Structural engineering — wall removals, addition framing, tie-in

What's different about this engineering scope

A second-story addition's structural design is dominated by carrying new load down through existing walls to the foundation. A whole-house remodel + addition is dominated by horizontal load redistribution: every interior wall you remove is a former bearing wall that needs a beam, posts, and a load path to the foundation, plus a new addition that has to integrate without differential settlement.

What the engineer designs

A licensed Washington structural engineer designs:

1. Addition foundation. Per the tie-in strategy from step 1.3 — continuous footing, stepped joint, or independent foundation with structural connection above grade.
2. Addition framing. New floor joists, exterior wall framing, roof framing for the new footprint.
3. Roof tie-in. How the new roof integrates with the existing — usually a flush ridge, a stepped ridge, or a shed-off-the-existing.
4. Interior wall-removal beams. For each bearing wall coming out, a beam (LVL, steel, glulam) sized to the span and load, with posts at each end and a continuous load path to the foundation.
5. Lateral retrofit if substantial alteration triggers. When the project trips the substantial-alteration threshold (next step), the engineer may need to design retrofit shear walls and holdowns to bring the existing house to current code.

What the deliverable looks like

A structural drawing set — typically 6–10 sheets — plus a calculations package. The drawings carry the engineer's stamp and Washington license number on every sheet. Calcs are a separate PDF, often 40–100 pages.

Wall-removal logic — the main intellectual work

For each candidate wall removal, the engineer answers:

• Is it bearing? Run the load path from roof to foundation. Walls that intercept the path are bearing.
• What's the span? Distance between supports decides beam size.
• Where do the posts land? New posts have to bear on something (a beam below, a foundation pad, a continuous wall). The post location decides whether the open plan actually works visually.
• What's the load path to the foundation? New posts that bear on a basement beam need that beam sized too. New posts that need a new foundation pad mean digging into the basement floor.

A clean wall-removal design might be 3–4 LVLs with posts that fall on existing pilasters. A messy one might require a steel beam, new basement posts, new pad footings, and a retrofit shear wall on the floor above. The engineer picks the cheapest path that meets code.

Coordination with kitchen design

The structural and kitchen designs have to be done together. The beam over the kitchen-living opening can't drop into the island. The post on the corner of the island has to fall where the cabinets allow. The kitchen lighting plan can't fight the beam. Coordinating in design, not in the field, is what keeps the build clean.

When this is done

When you have a stamped structural set that the designer has integrated into the architectural drawings without conflict. The combined set is permit-ready, pending the substantial-alteration analysis.