Custom House Plans in Seattle, WA

What's different about building in Seattle

• ★The Seattle Department of Construction & Inspections applies the Seattle Residential Code with local amendments.
• ★Environmentally Critical Areas (steep slopes, landslide-prone) require geotechnical review.

Building requirements

Building a house in Seattle, WA: what the code requires

Statewide residential code

Building code

Washington State Residential Code (IRC-based with state amendments) applies statewide.

Energy code

The Washington State Energy Code – Residential is among the strictest in the US (energy credits system).

Climate zone

IECC climate zone 4–6. Insulation, windows and HVAC are sized to match.

Typical frost depth

12–18 in (west), 24–30 in (east). Footings must extend below the local frost line (confirm with your building department).

Foundations

Crawlspace or basement, depending on soil and lot slope.

Who can draw the plans

Single-family homes can generally be designed by a non-licensed home designer. A licensed engineer's stamp is often required for structural items, engineered foundations or special hazard zones, or when the local building official asks for it.

Engineer stamp

If your jurisdiction requires sealed drawings, add our Washington Engineer Stamp / Permit-Ready package ($1,000).

Washington-specific rules & hazards

• ●Seismic design required west of the Cascades.
• ●Critical areas ordinances (wetlands, steep slopes) and shoreline permits apply.
• ●Wildland-urban interface rules in eastern Washington.
• ●Seismic bracing, shear walls and hold-downs
• ●Heavy roof snow loads and steeper, well-braced roof framing
• ●Wildfire-resistant materials and defensible-space detailing

Summary for planning only. Codes, editions and local amendments change, so always confirm current requirements with the building department that will issue your permit. Our designers check your jurisdiction before drawing.

Towns, villages & rural counties

Permit checklist for building in Seattle and surrounding towns

Requirements differ town by town. Use this checklist with your local building, zoning and health departments, and include what you learn in your design instructions. We'll draw to it.

1. 01Find who issues permitsIncorporated towns and cities usually have a building department. In unincorporated areas it's the county building or planning office, or a state agency, or in some rural areas nobody. Call before you buy the lot.
2. 02Zoning & setbacksCheck the zoning district for minimum lot size, front, side and rear setbacks, maximum height, lot coverage and whether barndominiums, ADUs or metal buildings are allowed.
3. 03HOA & deed restrictionsSubdivisions often restrict minimum square footage, exterior materials, roof pitch, garage orientation and outbuildings. These can be stricter than the town code.
4. 04Septic & well permitsWithout city sewer or water, you'll need a percolation (perc) test and a septic permit from the county health department, plus a well permit.
5. 05Driveway & culvert permitConnecting to a public road usually needs a driveway or culvert permit from the town, county or state DOT.
6. 06Floodplain development permitIf any part of the lot is in a FEMA flood zone, you'll need a floodplain permit and an elevation certificate, and the lowest floor must be at or above the Base Flood Elevation plus any local freeboard.
7. 07Energy code complianceMost jurisdictions require an energy compliance report (REScheck or similar) showing insulation, windows and HVAC meet the adopted energy code.
8. 08Engineering stampMany building officials require a licensed engineer's seal for foundations, beams, trusses, or high wind, snow or seismic zones. Add our Engineer Stamp option at checkout.
9. 09Utility & fire accessRural lots may need a fire-apparatus access road, a water supply for firefighting, or wildfire (WUI) defensible-space and ignition-resistant materials.
10. 10Inspections scheduleA typical sequence is footing, foundation, framing, rough MEP, insulation and final. A certificate of occupancy is issued after final inspection.

Popular styles around Seattle

From $1,250

Craftsman Plans in Washington

Tapered columns, exposed rafter tails, stone bases and handcrafted detail.

From $1,300

Modern Plans in Washington

Clean lines, flat or shed roofs, floor-to-ceiling glass and indoor-outdoor living.

From $1,050

Cabin & A-Frame Plans in Washington

Timber, steep A-frames and big windows made for mountain or lake lots.