Architects are quoting all over the map. What’s a fair design fee?

Question

Marcus Golen · Accepted Answer

For a custom DADU in Seattle, design + structural + civil + energy modeling typically runs $22–38k (roughly 6–8% of construction cost). Pre-approved plans drop that to $8–14k (site adaptation only). Beware quotes under $15k for custom — they usually exclude structural calcs, energy compliance, or revisions, all of which become change orders. A solid design package includes: architectural set, structural set, civil/site, energy compliance form, MEP narrative, and 2 rounds of revision included.

Answer

For a fully detached, code-built DADU in Seattle (2026), realistic all-in pricing is $340k–$520k for 600–1,000 sqft. That includes design ($18–35k), SDCI permit fees ($14–22k), site work and utility runs ($30–70k), construction ($240–380k), and a 10–15% contingency. Quotes under $250k almost always exclude utility sepa

Answer

AADU wins on upfront cost (typically $180–$300k for a basement conversion) but rents for 15–25% less and is harder to refinance separately. DADU costs more ($340–$520k) but commands premium rent ($2,400–$3,400/mo in Seattle), is easier to refinance with separate utility meters, and adds more resale value. ROI math: a D

Answer

In 2026, a new 600–800 sqft DADU in core Seattle (Ballard, Capitol Hill, Wallingford, West Seattle) rents for $2,400–$3,200/mo unfurnished and $3,200–$4,500/mo furnished/short-term. North Seattle (Lake City, Northgate) is 10–15% lower. Outside Seattle, expect Bellevue $2,600–$3,400, Kirkland $2,400–$3,100, Redmond $2,5

Answer

Detached garage-to-DADU conversion in Seattle typically runs $220–$340k for 400–600 sqft. The garage shell saves you ~$40–60k versus ground-up but you almost always need new foundation work (most garages don’t meet residential code), full insulation, new electrical service, water/sewer extensions, and full Energy Code

Answer

Recent (2024–2026) Seattle appraisal data shows DADUs add 65–85% of build cost to appraised value at first appraisal — so a $400k DADU adds roughly $260–340k. Within 3–5 years, as comps mature, that ratio rises to 85–110%. AADUs add less in absolute dollars but a higher ratio (~90% of cost) because they don’t require n

Answer

Expect your property tax bill to increase by $3,500–$6,500/year for a typical $400k DADU in Seattle (King County’s effective rate is roughly 0.85–1.05%). That’s a real expense to underwrite — at $5k/year, it eats ~14% of typical DADU rental income. Reassessment usually happens 6–18 months after final inspection. Plan f

How much should I budget for ADU design and architecture?

Free 30-min consult with a licensed ADU PM

Frequently asked

Is this answer about "How much should I budget for ADU design and architecture?" specific to my situation?

Can I submit a follow-up question?

How do I trust the answer to "How much should I budget for ADU design and architecture?" is current?

Where do I go after reading the answer to "How much should I budget for ADU design and architecture?"?

Continue exploring the Puget Sound build map

Got this question about YOUR lot? Send the specifics — answer in 24h.