Full structural engineering for the addition + retrofit

What the engineer designs

For a second-story addition, the structural package covers:

• The new second-story framing — walls, floors (which are the new ceiling of the first floor), roof, lateral system.
• Load path through the existing house — how the new loads travel down through existing walls and into the foundation. This is where most of the engineering effort goes.
• Modifications to existing framing — new beams or posts at the new stair, sistered joists where load increases, hold-downs at shear walls.
• The foundation retrofit or new foundation designed in coordination with the geotech (if any).
• Seismic upgrades triggered by Seattle code or by SDCI Tip 314 if the project hits the substantial-alteration threshold (see step 3.1).

Cost

Full second-story addition: typically $5,000–$12,000 of structural engineering, with the high end driven by complex existing conditions or a full house lift.

Why this is its own step

The engineer needs the schematic locked before they engineer to it; the designer needs the engineering before they finalize the construction documents. That's why design and engineering ping-pong in this sequence rather than running in parallel.

What "stamped" means

The engineer signs and seals each sheet they're responsible for. SDCI requires a Washington-licensed engineer's stamp on the structural sheets at submittal. Verify the engineer's license at WA DOL.