This is the single most consequential gate on the whole project. The engineer's letter tells you whether the existing foundation can carry a second story, whether it needs a $15K–$60K retrofit, or whether you're in lift-and-replace territory. None of those is bad news — but you need to know which one applies before you spend on full design.
What gets inspected
The engineer looks at:
- Foundation type — brick-and-mortar, unreinforced concrete, reinforced concrete, post-and-pier.
- Footing depth and width — exposed at one or two points if not visible.
- Cracking, settlement, and lateral movement — visual + level readings.
- Connections to the framing above — anchor bolts (or absence of them), sill condition, hold-downs.
- Rim joist condition — rot, insect damage, water staining.
What the letter tells you
The engineer issues a short letter with three possible outcomes:
- Foundation adequate as-is. Rare for pre-1940 houses; common for post-1980 ones. You can build a second story on the existing foundation with seismic anchor improvements only.
- Foundation adequate with retrofit. Most common case. You'll add steel reinforcing, additional footings, or a perimeter beam. Cost typically $15,000–$60,000 depending on scope.
- Foundation not adequate. Either build a new foundation under the existing house (with the house lifted on temporary supports — see step 2.2) or accept that this is a teardown-rebuild instead of an addition.
Why you do this in Phase 1, not Phase 2
A second story can't be designed without knowing what's carrying the load. If the engineer's report says "lift required," the design strategy changes substantially — different staging, different schedule, different cost. Better to know now.
Verifying the engineer
Verify any structural engineer through WA DOL license lookup. Ask for two references on Seattle older-home additions and call both.
Where this information came from
- WA DOL — Engineer license verification · retrieved April 23, 2026