Zoning, building permits and septic rules in Mountlake Terrace, Washington

Mountlake Terrace’s own rules

• Building permitRequired

  Construction, alteration, repair, demolition, occupancy change, and regulated electrical, gas, mechanical, or plumbing work inside Mountlake Terrace city limits.

  • Application to the Building Official and the required permit must be obtained before covered work.
  • Permit exemptions identified in adopted-code amendments remain applicable.

  “No person, firm, or corporation shall construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or erect, install, enlarge, alter, repair, convert, or replace any electrical, gas, mechanical or plumbing system, the installation of which is regulated by this chapter, or cause any such work to be done, without first making application to the Building Official and obtaining the required permit.”

• Building code adoptedAdopted (with conditions)

  Buildings and structures inside Mountlake Terrace city limits.

  • The chapter references the 2021 IBC, IRC, IMC, UPC, IECC, IEBC, and other listed codes, with stated Washington amendments and local amendments.

  International Building Code edition: 2021 (With Washington amendments and local amendments.) · International Residential Code edition: 2021 (With Washington amendments and local amendments.)

  “The following codes are referenced for the purpose of establishing rules and regulations for the construction, alteration, removal, demolition, equipment, use, occupancy, location and maintenance of buildings and structures:”

• InspectionsRequired

  Work regulated by MTMC Chapter 15.05 inside Mountlake Terrace city limits.

  • Work must conform with applicable adopted codes.

  “All such work is subject to inspection by the City and must conform with the applicable adopted codes.”

• Zoning districtsPublished (with conditions)

  Land inside Mountlake Terrace city limits.

  • Residential districts are shown on the City's Official Zoning Map.
  • Other Title 19 districts and overlays may apply.

  “The following residential districts (R districts) are intended to provide land for single-unit residences, middle housing, and other complementary uses which serve the neighborhood and have been deemed compatible with residential character. Middle housing brings inherent public benefits such as increased housing supply and choice, housing at relatively more "attainable" price points, increased walkability, and transportation-supportive neighborhoods. The R districts are depicted on the City's Official Zoning Map.”

• SetbacksDistrict specific (with conditions)

  Development in Mountlake Terrace residential districts.

  • Applicable setbacks are in the Dimensional Requirements Table 19.30.030.
  • ADU setbacks and building-separation distances are governed by that table; no setback is required from an alley.

  “Setbacks. Minimum setbacks and building separation distances for ADUs are set forth in the Dimensional Requirements Table 19.30.030. No setback is required from any alley.”

• Lot coverageDistrict specific (with conditions)

  Parent lots in Mountlake Terrace R-1, R-2, R-3/RML, and R-4/RMM residential districts.

  • Coverage includes ADUs.
  • The table allows noncumulative coverage bonuses.

  maximum lot coverage by structures: 45-65 percent of lot area (Varies by residential district; includes ADUs.)

  “Lot Coverage by Structures (including ADUs) Maximum Lot Coverage (percent of lot area) | 45% | 50% | 60% | 65% Additional Lot Coverage for Bonuses | +5% Lot coverage bonuses are not cumulative”

• Building heightDistrict specific (with conditions)

  Buildings in Mountlake Terrace R-1, R-2, R-3/RML, and R-4/RMM residential districts.

  • Height is separately regulated in the front 75 percent and rear 25 percent of mean lot depth.
  • Listed stack-housing and bonus exceptions, rooftop access structures, roof-deck walls or railings, and photovoltaic-panel exceptions apply as stated in the table.

  maximum front building height: 3 stories, 35 feet (Higher limits are stated for stack housing and bonuses in some districts.) · maximum rear building height: 2 stories, 25 feet to 3 stories, 35 feet (Varies by district and stated bonuses.)

  “Building Height Standards Maximum Building Height at Front of Lot | 3 stories, 35 feet | 3 stories, 35 feet | | Exception for "Stack" Housing Form Type: 4 stories, 45 feet | | With Bonuses: 4 stories, 45 feet Maximum Building Height at Rear of Lot | 2 stories, 25 feet | 3 stories, 35 feet”

• Manufactured homesAllowed (with conditions)

  Manufactured homes on residential lots inside Mountlake Terrace city limits.

  • Must meet Title 19 development standards and all other applicable single-unit regulations.

  “A manufactured home shall be permitted to locate on any residential lot when it meets the development standards of this title and all other applicable regulations for single units are met.”

• Accessory dwellingsAllowed (with conditions)

  Accessory dwelling units on lots inside Mountlake Terrace city limits.

  • Up to two ADUs may be allowed on a lot without counting toward maximum density.
  • An ADU is subject to size, location, height, setback, utility, critical-area, health-and-safety, and building-permit requirements.

  maximum ADUs per lot: <= 2 ADUs (May be allowed without counting toward maximum density calculations.) · ADU floor area: 200-1000 square feet (Garage areas excluded.)

  “Two accessory dwelling units may be allowed”

• Who permits septicLocal (with conditions)

  Individual sewage disposal systems inside Mountlake Terrace city limits.

  • A City permit is required for construction, installation, or alteration.

  “permit from the City of Mountlake Terrace”

• Septic permitRequired

  Construction, installation, or alteration of an individual sewage disposal system inside Mountlake Terrace city limits.

  • The code states a $5.00 permit fee payable to the City.

  septic permit fee: 5 USD

  “On and after the effective date of the ordinance codified in this article, no person, firm or corporation shall construct, install or alter an individual sewage disposal system without first having obtained a permit from the City of Mountlake Terrace; said permit to be issued on receipt of a permit fee of $5.00 payable to the City of Mountlake Terrace, to be used to help defray the costs of carrying out the provisions of these rules and regulations.”

• Off-grid sanitationLimited

  Individual sewage disposal systems inside Mountlake Terrace city limits.

  • City permit required for construction, installation, or alteration.
  • Municipal sewer connection is required where the availability and distance conditions in MTMC § 13.20.040 apply.

  “On and after the effective date of the ordinance codified in this article, no person, firm or corporation shall construct, install or alter an individual sewage disposal system without first having obtained a permit from the City of Mountlake Terrace;”

• Mandatory utility hookupSewer (with conditions)

  Buildings with plumbing inside Mountlake Terrace city limits where municipal sewer service is available.

  • Existing buildings within 200 feet of a sewer main or street containing a sewer main must connect within 90 days after written notice.
  • A building constructed after sewer service is available to the property must connect immediately as part of construction.
  • Annexed or newly served properties may delay connection up to three years only if the listed certification, pumping, no-further-development, and fee conditions are met.

  distance from sewer main or street containing sewer main: <= 200 feet · connection deadline after written notice: <= 90 days (Where service is available.)

  “Every dwelling, house, hotel, apartment, tenement, factory, store, or other building in which plumbing arrangements have been or are to be placed, shall be connected with the municipal sanitary sewerage system within 90 days after written notice that sewer service is available to said building; and provided, that any such building or part of building shall be located within 200 feet of a sewer main or a street where a sewer main is located; and provided further, that if any such building is constructed after sewer service is available to the property upon which it is located, then the connection shall be made immediately as an integral part of the construction;”

• Permit feesVariable (with conditions)

  Permits required under MTMC Chapter 15.05 inside Mountlake Terrace city limits.

  • Fees are established under MTMC § 3.150.090.
  • Unpermitted work may be subject to an investigation fee equal to the required permit fee.
  • Refund limitations stated in MTMC § 15.05.220 apply.

  “Permit fees partly or fully pay for City services to ensure development is appropriately planned, built, installed, inspected, or otherwise carried out consistent with applicable codes. Permit fees are established pursuant to MTMC § 3.150.090. Whenever a permit is required under this chapter, the appropriate fees shall be paid to the City.”

• Permit processPartial

  Work regulated by MTMC Chapter 15.05 inside Mountlake Terrace city limits.

  • The code requires an application to the Building Official and obtaining the required permit before covered work.
  • The opened provision does not provide a complete procedural checklist.

  “No person, firm, or corporation shall construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or erect, install, enlarge, alter, repair, convert, or replace any electrical, gas, mechanical or plumbing system, the installation of which is regulated by this chapter, or cause any such work to be done, without first making application to the Building Official and obtaining the required permit.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Mountlake Terrace or Snohomish County directly.

• Owner-builder exemption — Owner-performed residential construction inside Mountlake Terrace city limits.
• Certificate of occupancy — New or changed residential occupancy inside Mountlake Terrace city limits.
• Minimum dwelling size — Primary dwellings in Mountlake Terrace residential districts.
• Living in an RV — RV occupancy on private land inside Mountlake Terrace city limits.
• Camping on your land — Temporary private-land camping inside Mountlake Terrace 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 Mountlake Terrace 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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