Addition permits in Sammamish: fees, timeline & requirements (2026)
Everything you need to know about pulling a home addition permit in Sammamish, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Sammamish Community Development.
Free lookup, no account needed — your lot polygon, zoning, setbacks and overlays, cited to Sammamish's source.
When does a home addition need a permit in Sammamish?
Single-family/duplex additions require a building permit (MBP: Building → Single-Family Residential → Structure Addition). Demolitions, pools, retaining walls, and detached structures require separate permits. A Sewer Availability Certificate is required when the project exceeds 50% of the assessed value or adds plumbing fixtures.
How long a home addition permit actually takes in Sammamish
34 permits issued in the last 12 months: half were issued within 118 days of application and 80% within 219 (over-the-counter and plan-reviewed together; the City's records do not separate them).
Days from application to issue, measured by Kolmo from City of Sammamish residential building permits ("BLDG RESIDENTIAL" types) on MyBuildingPermit.com.
In the source's own words
“Please note that demolitions, pools, retaining walls, and detached structures require submittal of a separate demolition or building permit.”Source ↗verified 2026-05-29
Required submittals
- Acceptance of Financial Responsibility (Affidavit of Applicant Status)
- Historic Resources Affidavit
- Legal Description
- Plan Set (existing + proposed)
- Project Narrative
- Residential Fixture Count Form
- Sewer Availability Certificate (when >50% assessed value or fixtures added)
Inspection sequence
- Foundation/footing
- Plumbing rough-in
- Electrical rough-in
- Mechanical rough-in
- Framing
- Insulation
- Drywall
- Final
Contractor specialties needed
General contractor · Electrician (journey-level 01 or residential 02) · Plumber · Mechanical contractor
Who can do this work in Sammamish?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout Sammamish and King County. Kolmo prepares the drawings and submittals, files the home addition permit with Sammamish Community Development, carries the project through review and inspections, and performs the construction. Call (206) 410-5100 for a Sammamish home addition quote.
Notes & caveats
2021 IRC R301 governs framing. WSEC R402.1 sets envelope requirements. New conditioned space requires Manual J HVAC sizing. Lateral load path continuity required for vertical additions.
Addition permit fee estimate in Sammamish
Worked example for a $120,000 home addition project (building permit). Your actual fee scales with project valuation.
| Building permit fee | $1,451.51 |
| Plan review | $943.48 |
| Technology surcharge | $359.25 |
| WA state surcharge | $6.50 |
| Estimated total | $2,760.74 |
Sammamish prices an addition's building permit on the value of the work: $994.39 for the first $50,000 plus $5.68 for each $1,000 more up to $100,000, and $1,278.51 for the first $100,000 plus $8.65 for each $1,000 more up to $500,000, with plan review at 65% of the permit fee. Planning's review of the building application is a $753 flat fee for an addition or remodel, and the energy code review $91. A residential combination plumbing or mechanical permit is $134 for up to 3 items and $45 for each more, and the City's electrical permit is priced on the value of the electrical work, $92.33 up to $250 and $215.45 for the first $2,000 plus $18.73 for each $1,000 more up to $25,000. The City adds a 15% technology fee to each fee (2026 Fee Schedule). Apply via mybuildingpermit.com. Computed from Sammamish's adopted fee schedule · source ↗. Land use, fire and engineering review, intake, impact and utility fees, where they apply, are charged separately.
How to apply yourself
- 1. Confirm your parcel's zoning & overlays. Run an address lookup for your home addition in Sammamish — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline, critical-area or historic overlays.
- 2. Assemble submittals: the 7 documents under Required submittals above.
- 3. Submit through the city portal: Sammamish Community Development ↗
- 4. Track review. Respond to reviewer comments promptly.
- 5. Pay issuance fees (about $2,761 for a $120,000 project) and pick up the permit. Inspection card travels with the job.
Or have Kolmo do it
Kolmo prepares the drawings and submittals, files with Sammamish Community Development, handles reviewer comments, and builds the project.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
Addition permits in Sammamish — FAQ
When does a home addition need a permit in Sammamish?
Single-family/duplex additions require a building permit (MBP: Building → Single-Family Residential → Structure Addition). Demolitions, pools, retaining walls, and detached structures require separate permits. A Sewer Availability Certificate is required when the project exceeds 50% of the assessed value or adds plumbing fixtures.
How much does a home addition permit cost in Sammamish?
For a $120,000 home addition project, the estimated Sammamish permit fee is about $2,760.74 (building fee $1,451.51 + plan review $943.48 + surcharges) from Sammamish's adopted fee schedule. Land use, fire and engineering review, intake, impact and utility fees, where they apply, are charged separately.
How long does it actually take to get a home addition permit in Sammamish?
34 permits issued in the last 12 months: half were issued within 118 days of application and 80% within 219 (over-the-counter and plan-reviewed together; the City's records do not separate them). Measured by Kolmo from City of Sammamish residential building permits ("BLDG RESIDENTIAL" types) on MyBuildingPermit.com.