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Key takeaways
- Second stories run roughly $350 to $550 per square foot in the Seattle market, and up to $800 on complex high finish work.
- A full second story commonly lands between $250,000 and $600,000.
- Foundation and shear wall upgrades add $30,000 to $100,000 on most pre-1980 Eastside houses.
- Going up preserves yard and lot coverage, which is often the deciding factor on tight Kirkland lots.
- Plan to move out for a full second story. The roof comes off.
This is the question I get asked more than any other on the Eastside, and the honest answer is that it depends on one thing most homeowners never think about: what is under your house.
A second story addition in the Seattle market runs roughly $350 to $550 per square foot of new space, and complex projects with high finish levels reach $800. A full second floor commonly lands between $250,000 and $600,000. Those are market ranges, not a quote.
What a second story actually costs here
| Scope | Typical range, Seattle metro 2026 |
|---|---|
| Partial second story, 400 to 700 sq ft | $180,000 to $360,000 |
| Full second story, 900 to 1,400 sq ft | $320,000 to $600,000+ |
| Structural and foundation upgrades | $30,000 to $100,000 |
| Architect design fee | 12 to 20% of construction |
Ranges reflect published Seattle-area market data for 2026. Your number depends on the existing structure, the finish level and the jurisdiction.
The foundation question that decides everything
Most Eastside houses built before 1980 were not framed to carry another floor. Before anyone draws a plan, the real question is whether your footings, shear walls and point loads can take the load, or what it costs to make them.
- Footings often need to be widened or deepened where new posts land.
- Shear walls get added or upgraded to meet current seismic code.
- A new beam line usually has to carry down through the main floor to the foundation.
- Older framing frequently does not match the original drawings, so we verify in the field.
This is why I will not quote a second story from a photograph. A one hour walk of the house tells us more than a week of guessing.
Free consultation
Find out in one conversation whether your house can go up
A 30 minute call with David, the architect who would design it. No obligation, no pitch. You will leave knowing the likely structural path and a realistic budget band.
Going up against going out
Going out is usually cheaper per square foot, because you are building on new footings without touching the existing structure. Going up preserves yard, keeps you inside your lot coverage limit, and on a view lot it buys something an addition on the ground never can.
| Second story | Ground floor addition | |
|---|---|---|
| Cost per sq ft | Higher | Lower |
| Yard and lot coverage | Preserved | Consumed |
| Views | Often gained | Rarely changed |
| Structural risk | Higher | Lower |
| Living through it | Usually move out | Often stay |
On tight Kirkland and Bellevue lots where lot coverage is already close to the limit, up is frequently the only legal direction.
When it is worth it, and when it is not
It is usually worth it when: your lot coverage is maxed out, you would gain a view, the foundation is in decent shape, you plan to stay five or more years, or the alternative is buying a comparable home at Eastside prices plus transaction costs.
It is usually not worth it when: the foundation needs near-total replacement, the roofline forces a design that fights the house, or you only need one more room and a bump-out solves it for a third of the money.
I have talked homeowners out of second stories. If a 300 square foot bump-out gets you what you actually need, that is the advice you will get.
Timeline and living arrangements
Design through permit typically runs 4 to 8 months on the Eastside, and construction another 6 to 12. Kirkland addition permits commonly take 6 to 10 weeks in plan review once the package is complete, submitted through MyBuildingPermit.com.
Plan to move out for most of a full second story. The roof comes off. That is the part nobody tells you early enough.
Talk to the architect
Get a straight answer on your house
Call or message David directly. He will tell you whether going up makes sense before you spend anything on drawings.