Zoning, building permits and septic rules in Arco, Idaho

Arco’s own rules

• Building permitRequired

  Erecting, constructing, enlarging, altering, repairing or moving a building or structure inside Arco city limits.

  • Exemptions under 15.08.030: re-roofing; storage sheds of less than 250 sq. feet; signs (as permitted by code); other cases determined by the building official or city council. Electrical and plumbing permits may still be required.
  • 15.08.020: construction plans must be prepared by an Idaho licensed engineer or architect, except dwellings and lodging houses of two stories or less and private garages, carports and sheds (those are plan-checked by the building official).
  • 15.08.040 provides a separate building permit path for single-purpose agricultural buildings (plot plan and application approved by the building official).

  storage shed exemption threshold (no building permit below this area): < 250 sq ft (electrical and plumbing permits may still be required)

  “no building permit is required (electrical and plumbing permits may still be required) for: 1. re-roofing; 2. storage sheds of less than 250 sq. feet;”

• Building code adoptedAdopted (with conditions)

  Erection, construction, alteration, occupancy and maintenance of buildings and structures inside Arco city limits.

  • Adopts International Building Code, International Residential Code (parts I to IV and IX) and International Energy Conservation Code, with the exclusion of 'building permit fees'.
  • Chapter 15.04 also adopts the 1997 Uniform Plumbing Code, the current National Electric Code, the 1997 Uniform Mechanical Code, the 1997 Uniform Fire Code and the 1997 Uniform Code for the Abatement of Dangerous Buildings; copies are on file with the city clerk.
  • Agricultural buildings are exempt from the adopted building codes but remain subject to zoning placement requirements (15.04.010).

  “international building code; • international residential code, parts i to iv and ix; • international energy conservation code; - published by the international code council, referenced herein, be and the same are hereby adopted (with the exclusion of "building permit fees")”

• Local zoningPresent (with conditions)

  All land inside Arco city limits: the city administers its own zoning ordinance (Title 17, Zoning).

  • Title 17 is the city's own zoning code, adopted by the city council; the 12May2025 / Ordinance 2025-C stamp on the chapters is a code revision stamp, not an effective date.
  • Zoning map and districts are in Chapter 17.08.

  “this title shall be known as the "zoning title of the city of arco."”

• Zoning districtsPublished (with conditions)

  Zoning districts for land inside Arco city limits.

  • Districts named in 17.08.030: A agricultural; AT agricultural-transitional; R-1 residence; R-2 residence (multi-family); R-3 residence (5+ multi-family); C commercial; I industrial; P public; area of city impact.
  • The extracted text of the district list is garbled in the PDF, so verify district names against the official zoning map before relying on them.
  • Chapter 17.42 Public Zone appears on the city index only as a draft (filename 'Public Zone Draft v1'); not opened.

  “for the purpose of this title the city shall be and is divided into zoning districts as follows:”

• Minimum lot sizeSpecified

  R-1 residence zone inside Arco city limits.

  • Lot width of not less than sixty feet at the established building line.
  • Corner lots keep the interior side yard rule, except a ten-foot side yard on the street side (17.28.080 b).

  minimum lot area: >= 7000 sq ft

  “residential r-1 lots shall have an area of not less than seven thousand square feet and a width at the established building line of not less than sixty feet;”

  One more reviewed finding on this topic

  • Specified — A agricultural zone inside Arco city limits, including the single-family dwelling permitted there.

    “the minimum lot area shall be forty (40) acres.”

• SetbacksSpecified

  R-1 residence zone inside Arco city limits.

  • Accessory buildings may not encroach on the front yard; they may encroach on the side yard but no building may be closer than ten feet to a lot line.
  • Corner lots: side yard adjacent to the street is ten feet (17.28.080 b).

  front yard minimum: >= 25 ft · side yard minimum: >= 10 ft · rear yard minimum: >= 25 ft · accessory building minimum distance to lot lines: >= 10 ft

  “front yards in the residential r-1 zone shall be a minimum of twenty-five feet.”

  One more reviewed finding on this topic

  • Specified — A agricultural zone inside Arco city limits.

    “no building shall be erected closer than twenty (20) feet to any side property line, except corner lots shall maintain a thirty (30) foot side yard adjacent to the street”

• Building heightSpecified

  R-1 residence zone inside Arco city limits.

  • Height limit is measured from ground level.

  maximum building height: <= 35 ft (also limited to two and one-half stories) · maximum building stories: <= 2.5 stories (also limited to 35 feet)

  “buildings shall not be erected or enlarged to exceed a height of two and one-half stories or thirtyfive feet in height from ground level.”

  One more reviewed finding on this topic

  • None — A agricultural zone inside Arco city limits.

    “there shall be no height restrictions in the agricultural zone.”

• Accessory dwellingsLimited

  Second dwelling units inside the R-1 residence zone in Arco city.

  • Second dwelling on a lot is allowed only by conditional use permit under 17.28.085.
  • A two-story garage with living quarters upstairs may be occupied by a family member of the main-structure occupants.
  • A guest house without kitchen, or guest rooms in an accessory building, is allowed only for occasional guests, not permanent occupancy by others.
  • Conditional use is granted by the planning commission after notice and public hearing (17.28.015).

  “no residential structure shall be erected upon the rear of a lot or upon a lot with another dwelling, execpt by conditional use permit”

  One more reviewed finding on this topic

  • Limited — Additional dwellings in the A agricultural zone inside Arco city.

    “m. additional dwellings on the property for farm related purposes”

• Mandatory utility hookupSewer (with conditions)

  Residence, business or premises inside Arco city limits that is approved for occupancy and occupied or used.

  • The section sets no distance-to-main or availability test; the duty applies to premises within city boundaries that are approved for occupancy and occupied or used.
  • Connection must be made within 120 days after official written notice from the city, which must cite the chapter language.
  • Other chapter 13.04 sections (permits and fees, side sewer, grease traps, rates) were not opened.

  connection deadline after official written notice: 120 days

  “every residence, business or premises within the boundaries of the city of arco, approved for occupancy and occupied or used by any person or persons, or as a commercial business, shall be connected to the public sanitary sewer system.”

• Agricultural exemptionConditional

  Agricultural buildings inside Arco city limits, limited to the adopted building codes.

  • Exemption is from the adopted building codes only, not from zoning placement requirements.
  • 15.08.040 gives a permit path for single-purpose agricultural buildings (plot plan and application approved by the building official).

  “agricultural buildings are exempt from the building codes adopted herein but shall remain subject to placement requirements established by zoning regulations.”

• Permit processPartial

  Building permit issuance for construction inside Arco city limits.

  • Permit issuance requires building official review and approval of plans and application, and payment of the fees.
  • Plans must be prepared by an Idaho licensed engineer or architect, except as listed in 15.08.020 c.
  • Zoning review, public hearing and appeal steps were not located in the opened text.

  “building permits may be issued after: a. the construction plans and application have been reviewed and approved by the building official;”

Still unanswered

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

• Owner-builder exemption — Owner-builder exemption for a homeowner building their own house inside Arco city limits.
• Inspections — Building inspections for construction inside Arco city limits.
• Certificate of occupancy — Certificate of occupancy for new homes inside Arco city limits.
• Minimum dwelling size — Minimum floor area of a dwelling inside Arco city limits.
• Lot coverage — Maximum lot coverage in Arco city residential districts.

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.