Addition permits in City of Sammamish: fees, timeline & requirements (2026)
Everything you need to know about pulling a home addition permit in City of 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 Apply via MyBuildingPermit.com..
When does a home addition need a permit in City of 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.
From City of Sammamish's own page
“Please note that demolitions, pools, retaining walls, and detached structures require submittal of a separate demolition or building permit.”Source ↗verified 2026-06-26
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, electrical-01-or-02, plumbing, mechanical
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. Most WA cities use a uniform fee bracket (UBC Table 1-A) for the building permit; plan review fee is typically 65% of building permit fee.
Addition permit fee estimate in City of Sammamish
Worked example for a $120,000 home addition project (building permit). Your actual fee scales with project valuation.
| Building permit fee | $1,105.75 |
| Plan review | $718.74 |
| WA state surcharge | $4.5 |
| Estimated total | $1,828.99 |
Plan-review fee scales with valuation per UBC Table 1-A. State surcharge $4.50 per building permit. Trade permits (E/P/M) separate. Apply via https://mybuildingpermit.com. Computed from the City of Sammamish fee bracket schedule · source ↗. Impact/utility fees may apply separately.
How to apply
- 1. Confirm your parcel's zoning & overlays. Run an address lookup for your City of Sammamish home addition — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline/ECA/historic overlays.
- 2. Assemble submittals (7).
- 3. Submit through the city portal: Apply via MyBuildingPermit.com. ↗
- 4. Track review (typical: 30–120 days). Respond to reviewer comments promptly.
- 5. Pay issuance fees (Plan-review fee scales with valuation per UBC Table 1-A. State surcharge $4.50 per building permit. Trade permits (E/P/M) separate. Apply via https://mybuildingpermit.com.) and pick up the permit. Inspection card travels with the job.
Addition permits in City of Sammamish — FAQ
When does a home addition need a permit in City of 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 City of Sammamish?
For a $120,000 home addition project, the estimated City of Sammamish permit fee is about $1,828.99 — building fee $1,105.75 + plan review $718.74 + surcharges. Fees scale with project valuation per the city schedule.
How long does City of Sammamish take to review a home addition permit?
Typical review window: 30–120 days.