Addition permits in Issaquah: fees, timeline & requirements (2026)
Everything you need to know about pulling a home addition permit in 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.
Free lookup, no account needed — your lot polygon, zoning, setbacks and overlays, cited to Issaquah's source.
When does a home addition need a permit in 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.
In the source's own words
“This permit is required for construction of single family / duplex new construction and additions.”Source ↗verified 2026-05-29
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 contractor · Plumber · Mechanical contractor
Who can do this work in Issaquah?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout Issaquah and King County. Kolmo prepares the drawings and submittals, files the home addition permit with Community Planning & Development, carries the project through review and inspections, and performs the construction. Call (206) 410-5100 for an Issaquah home addition quote.
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 Issaquah
Worked example for a $120,000 home addition project (building permit). Your actual fee scales with project valuation.
| Building permit fee | $1,542.86 |
| Plan review | $1,002.86 |
| Technology surcharge | $152.74 |
| WA state surcharge | $6.50 |
| Estimated total | $2,704.96 |
Issaquah prices an addition's building permit on the value of the work: $544.06 for the first $25,000 plus $14.23 for each $1,000 more up to $50,000, $895.06 for the first $50,000 plus $9.44 for each $1,000 more up to $100,000, and $1,381.06 for the first $100,000 plus $8.09 for each $1,000 more up to $500,000. Plan review adds 65% of that fee, a 6% technology surcharge is added to both, and the state building code fee is $6.50. Plumbing is $31.44 for each new or moved fixture and mechanical $62.88 for each new appliance or duct system, each $62.88 at the least and $422.04 at the most, with a separate technology fee. Electrical permits come from L&I, not the City, at L&I's fees. Apply via mybuildingpermit.com. Computed from Issaquah'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 Issaquah — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline, critical-area or historic overlays.
- 2. Assemble submittals: the 11 documents under Required submittals above.
- 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 (about $2,705 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 Community Planning & Development, handles reviewer comments, and builds the project.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
Addition permits in Issaquah — FAQ
When does a home addition need a permit in 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 Issaquah?
For a $120,000 home addition project, the estimated Issaquah permit fee is about $2,704.96 (building fee $1,542.86 + plan review $1,002.86 + surcharges) from Issaquah's adopted fee schedule. Land use, fire and engineering review, intake, impact and utility fees, where they apply, are charged separately.
How long does Issaquah take to review a home addition permit?
Typical review window: 45–120 days.