Mercer Island, Washington Building Permit Guide

On Mercer Island, Community Planning and Development (CPD) issues building permits, and its Building Team, led by the Building Official, also reviews and inspects electrical, plumbing and mechanical work, because the City runs its own electrical program instead of Labor and Industries. Plans go to the City’s online Permit Submittal Portal; over-the-counter reviews are not being offered. Under the fee schedule effective August 1, 2026, plan check costs 70% of the building permit fee, and a first review of a major building permit has a 4-week target.

CPD’s address is 9611 SE 36th Street, Mercer Island, WA 98040; its permit services team answers 206-275-7605 and epermit.tech@mercerisland.gov. The island had 25,422 residents in the Census estimate for 2025.

CPD handles permits for property inside the City of Mercer Island.

What requires a building permit on Mercer Island?

The permit rules are in Mercer Island City Code (MICC) 17.14.010, which sets 22 kinds of building permit exemptions. The City adds a limit for its hazard areas: none of the exemptions applies in a flood hazard area or a City critical area (steep slopes, landslide, erosion and seismic hazards, wetlands and streams) unless the work is entirely within or on the outside surface of an existing legal building.

Retaining walls get a closer reading on the City’s page: a wall is exempt only if it is no more than 4 feet from the bottom of the footing to the top, has flat ground above and below, carries no surcharge from a driveway, building or fence, stands on private property (or in the street under a street occupancy permit) and is outside every critical area. A homeowner may also choose to apply for a permit for exempt work, such as a tree house or arbor, to have the setbacks and height checked.

What the city decides and what the state holds

The construction codes are the state’s 2021 editions, in force since March 15, 2024. Mercer Island sets its own exemption list and critical-area limit, the 2-year permit term and renewal rules, the wet season ban on earthwork, its Shoreline Master Program, tree rules, construction hours and the fee schedule. Its electrical program means electrical permits and inspections are the City’s, which L&I’s list of city programs confirms.

Washington has a mandatory statewide building code under chapter 19.27 RCW that every city and county enforces and may make stricter; electrical permits come from the Department of Labor and Industries unless the city runs its own program or Tacoma Power serves the site. Building codes in Washington

Who handles permitting on Mercer Island?

CPD’s Building Team (the Building Official, plans examiners and inspectors) covers building, electrical, plumbing, mechanical, energy and accessibility code review. The Land Use Planning Team handles zoning decisions, short plats, shoreline permits, variances and design review; development review engineers handle stormwater and utilities; and the Fire Marshal’s Office reviews fire protection for commercial, residential and special projects, with fire inspections requested through Eastside Fire & Rescue.

Permit types

Residential permits

Simple residential projects (non-structural interior remodels, basic decks outside hazard areas and buffers, skylights, window or door size changes and minor repairs) still need a full electronic submittal, since over-the-counter review is suspended. Every single-family application includes the application form with an estimated valuation, the Single Family Plan Coversheet, a fire area and valuation form, a water meter sizing worksheet when fixtures are added or more than one bathroom or kitchen is re-piped, and a site development worksheet when work goes outside the house or adds floor area. Homeowners doing their own work file the owner-as-contractor form, and the City asks applicants to check that their contractor holds a Mercer Island business license.

Additions under 500 sq ft may skip intake screening; additions of 500 sq ft or more, and new houses, are substantial residential projects that may need a paid intake screening ($903) before the application is accepted. Plan sets must be one bookmarked, landscape PDF printable at 11 by 17 inches or larger, with forms as separate PDFs and no security settings, or the submittal is treated as incomplete.

Building or remodeling a home here? Alliance handles residential permit expediting, so the crew isn't waiting on the counter.

Commercial permits

Commercial and multifamily projects use the commercial submittal requirements; their electrical permits normally need plan review, and a commercial or multifamily re-roof always needs a permit. Fire protection review for non-single-family buildings ranges from $182 under 3,000 sq ft to $6,990 over 50,000 sq ft, and a temporary certificate of occupancy costs $6,202.

For tenant improvements and new commercial builds, Alliance handles commercial permit applications through issuance. More on this: commercial building permits explained.

What comes before the building permit

Steep slopes shape many projects. A geotechnical report by a Washington-licensed engineer, with a statement of risk, is required where a structure sits in a landslide, steep slope, seismic or erosion hazard area, and the City’s review costs $691 plus peer review for a house. From October 1 to April 1, clearing, grading, filling and foundation work are banned in landslide hazard areas and where more than 2,000 sq ft of an erosion hazard area would be disturbed, unless the Building Official grants a wet season waiver backed by a geotechnical evaluation. On the shoreline, most work needs either a shoreline exemption ($1,092) or a shoreline substantial development permit ($10,920); an owner-occupied house no taller than 35 feet is exempt from the substantial development permit but still needs the exemption. Residential building permits that need public notice carry a 30-day comment period, and review cannot finish before it ends.

Mercer Island permit costs and fees

Construction fees are in section 8 of the City’s 2026 fee schedule, as amended by Resolution No. 1698 effective August 1, 2026 (the “2nd revised” 2026 schedule). The 2026 hourly staff rate for every review discipline is $182. The schedule does not list the State Building Code Council fee.

Worked example. A $60,000 house remodel: $1,091.17 plus 10 × $11.67 ($116.70) is a building permit fee of $1,207.87. Plan check at 70% adds $845.51, for $2,053.38; if the remodel includes mechanical, electrical and plumbing work under a combination permit, 31% adds $374.44, and the $261 energy compliance fee for an alteration applies where required.

New homes pay impact fees at the rate in force when the permit is issued: $4,318.02 for transportation and $6,314.30 for parks per single-family home or middle-housing unit of one or two dwellings ($1,929.74 and $3,157.14 for an ADU); the school impact fee has been $0 since the school district reduced it in 2020. Water and sewer connection charges, and a Seattle Public Utilities facilities charge on new and upsized water services, are collected by the City.

Trade permits and who may pull them

Electrical, plumbing and mechanical permits all come from the City. Work tied to a building permit is normally issued as a combination permit priced as a share of the building permit fee; stand-alone permits use the unit fee lists, with a $214 minimum (a $46 issuance fee for electrical) and $120 for simple jobs such as a like-for-like water heater exchange without new gas piping or a temporary power service. Single-family electrical permits can be bought online at MyBuildingPermit, and a single-family side sewer repair can be self-issued there.

How to apply for a Mercer Island building permit

Review, corrections and what causes delay

The City’s targets are 2 weeks for an intake screening, 1 week to route a complete application, 4 weeks for a first review of a major building permit and 2 weeks for a non-major one, 2 weeks for each later round and 1 week to prepare the permit for issuance; trade permits target 2 weeks and fire permits 3. The clock starts only once all required documents are in. The 30-day public comment period can lengthen review, and earthwork on hazard lots may have to wait out the wet season. Applications expire 18 months after filing, with extensions only while SEPA review, other City review or litigation is under way.

Inspections on Mercer Island

Most inspections are requested on MyBuildingPermit, which offers same-day service for many inspection types when the request is in by 6 a.m. Concrete, foundation and wall inspections must be requested at least three business days before the pour. The signed plan coversheet is the inspection record and must be on site with the approved plans. Fire system inspections are requested through Eastside Fire & Rescue’s online form, with up to 72 hours’ notice. Construction is allowed from 7 a.m. to 7 p.m. on weekdays and 9 a.m. to 6 p.m. on Saturdays, never on Sundays or City holidays.

A building permit expires two years after it is issued. It can be renewed if it is still active or expired no more than 90 days earlier, for 50% of the original building permit fee and with no change of scope; if the final is not passed within three years of issue, the remaining work needs new permits under the codes and fees then in force.

Mercer Island permit search and official resources

Permit status, inspection results and expiration dates can be searched by address on MyBuildingPermit.com. In FEMA’s Community Status Book, Mercer Island is a participating community whose map shows no special flood hazard area (all zone C).

• Mercer Island Building team page
• When a building permit is required (MICC 17.14.010 exemptions)
• Residential building permits
• Simple residential projects
• How to upload a submittal
• Review timelines
• Permit fees page
• 2026 fee schedule, effective August 1, 2026 (PDF)
• Permit extension and renewal
• Inspections
• Wet season work waiver
• Shoreline management
• Electrical permits
• MyBuildingPermit.com

Mercer Island building permit FAQ

Who issues building and electrical permits on Mercer Island?

The City’s Community Planning and Development department; electrical permits are the City’s, not L&I’s.

Can I get a permit over the counter?

Not at present. Simple residential permits are submitted electronically through the Permit Submittal Portal.

Do I need a permit to re-roof?

For a house, only when sheathing is replaced or the roofing material changes; an in-kind re-roof over the existing sheathing is exempt. The permit costs $214.

How much is a building permit?

For a $60,000 remodel, $1,207.87 plus $845.51 plan check under the August 2026 schedule, with 31% more for a combination trade permit.

Can I dig foundations in winter?

Not on landslide hazard lots, or over 2,000 sq ft of erosion hazard land, between October 1 and April 1 without a wet season waiver.

How long is a permit good for?

Two years from issue, renewable for 50% of the original building permit fee if you apply before or within 90 days after it expires.

Do I need a permit to remove a tree?

Almost always; single-family tree removal permits start at $214 for one to three trees.

Simplify Mercer Island permitting with Alliance Permitting

Alliance Permitting is a permit documentation and submission company in Washington. We prepare your paperwork, file it correctly and coordinate with the permitting authority through issuance. We are not a contractor and we do not perform licensed plan review or inspections; that work stays with your licensed team and the jurisdiction.

This guide is provided by Alliance Permitting for general information about Mercer Island permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.