Case Study 02 — Load Path Failure

The Incomplete Load Path

The cripple wall was anchored. The permit was closed. One side of the house is almost entirely glass — and the retrofit drawings show hardware running directly beneath it.

Anonymized composite · SDCI public permit records + Google Street View · Seattle, WA

A seismic retrofit is only as strong as the load path it completes. Lateral forces from an earthquake enter the structure at the roof, travel down through the walls, and must be transferred continuously into the foundation. Break the chain anywhere — a missing shear wall, a weak connection, a wall that exists on paper but not in the structure — and the retrofit does not work. The hardware becomes decoration.

The permit drawings for this property show cripple wall plywood and anchor bolts installed along the full foundation perimeter, including a long run beneath the front facade. A review of public street-level imagery shows what that facade is: nearly floor-to-ceiling windows, continuous glazing, no structural wall above. The cripple wall below it has been diligently anchored to a foundation. Above that foundation sits glass. There is no shear wall to receive the load. The retrofit anchors the bottom of a chain whose top link does not exist.

This is not a hidden condition. The window wall is visible from the street. It would be visible on any site visit, apparent in any photograph, obvious to any structural engineer evaluating the load path. The permit scope was drawn without accounting for what sits above the crawlspace — or the drawings were produced without anyone looking. Either way, the result is the same: work that satisfies a permit while leaving the structure's primary vulnerability unaddressed.

A complete retrofit requires tracing the load path from roof to foundation and confirming that each link transfers force to the next. Where a wall line is interrupted — by glazing, by a garage opening, by any condition that breaks continuity — the engineering has to account for it. Anchoring the foundation below a glass wall and calling it done is not a structural solution. It is a completed checklist.