Bolthole Index

Washington County, Idaho

Building permits, zoning and land rules in Cambridge, Idaho

Cambridge, Idaho requires city building permits for new construction and remodeling, subject to limited exceptions.1 Cambridge sets its own zoning; use the city rules for property inside city limits in Washington County.2 Cambridge requires public sewer connection when the sewer is within 250 feet of the property line; eligible septic systems instead need a health-district permit from Southwest District Health.345

At a glance

Building permits
City building permits required, with limited repair and temporary accessory-structure exceptions1
Zoning
Cambridge zoning applies to the city and its designated impact area2
Wastewater
Public sewer connection required within 250 feet of the property line; eligible septic systems need a health-district permit34
RV living
Temporary use permit for up to 180 days per calendar year; active water, wastewater and electrical services required on vacant lots6
Accessory dwelling
Conditional in single-family residential zones; maximum size is the lesser of 800 square feet or 75% of the principal dwelling7
Lot size
R-zone lot minimums depend on utilities and lot type; obtain the city’s parcel-specific determination8
Private wells
Idaho drilling permit and licensed well driller required before drilling9

Who to call

Building permits

Cambridge City Clerk / Building Official

Start here for Cambridge city building applications and referral to zoning and floodplain review

Septic permits

Southwest District Health — Septic & Land Development

Septic-tank and drainfield permits and property site evaluations

208-455-5400

Online permits →

Contact details are copied from each office’s official page and were checked against it on October 12, 2026.

Off-grid gear

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

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Do you need a building permit in Cambridge, ID?

Cambridge requires a city building permit for structures regardless of size, including new construction, remodeling and fences over 6 feet high.1 Maintenance or repair without structural modification is excepted.1 A detached temporary accessory structure used as a tool shed, storage shed, playhouse or similar use can qualify for an exception when it is single-story, has no foundation and is no larger than 200 square feet.1 Cambridge’s temporary structures still must meet zoning and setback requirements, so a building-permit exception does not remove the land-use review.1

Who issues building permits in Cambridge, and where do you start?

Cambridge issues city building permits, and required zone changes, conditional use permits and variances must be approved before the building permit is issued.10 Start with the City Clerk’s building application and ask for the current application checklist, fee schedule and building-official contact.11 Cambridge collects building-permit fees before issuance.10 Idaho also requires electrical, plumbing and HVAC permits, with administration depending on the local jurisdiction; ask which trade permits must be obtained separately for your Cambridge project.12 Septic review belongs with Southwest District Health rather than the city building application.5

Does Cambridge have zoning, and what lot size can you build on?

Cambridge has zoning covering the city and its designated impact area.2 In Cambridge’s R residential zone, the general principal-dwelling minimum is 40,000 square feet, but the code allows reductions where municipal water and/or public water and sewer are available, subject to city regulations.8 The R-zone provision also states minimum areas of 8,000 square feet for corner lots and 7,560 square feet for inside lots under its utility-served provisions.8 Ask the City Clerk for the applicable district, utility status and written lot-size determination before choosing a house plan.8 We could not confirm the numeric residential setbacks or a general minimum dwelling floor area; request those standards from the city with the lot-size determination.

How do sewer connections and septic permits work in Cambridge?

Cambridge requires sewer connection for occupied or commercially used parcels when public sewer is within 250 feet of the property line.3 Cambridge cannot issue a building permit for construction within that threshold unless the plans show a sewer connection.3 An existing unconnected property must connect within 60 days after official city notice.3 Where an individual septic system is eligible, the property owner needs a public health district permit before installation.4 Southwest District Health handles septic tanks and drainfields and requires an on-site property evaluation before issuing a subsurface sewage disposal permit.5 Confirm the sewer obligation with Cambridge before paying for septic design; then coordinate the evaluation and installation inspection with Southwest District Health.3513

Can you live in an RV or tiny home in Cambridge?

Cambridge allows a temporary use permit for a licensed RV on a single-ownership parcel for up to 180 days per calendar year, issued by the City Clerk to the property owner.6 Friends, relatives and bona fide visitors staying no longer than 2 weeks do not need that permit.6 An occupied RV cannot be placed on a vacant Cambridge lot without water, wastewater and electrical services in an active status.6 We could not confirm a separate Cambridge tiny-home occupancy rule; ask the city how the proposed structure will be classified. Cambridge conditionally allows an ADU in single-family residential zones, limited to the lesser of 800 square feet or 75% of the principal dwelling, with separate water, sewer and power connections.7

Building a home in Cambridge: what are the steps in order?

  1. Ask Cambridge to establish the parcel’s zoning district and applicable utility-dependent lot standards, and resolve any needed zone change, conditional use permit or variance before building-permit issuance.810
  2. Confirm sewer availability with Cambridge; if septic is eligible, arrange Southwest District Health’s site evaluation and septic permit.345
  3. For construction or development in a special flood hazard area, obtain Cambridge’s floodplain development permit before work begins, including fill or manufactured-home placement.14
  4. Submit the city building application, pay the required fees before issuance and establish who administers the electrical, plumbing and HVAC permits.1012
  5. Request the city’s inspection schedule and occupancy sign-off requirements before scheduling construction; we could not confirm those Cambridge procedures.

What should you check before buying land in Cambridge?

Cambridge’s subdivision rules allow an original parcel to be divided into no more than 2 lots when each meets zoning standards; subsequent divisions require subdivision plat approval.15 The agricultural division exception is for parcels of at least 5 acres used solely for agriculture without new street dedication other than widening existing streets; it does not establish a residential building exception.16 Idaho requires an IDWR drilling permit before drilling a private well and a licensed well driller, even where a domestic water-right permit exemption applies.9 A driveway connecting to a state highway needs an ITD encroachment permit.17 For land outside Cambridge, consult the Washington County guide for the county building-permit answer, while also checking whether Cambridge’s designated impact-area zoning applies.182

Watch-outs

  • A Cambridge RV temporary use permit is limited to 180 days per calendar year and does not authorize indefinite occupancy.6
  • Nearby public sewer can make a septic plan unsuitable: Cambridge requires sewer connection within 250 feet of the property line.3
  • A Cambridge floodplain development permit covers development such as fill as well as structures in special flood hazard areas.14
  • We could not confirm Cambridge’s general inspection schedule, occupancy sign-off procedures or numeric residential setbacks; ask the City Clerk to obtain the building official’s requirements.11

Sources

  1. 9-1-2: Building Permits Required (Cambridge), quoted and re-checked
  2. codelibrary.amlegal.com (Cambridge), quoted and re-checked
  3. 8-2-1: Sanitary Sewer System; Mandatory Connection (Cambridge), quoted and re-checked
  4. Septic and Septage (Cambridge), quoted and re-checked
  5. Southwest District Health — Septic & Land Development (swdh.id.gov)
  6. 9-3-3: Permits Required (Cambridge), quoted and re-checked
  7. 10-4-2: R Residential Zone (Cambridge), quoted and re-checked
  8. 10-4-2: R Residential Zone (Cambridge), quoted and re-checked
  9. Wells Overview (Idaho statewide rule), quoted and re-checked
  10. 9-1-2: Building Permits Required (Cambridge), quoted and re-checked
  11. Cambridge City Clerk / Building Official (cambridge.id.gov)
  12. Frequently Asked Questions (FAQs) - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
  13. IDAPA 58.01.03 Individual/Subsurface Sewage Disposal Rules (Idaho statewide rule), quoted and re-checked
  14. 12-1-6-1: Development Permit (Cambridge), quoted and re-checked
  15. codelibrary.amlegal.com (Cambridge), quoted and re-checked
  16. codelibrary.amlegal.com (Cambridge), quoted and re-checked
  17. Types of Right-of-Way Encroachment Permits (Idaho statewide rule), quoted and re-checked
  18. Washington County Code, Chapter 1 Building Codes (2026 county census)

Written October 12, 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 Cambridge

Cambridge’s own rules

  • Building permitRequired

    All structures inside Cambridge city, including new construction, remodeling, and fences over six feet.

    • Maintenance or repair without structural modification is excepted.
    • One-story temporary detached accessory structures used as tool/storage sheds, playhouses, or similar uses are excepted if no more than 200 square feet and without a foundation.
    • Temporary structures must meet zoning and setback requirements.
    • Zone changes, conditional use permits, and variances must be approved before a building permit is issued.

    temporary accessory structure maximum floor area: <= 200 square feet (One-story temporary detached accessory structures without a foundation)

    “The city requires building permits for any and all structures regardless of size or square footage, including all new construction, remodeling, and fences over six feet (6') in height.”
  • Building code adoptedAdopted

    Building construction inside Cambridge city.

    • The ordinance adopts the listed nationally recognized codes and states that the latest versions are adopted as amended, changed, or superseded.
    “Codes Adopted: The following nationally recognized codes are hereby adopted for the city:”
  • Local zoningPresent

    Cambridge city and its designated impact area.

    • The zoning title applies to the city and its impact area designated by a map and description in section 10-2-2.
    “This title shall apply to the city and its impact area as designated by a map and description referred to in section 10-2-2 of this title.”
  • Minimum lot sizeSpecified

    R residential zone inside Cambridge city.

    • The R-zone introductory dimensions apply where public water or public water and sanitary sewer systems are available.
    • For a principal one-family dwelling, the general minimum is 40,000 square feet and 150 feet width per side, but the minimum may be reduced where municipal water and/or public water and sewer systems are available, subject to city regulations.
    • Corner lots must be at least 8,000 square feet and inside lots at least 7,560 square feet under the stated R-zone provision.

    R-zone minimum lot dimensions: 54 x 140 feet (Where public water or public water and sanitary sewer systems are available) · R-zone corner-lot minimum area: >= 8000 square feet · R-zone inside-lot minimum area: >= 7560 square feet · principal dwelling general minimum lot area: >= 40000 square feet (May be reduced where municipal water and/or public water and sewer systems are available)

    “No Principal Dwelling Unit shall be erected or building altered to accommodate one family as a residence on a lot having less than forty thousand (40,000) square feet of lot area and width of at least one hundred fifty feet (150') per side, except where municipal water and/or public water and sewer systems are available, then the minimum lot size may be reduced subject to any city regulations thereon.”
  • Living in an RVLimited

    Occupied recreational vehicles on private parcels inside Cambridge city.

    • One recreational vehicle may receive a temporary use permit for no more than 180 days in a calendar year.
    • The permit is issued by the City Clerk to the property owner and requires the RV to be licensed.
    • Without a permit, recreational vehicles may not be used as living quarters longer than two weeks.
    • No occupied RV may be placed on a vacant lot without water, wastewater, and electrical services in an on status.
    • Emergency permits may allow temporary living quarters for up to 180 days when a true emergency exists.

    temporary use permit duration: <= 180 days per calendar year (One recreational vehicle on a single-ownership parcel) · unpermitted occupancy duration: <= 2 weeks (Friends, relatives, and bona fide visitors)

    “Recreational vehicles are primarily designed as temporary living quarters for recreational, camping or travel use, and shall not be used for living quarters longer than two (2) weeks, except with a temporary use permit.”
  • Camping on your landLimited

    Temporary camping or occupancy by recreational vehicles inside Cambridge city.

    • Visitors may stay two weeks or less without a permit.
    • Longer occupancy requires a temporary use permit, generally capped at 180 days in a calendar year for one RV.
    • Emergency permits are available for qualifying emergencies for up to 180 days.
    “No permit shall be required of friends, relatives or bona fide visitors staying two (2) weeks or less.”
  • Accessory dwellingsAllowed (with conditions)

    Accessory dwelling units in Cambridge city's single-family residential zones.

    • Maximum one ADU per lot or parcel.
    • Must comply with residential building, health, safety, and fire codes.
    • Must meet zoning setback and height requirements.
    • ADU may not exceed 75% of the principal dwelling or 800 square feet, whichever is less.
    • No more than two bedrooms.
    • One off-street parking space per ADU.
    • Separate water, sewer, and power connections are required.
    • A temporary ADU may be installed with a conditional use permit.

    maximum ADUs: 1 per lot or parcel · maximum ADU size: <= 800 square feet (Also may not exceed 75% of principal dwelling size; lesser limit controls) · maximum ADU bedrooms: <= 2 bedrooms

    “The installation of an Accessory Dwelling Unit in new or existing single-family dwellings (hereinafter Principal Dwelling Units) may be allowed in single-family residential zones, subject to the specific standards listed below.”
  • Mandatory utility hookupSewer (with conditions)

    Every parcel inside Cambridge city improved for human occupancy, used by a person, or used as a commercial business, when the public sewer is within 250 feet of the property line.

    • Connection must be made within 60 days after official city notice for an existing unconnected property.
    • No building permit may issue for construction where a public sewer line or main is within 250 feet unless plans show the sewer connection.

    public sewer distance threshold: <= 250 feet from property line · connection deadline after official notice: 60 days (Existing unconnected property)

    “Every parcel of land or premises within the boundaries of the city which has been or which is improved for human occupancy or used by any person, or used as a commercial business, shall be connected to the city public sanitary sewerage system; provided that the sewerage system is within two hundred fifty feet (250') of the property line.”
  • Agricultural exemptionConditional

    Land divisions inside Cambridge city or its stated impact area.

    • The exemption applies to division into parcels of five acres or more designated solely for agricultural purposes.
    • The division may not involve a new street dedication other than dedications widening existing streets.

    minimum parcel size: >= 5 acres (Solely agricultural purpose)

    “A division of land into parcels of five (5) acres or more designated to be used solely for agricultural purposes, and which does not involve any new street dedication other than dedications widening existing streets.”
  • Subdividing landRegulated (with conditions)

    Subdivision of land inside Cambridge city corporate limits.

    • Subdivision regulations also apply to the city's impact area in Township 14 North, Range 3 West of the Boise Meridian, Sections 2, 3, 10, and 11.
    • One original lot or parcel may be divided into no more than two lots if each resulting parcel meets applicable zoning standards; subsequent divisions require subdivision plat approval.
    • Divisions into parcels of five acres or more solely for agricultural purposes may be exempt if no new street dedication is involved other than widening existing streets.

    agricultural division minimum parcel size: >= 5 acres (Solely agricultural use and no new street dedication other than widening existing streets) · single split maximum resulting lots: <= 2 lots or parcels (One division of an original lot or parcel)

    “The regulations of this title shall apply to the subdividing of all land within the corporate limits of the city and its impact area being all land lying in Township 14 North, Range 3 west of the Boise Meridian, in Sections 2, 3, 10 and 11:”
  • Building in a floodplainRequired

    Construction or development within an area of special flood hazard inside Cambridge city.

    • A development permit is required before construction or development begins.
    • The requirement covers all structures, including manufactured homes, and all development including fill and other activities.
    • Applications may require scaled plans, elevations, floodproofing certification, and watercourse-alteration information.
    “A development permit shall be obtained before construction or development begins within any area of special flood hazard established in section 12-1-5 of this chapter.”
  • Permit processPartial

    Building-permit process inside Cambridge city.

    • A building permit is required for structures regardless of size, subject to listed exceptions.
    • Zone changes, conditional use permits, and variances must be approved before a building permit is issued.
    • Fees are collected before issuance.
    • The located code does not provide a complete application checklist or review timeline.
    “The city shall approve all zone changes, conditional use permits, and variances before a building permit is issued.”

Rules another office applies inside Cambridge

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

  • Septic permitRequired

    Installation of an individual septic system serving property inside Cambridge city when public sewer is unavailable or not required by the city.

    • The property owner must obtain a permit from the public health district before installing an individual septic system.
    • The city requires connection to public sanitary sewer when the sewer is within 250 feet of the property line.
    “To have a septic system installed, the property owner must obtain a permit from a public health district.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Cambridge or Washington County directly.

  • Owner-builder exemption — Owner-builders performing construction inside Cambridge city.
  • Inspections — Building inspections inside Cambridge city.
  • Certificate of occupancy — Certificates of occupancy for buildings inside Cambridge city.
  • Minimum dwelling size — Minimum dwelling size in Cambridge city's R residential zone.
  • Setbacks — Residential setbacks inside Cambridge city.
6 more unanswered
  • Lot coverage
  • Building height
  • Tiny homes
  • Well permit
  • 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 Cambridge publishes no rule on the point, not that none exists. Washington County’s page lists the county offices to call.

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