DADU feasibility · Alki & Admiral
Building a DADU in Alki & Admiral
Alki and Admiral carry the hardest site constraints measured anywhere: 22.3% steep slope and 30.1% potential landslide across 3,862 parcels. Near the bluff, a geotechnical report decides whether a project exists at all.
Alki and Admiral carry the most difficult site constraints of any area in this set — the bluff runs through the middle of the market. This profile is measured from City of Seattle open data across 3,862 parcels in Alki/Admiral — not estimated, and not the same numbers as any other neighborhood on this site.
Lot sizes in Alki & Admiral
Lot sizes vary widely, from sub-3,200 beach platting to large lots above 10,000. Geometry is rarely the deciding factor here; the ground is.
Parcel counts by lot size, Alki/Admiral. Source: King County parcels via Seattle's ADUniverse dataset.
43% of parcels here are under 5,000 sq ft and 57% are 5,000 sq ft or larger — a middling share among the 18 areas profiled here. Seattle repealed the old 3,200 sq ft minimum lot area for a DADU, so small lots are no longer excluded; they are simply governed by the floor-area budget instead.
What the ground looks like
This is the most constrained area measured: the highest steep-slope share in the set, nearly a third mapped as potential landslide area, and the highest share of known historical landslide ground. A geotechnical report is not optional near the bluff — it shapes whether a project exists at all.
Alki & Admiral against the median of the 18 Seattle areas profiled here. Hazard layers clipped to the neighborhood boundary; canopy is area-weighted by census block group.
What decides feasibility here, in order
Ranked by what this neighborhood's own measurements say — not a generic checklist.
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01
Slope and landslide-prone ground
22.3% of Alki & Admiral is mapped as steep slope (40% or greater) and 30.1% as potential landslide area, against Seattle medians of 7.7% and 4.4% across the areas profiled here. Land inside an Environmentally Critical Area under SMC 25.09 triggers additional review and, in practice, a geotechnical report before design.
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02
Liquefaction and soil conditions
25.8% of Alki & Admiral sits on mapped liquefaction-prone soils (Seattle median here: 8.7%). This rarely stops a project, but it changes foundation design and belongs in the budget before you price a build.
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03
Side sewer, water and electrical capacity
27% of buildings here predate 1940 and 25% were built between 1940 and 1975. Older stock means older side sewers and smaller electrical services — the two utility findings that most often reset a DADU budget.
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04
Physical fit on a small lot
43% of parcels here are under 5,000 sq ft. Lot size no longer disqualifies a DADU, but on a tight lot the lot-wide FAR and lot-coverage budget — which ADU floor area now counts toward — usually binds before setbacks do.
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05
Protected trees
Tree canopy covers 24.9% of Alki & Admiral (Seattle median here: 26.9%). Seattle's tree code (SMC 25.11) protects trees by tier, and a Tier 2 tree with its root protection area falling across your rear yard can move or shrink a cottage even on a large lot.
Zoning and utilities
Zoning mix
- SF 50002,201 parcels
- SF 7200492 parcels
- LR1426 parcels
- LR3294 parcels
- LR2251 parcels
70.5% of parcels are Neighborhood Residential or Residential Small Lot; 25.3% are Lowrise. Zone labels reflect the parcel dataset's legacy single-family categories, which map into today's Neighborhood Residential zone under Ordinance 127376.
Housing age
- Before 194027%
- 1940 – 197525%
- After 197539%
Older shoreline stock, long utility runs, and access routes that are frequently the binding constraint. Expect the geotech and access questions to be answered before any design work begins.
Alki & Admiral DADU questions
Can I build a DADU in Alki & Admiral?
In almost all cases the zoning allows it. 70.5% of parcels in Alki & Admiral sit in Neighborhood Residential or Residential Small Lot zoning, where detached accessory dwelling units are permitted, and Seattle removed both the old minimum-lot-size test and the owner-occupancy requirement. The real question is whether a compliant cottage physically fits your lot and whether utilities can serve it.
How big can a DADU be in Alki & Admiral?
The citywide caps apply: 1,000 sq ft of gross floor area for an ADU with up to two bedrooms, or 1,200 sq ft with three or more. On top of that, your lot has a single FAR and lot-coverage budget shared with the existing house — which is what actually limits most projects. 57% of Alki & Admiral parcels are 5,000 sq ft or larger, so whether you reach the cap depends heavily on which block you are on.
What is most likely to block a DADU in Alki & Admiral?
Slope and landslide-prone ground — 22.3% of Alki & Admiral is mapped as steep slope (40% or greater) and 30.1% as potential landslide area, against Seattle medians of 7.7% and 4.4% across the areas profiled here. Land inside an Environmentally Critical Area under SMC 25.09 triggers additional review and, in practice, a geotechnical report before design.
Read these before you spend anything on Alki & Admiral
Free, written for Seattle's code, and picked from Alki & Admiral's own numbers rather than a generic list.
All 20 guides and notes → · every record we can read on a Seattle parcel →
Next step
Get the report for your address in Alki & Admiral.
This page tells you what Alki & Admiral looks like as a whole. The customized feasibility report runs your specific address through the same review — setbacks and FAR headroom, tree tiers, mapped critical areas, side sewer and panel capacity, and a permit path — measured from City records and reviewed by a person. Prefer to self-study? The Pro Guide covers the same rules.