
    • For single-family residential structures under the licensed-contractor arrangement, no more than four structures may be intended or offered for sale in a calendar year; this limitation does not apply if the owner contracts with a general contractor for construction.
    • For a homeowner improving a principal residence or its appurtenances, the work must be performed before sale, the homeowner must have actually resided in the residence for the 12 months before completion, and the homeowner must not have used this exemption on more than two structures more than once during any three-year period.
    • A nonprofit corporation may qualify when assisting an owner-builder participating in a mutual self-help housing program.
    • Sale or offering for sale within one year after completion creates a rebuttable presumption that the structure was undertaken for sale; sale or offering for sale of five or more structures within one year creates a conclusive presumption.
    • This is a contractor-licensing exemption and should not be treated as a building-permit exemption.

    single-family structures intended or offered for sale: <= 4 structures per calendar year (Does not apply if the owner contracts with a general contractor for construction.) · prior residence occupancy: >= 12 months before completion (Applies to the principal-residence homeowner exemption.) · owner-builder exemption use: <= 2 structures during any three-year period (The statute states the homeowner has not availed himself or herself of the exemption on more than two structures more than once during any three-year period.) · sale presumption period: 1 year after completion (Sale or offering for sale creates a rebuttable presumption; five or more structures creates a conclusive presumption.) · conclusive-presumption threshold: >= 5 structures within one year after completion (Structures sold or offered for sale by the owner-builder.)

    “This chapter does not apply to any of the following: (1) An owner who builds or improves a structure on his or her property”
    3 more reviewed findings on this topic
    • Conditional — California Contractors State License Law exemption for qualifying owner-builders, including qualifying projects in San Mateo County.
      “An owner-builder is exempt from licensure, but there are limitations.”
    • Conditional — Owners who build or improve structures on their own property, and homeowners improving their principal residence or appurtenances, subject to Business and Professions Code section 7044.
      “(a) This chapter does not apply to any of the following: (1) An owner who builds or improves a structure on his or her property”
    • Available (with conditions) — California contractor-licensing requirements for an owner who builds or improves a structure on the owner’s property; this is not stated as an exemption from building permits, inspections, or other code requirements.
      “This chapter does not apply to any of the following: (1) An owner who builds or improves a structure on his or her property”
  • Building code adoptedAdopted (with conditions)

    California Building Standards Code, California Code of Regulations, Title 24, including the 2025 California Building Code and related parts, for buildings and structures subject to the state code.

    • The 2025 California Building Standards Code applies to buildings and structures with a permit application date on or after January 1, 2026.
    • The applicable local building department or enforcing agency determines how the permit application date is established in a specific jurisdiction.
    • The code includes multiple parts, including the California Building Code, California Residential Code, Existing Building Code, Electrical Code, Mechanical Code, Plumbing Code, Energy Code, Wildland-Urban Interface Code, Fire Code, and Green Building Standards Code.

    effective date: 2026-01-01 · permit application date: >= 2026-01-01

    “The 2025 California Building Standards Code (CBSC), California Code of Regulations (CCR), title 24, will become effective on January 1, 2026, as a result of the 2024 Triennial Code Adoption Cycle. [...] The 2025 CBSC applies to all buildings and structures with a permit application date on or after January 1, 2026.”
    One more reviewed finding on this topic
    • Adopted — California statewide building standards, including residential construction subject to Title 24 of the California Code of Regulations.
      “Except as otherwise specifically provided by law, the building standards adopted and submitted by the department for approval [...] shall be adopted by reference”
  • Manufactured homesAllowed (with conditions)

    Occupancy of manufactured homes inside or outside mobilehome parks in California.

    • The manufactured home must satisfy applicable federal standards and California Manufactured Housing Act and Title 25 requirements.
    • Installation and approval for occupancy are governed by the Mobilehome Parks Act.
    • HCD or a local enforcement agency with assumed Mobilehome Parks Act authority is responsible for ensuring compliance with statutory construction and maintenance requirements.
    • Local agency approvals may be necessary for the project.

    minimum width for a new manufactured home: >= 8 body feet (The statutory definition also includes units at least 40 body feet in length.) · minimum erected floor area for a new manufactured home: >= 320 square feet

    “MHs may be occupied outside or inside of mobilehome parks and installation and approval for occupancy is governed by the Mobilehome Parks Act (MPA), HSC Sections 18200, et seq., and Title 25, CCR Sections 1000, et seq.”
  • Accessory dwellingsAllowed (with conditions)

    ADUs and junior ADUs subject to California State ADU Law.

    • Approval is ministerial and without discretionary review or a hearing.
    • Development standards must be objective and knowable in advance.
    • The local permitting agency must determine application completeness and provide written notice within 15 business days.
    • If an application is incomplete, the agency must identify missing items and explain how to complete it.
    • Local site, building, health, safety, fire, utility, and other applicable requirements continue to apply.

    written completeness determination: <= 15 business days (Measured from the permitting agency's receipt of the application.) · final written determination after appeal: <= 60 business days (Applies after receipt of the written appeal.)

    “A permit application for an accessory dwelling unit shall be considered and approved ministerially without discretionary review or a hearing [...] A permitting agency shall determine whether an application to create or serve an accessory dwelling unit is complete and provide written notice of this determination to the applicant not later than 15 business days after the permitting agency received the application.”
  • Campground & park staysLimited

    Occupancy and use of manufactured homes and mobilehomes in California mobilehome parks and other locations subject to HCD jurisdiction.

    • HCD administers titling and registration for manufactured homes and mobilehomes.
    • HCD-inspected mobilehome parks are subject to health and safety enforcement where local government has not assumed enforcement.
    • Manufactured/mobilehome park regulations address construction, use, maintenance, and occupancy.
    • Separate local land-use, building, fire, health, and utility requirements may apply.
    “MHs may be occupied outside or inside of mobilehome parks and installation and approval for occupancy is governed by the Mobilehome Parks Act (MPA), HSC Sections 18200, et seq., and Title 25, CCR Sections 1000, et seq.”
    One more reviewed finding on this topic
    • Limited — Occupancy and use of recreational vehicles in California special occupancy parks and designated RV sections of mobilehome parks.
      “Unless otherwise allowed by a local ordinance, RVs generally may be occupied only in mobilehome parks or special occupancy parks governed by the Mobilehome Parks Act”
  • county zoning authorityGeneral

    California county legislative bodies' authority to adopt zoning ordinances regulating buildings, structures, land uses, lots, yards, open space, lot coverage, intensity of use, parking, loading, and setbacks within county jurisdiction, including unincorporated areas.

    • The authority is exercised pursuant to Government Code Chapter 4, Zoning Regulations.
    • The statute separately authorizes city legislative bodies; incorporated municipalities may exercise their own zoning authority.
    • Government Code Section 65850 also lists authority to regulate signs and billboards, building and structure location, height, bulk, number of stories, and size, lot and open-space size and use, lot coverage, intensity of land use, offstreet parking and loading, and building setback lines.
    • The cited section states it was amended by Stats. 2017, Ch. 376, Sec. 1, effective January 1, 2018.
    “The legislative body of any county or city may, pursuant to this chapter, adopt ordinances that do any of the following:”
  • county building authorityGeneral

    California counties administering and enforcing state building standards through county building departments, including residential construction in unincorporated areas.

    • Each county must maintain building standards and state building regulations in the office of the building official responsible for administration and enforcement of state building standards.
    • The statewide Title 24 standards apply subject to statutory exceptions and any authorized local amendments or local requirements.
    • The cited HCD bulletin concerns the 2019 California Building Standards Code and its July 1, 2021 supplement; later code editions may supersede those particular edition dates.
    “These codes shall be maintained in the office of the building official responsible for the administration and enforcement of state building standards”

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.

Living off-grid in San Mateo County, California

Is San Mateo County a good place to live off-grid or homestead?

San Mateo County scores 35/100 on the Bolthole Index, a marginal county profile. Its strengths: workable self-sufficiency basics (28.7″/yr rainfall). Watch-outs: about 722,806 people within 15 miles and elevated current hazard exposure.

Do you need a building permit in San Mateo County, California?

San Mateo County generally requires a residential building permit, and it enforces county zoning. Onsite septic is permitted by San Mateo County Environmental Health Services. Owner-builders may act as their own contractor to build their home. These answers are quoted from official sources and independently re-checked. Rules change and cities within the county differ — always confirm with the county before you buy or build.

Can you live in an RV or tiny home on your land in San Mateo County?

Living in an RV on your own land in San Mateo County is allowed on a temporary basis only: Statewide rule. Occupancy of recreational vehicles as residential units in California. RVs are not intended for occupancy as permanent dwellings. Unless a local ordinance allows otherwise, RV occupancy generally is limited to mobilehome parks or special occupancy parks governed by the Mobilehome Parks Act or Special Occupancy Parks Act. A tiny home is limited to specific cases. Confirm with the county before relying on it.

How much does land cost in San Mateo County, California?

Land in San Mateo County runs about $12,311 per acre, based on the latest county data.

What is the water situation in San Mateo County?

San Mateo County gets about 28.7" of rain a year, with severe drought in roughly 31.9% of years.

How remote is San Mateo County?

A typical private-land location has about 722,806 people within 15 miles and 9,988,219 within 100 miles. These radius catchments are the published fallback where road routing is unavailable.

How San Mateo compares in California

Compare side-by-side →See all 58 California counties ranked →