Addition permits in City of Issaquah: fees, timeline & requirements (2026)
Everything you need to know about pulling a home addition permit in City of Issaquah, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Community Planning & Development.
When does a home addition need a permit in City of Issaquah?
A permit is required for all single-family/duplex new construction and additions; no exemption is published. Setback / form / intensity per IMC 18.404.
From City of Issaquah's own page
“This permit is required for construction of single family / duplex new construction and additions.”Source ↗verified 2026-06-26
Required submittals
- site plan with north arrow, property lines, setbacks, existing + proposed structures, lot coverage calculation
- floor plan existing and proposed (dimensioned, 1/4" = 1' min)
- elevations all affected sides (existing + proposed, height-to-grade)
- foundation plan + footing details (if footprint addition)
- framing plan (floor + roof + lateral)
- wall section with insulation values per WSEC
- structural calculations (when ≥500 sqft addition or out of IRC prescriptive envelope)
- WSEC compliance form (Energy Code Compliance Certificate)
- Manual J HVAC sizing calculation for new conditioned area
- window/door schedule with NFRC U-factor and SHGC values
- soils report if footing on slope or expansive soils
Inspection sequence
- foundation/footing
- plumbing rough-in
- electrical rough-in
- mechanical rough-in
- framing
- insulation
- drywall
- final
Contractor specialties needed
general, plumbing, mechanical
Notes & caveats
Submit via MyBuildingPermit.com (paper not accepted). Setback / form / intensity per IMC 18.404; design standards per applicable overlay (Olde Town, Issaquah Highlands, etc.).
Addition permit fee estimate in City of Issaquah
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 Issaquah 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 Issaquah home addition — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline/ECA/historic overlays.
- 2. Assemble submittals (11).
- 3. Submit through the city portal: Community Planning & Development ↗
- 4. Track review (typical: 45–120 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 Issaquah — FAQ
When does a home addition need a permit in City of Issaquah?
A permit is required for all single-family/duplex new construction and additions; no exemption is published. Setback / form / intensity per IMC 18.404.
How much does a home addition permit cost in City of Issaquah?
For a $120,000 home addition project, the estimated City of Issaquah 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 Issaquah take to review a home addition permit?
Typical review window: 45–120 days.