Zoning, building permits and septic rules in SeaTac, Washington

SeaTac’s own rules

• Building permitRequired

  Buildings, structures, and building-service equipment regulated by the technical codes inside SeaTac city limits.

  • Items specifically exempt in the applicable technical codes are excepted.
  • A separate appropriate permit must first be obtained from the Building Official.

  “Except for those items specifically exempt in each of the technical codes, no building, structure or building service equipment regulated by the technical codes shall be erected, constructed, enlarged, altered, repaired, moved, improved, removed, converted, or demolished unless a separate, appropriate permit for each building, structure or building service equipment has first been obtained from the Building Official.”

• Building code adoptedAdopted (with conditions)

  Residential construction inside SeaTac city limits.

  • The adopted IRC is amended by the Washington State Building Code Council and is subject to the local additions and exceptions stated in SMC § 13.110.030.

  “The most current edition of the International Residential Code, including Appendix F, Appendix Q and Appendix U, as amended by the Washington State Building Code Council and published in Chapter 51-51 WAC, is hereby adopted by reference as now or hereafter amended, with the following additions and exceptions:”

• InspectionsRequired

  Work regulated by SeaTac technical codes inside city limits.

  • The Building Official may accept written inspection reports from approved agencies or individuals.

  “Inspections. The Building Official shall make all of the required inspections, or the Building Official shall have the authority to accept reports of inspection by approved agencies or individuals.”

• Local zoningPresent (with conditions)

  Land and development inside SeaTac city limits.

  • Chapter 15.400 applies in all zones, including overlay districts and overlay zones.

  “In order to accomplish the purposes of the code, the following zone classifications and zoning map symbols are established:”

• Zoning districtsPublished (with conditions)

  Zoning districts inside SeaTac city limits.

  • The standards charts list general dimensional standards for each zone; additional standards in other code sections may also apply.

  “In order to accomplish the purposes of the code, the following zone classifications and zoning map symbols are established:”

• Accessory dwellingsLimited

  Accessory dwelling units in SeaTac residential zones.

  • ADUs count toward the maximum number of units per lot.
  • The chart limits units per lot by residential zone and increases may apply within one-quarter mile walking distance of a major transit stop.

  “MAXIMUM NUMBER OF UNITS PER LOT | 4 (1)(2) | 6 (1)(2) | 8 (1) | N/A | N/A | N/A | (1) Accessory dwelling units (ADUs) are included in maximum allowed number of units per lot.(2) May increase maximum number of units per lot by two (2) if within one-quarter (¼) mile walking distance of a major transit stop.”

• Permit feesPublished (with conditions)

  Construction permits inside SeaTac city limits.

  • A permit or revision cannot issue until all City fees are paid.
  • Fees are set by the most recently adopted City Fee Schedule.

  “A permit or permit revision shall not be issued until all fees owed to the City of SeaTac have been paid. The permit and plan review fees, together with other fees, shall be as set forth in the most recently adopted City of SeaTac Fee Schedule.”

• Permit processPublished (with conditions)

  Construction permits inside SeaTac city limits.

  • Application must include required information and City-specified construction documents.
  • Incomplete, inaccurate, or missing information prevents review.
  • Application fees are required for a complete application.

  “To obtain a permit for work regulated by this title, the applicant shall file an application for construction permit(s) with all required information, including an accurate description of the proposed scope of work. The application shall be accompanied by construction documents and information, as specified by the City, to include all data, reports, plans, specifications, calculations and any other information required to document compliance with applicable laws and regulations.”

Rules another office applies inside SeaTac

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

• Minimum lot sizeSpecified

  RL residential zone inside SeaTac city limits.

  • Lots may be less than the required minimum lot size subject to the criteria in SMC § 15.110.050, Lot Area.

  minimum lot area: 7200 square feet (Lots may be less than the required minimum lot size subject to SMC § 15.110.050.)

  “MINIMUM LOT AREA Lots may be less than the required minimum lot size, subject to the criteria in SMC § 15.110.050, Lot Area. | 7,200 SF | 7,200 SF | 7,200 SF (3)”

• SetbacksSpecified

  RL residential zone inside SeaTac city limits.

  • Setback dimensions may change subject to landscaping requirements.
  • For new detached dwelling units, the minimum garage setback is 20 feet and all other structural portions are 15 feet; this does not apply to additions to existing detached dwelling units.

  minimum front yard setback: 15 feet (New detached-unit garages require 20 feet; landscaping requirements may change the dimension.) · minimum side yard setback: 5 feet (Landscaping requirements may change the dimension.) · minimum rear yard setback: 15 feet (Landscaping requirements may change the dimension.)

  “MINIMUM FRONT YARD SETBACK | 15' (1) | 15' | 15' | 10' | 0' | N/A | Setback dimensions may change subject to landscape requirements. [...] MINIMUM SIDE YARD SETBACK | 5' | 5' (1) | 5' (1) | 5' | 5' | 5' [...] MINIMUM REAR YARD SETBACK | 15' | 10' (1) | 10' (1) | 5' | 5' | 5'”

• Lot coverageSpecified

  RL residential zone inside SeaTac city limits.

  • Lot coverage applies to the total development site.

  maximum building lot coverage: <= 50 percent (Lot coverage applies to total development site.)

  “MAXIMUM BUILDING LOT COVERAGE | 50% | 55% | 55% | 75% | 90% | N/A | (1) Lot coverage applies to total development site.”

Still unanswered

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

• Owner-builder exemption — Owner-built residential construction inside SeaTac city limits.
• Certificate of occupancy — Residential occupancy inside SeaTac city limits.
• Minimum dwelling size — Dwellings in the RL residential zone inside SeaTac city limits.
• Living in an RV — RV occupancy on private land inside SeaTac city limits.
• Camping on your land — Temporary camping on private land inside SeaTac city limits.

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.

Off-grid gear

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

• Water Crystal Quest Filter any source — well, rain, or creek — to drinking-clean.
• Power Bluetti Solar generators and home battery backup for living off the grid.
• Septic Soil percolation test kit Run your own perc test before paying an engineer — the first thing a septic office asks about.
• Water Well water test kit Bacteria, nitrates, hardness — know what the well on a parcel is really pumping.

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