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Key takeaways
- A bedroom addition without a bathroom commonly runs $85,000 to $165,000 on the Eastside.
- A primary suite with a bathroom runs $220,000 to $400,000.
- Adding one plumbing group is the single biggest jump in any room addition.
- Kirkland addition permits commonly take 6 to 10 weeks in plan review with a complete package.
- If 60 to 140 square feet solves it, a bump-out can cost half as much.
A room addition is the most common project I take on in Kirkland. It is also the one where quotes vary most wildly, because “a room” can mean 180 square feet off the back or a 450 square foot primary suite with a bathroom and a new roof line.
Cost by room type
| Room | Typical size | Range, Eastside 2026 |
|---|---|---|
| Bedroom, no bathroom | 180 to 250 sq ft | $85,000 to $165,000 |
| Family or great room | 300 to 450 sq ft | $150,000 to $290,000 |
| Primary suite with bathroom | 350 to 500 sq ft | $220,000 to $400,000 |
| Home office, conditioned | 140 to 200 sq ft | $70,000 to $140,000 |
| Kitchen bump-out | 60 to 140 sq ft | $55,000 to $130,000 |
Ranges are for planning on the Eastside in 2026 and are not a quote. Seattle-area construction runs 25 to 40 percent above national averages, partly because Washington charges sales tax on labor as well as materials.
Where the money actually goes
- Foundation and site. New footings, drainage and any slope work. On a sloped Kirkland lot this alone can move the budget 15 percent.
- Roof tie-in. Matching pitch and flashing into an existing roof is fussy work and it is where leaks start if it is drawn badly.
- Mechanical reach. Whether your existing furnace and panel can serve the new space, or need upgrading.
- Bathrooms. Adding one plumbing group is the single biggest jump in any room addition.
- Finish level. The same 300 square feet can be $150,000 or $290,000 purely on materials.
Free consultation
Get a real range for your specific room
Tell David the room, the wall it comes off and roughly the size. He will give you a realistic band on the call, before anyone draws anything.
Kirkland permit reality
Kirkland addition permits commonly run 6 to 10 weeks in plan review when the package is complete, submitted through MyBuildingPermit.com. Incomplete packages are the main reason projects stall, not city slowness.
Your parcel sits in an RSA or RMA zone with its own setback, lot coverage and height rules. If you are near Lake Washington, Forbes Creek or North Creek, shoreline or critical areas review can apply on top. We check the parcel before design, not after.
When a bump-out beats an addition
If you need 60 to 140 square feet in the right place, a bump-out is often half the cost of a full addition because it can cantilever off existing framing with no new foundation. Kitchens and dining areas are the usual candidates.
If a bump-out solves your problem, I will tell you that on the first call. It is a smaller fee for me and the right answer for you.
Talk to David
One call, one honest number
Call 425 753 6452 or WhatsApp. Free 30 minute consultation with the architect who would design it.