DADU feasibility · West Seattle Junction
Building a DADU in West Seattle Junction
The Junction's 6,797 parcels are the most uniform in West Seattle, with 67% at 5,000 sq ft or larger and just 4.4% potential-landslide ground. That consistency is why pre-approved plans fit here more often.
The Junction has the most uniform mid-size lot pattern in West Seattle and comparatively gentle ground. This profile is measured from City of Seattle open data across 6,797 parcels in West Seattle Junction/Genesee Hill — not estimated, and not the same numbers as any other neighborhood on this site.
Lot sizes in West Seattle Junction
An unusually consistent profile: the majority of parcels sit in the 5,000–7,200 sq ft band. That consistency is why pre-approved standard plans fit here more often than in most of West Seattle.
Parcel counts by lot size, West Seattle Junction/Genesee Hill. Source: King County parcels via Seattle's ADUniverse dataset.
33% of parcels here are under 5,000 sq ft and 67% 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 Seattle repealed the old 3,200 sq ft minimum lot area for a DADU, so small lots are no longer excluded; they are simply governed by the floor-area budget instead.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
Moderate steep slope and a modest slide-prone share — far less than the shoreline neighborhoods to the west and south. The plateau around the Junction is genuinely buildable ground.
West Seattle Junction 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
7.5% of West Seattle Junction is mapped as steep slope (40% or greater) and 4.4% 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
Side sewer, water and electrical capacity
35% of buildings here predate 1940 and 33% 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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03
Protected trees
Tree canopy covers 24.6% of West Seattle Junction (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.
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04
Physical fit on a small lot
33% 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
Liquefaction and soil conditions
2.8% of West Seattle Junction 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.
Zoning and utilities
Zoning mix
- SF 50005,069 parcels
- RSL336 parcels
- LR2326 parcels
- LR1188 parcels
- SF 7200134 parcels
81.5% of parcels are Neighborhood Residential or Residential Small Lot; 11.3% 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 194035%
- 1940 – 197533%
- After 197529%
Mid-century stock with reasonable utility runs. The practical constraint is often the existing house's position on the lot rather than the site itself.
West Seattle Junction DADU questions
Can I build a DADU in West Seattle Junction?
In almost all cases the zoning allows it. 81.5% of parcels in West Seattle Junction 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 West Seattle Junction?
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. 67% of West Seattle Junction 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 West Seattle Junction?
Slope and landslide-prone ground — 7.5% of West Seattle Junction is mapped as steep slope (40% or greater) and 4.4% 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 West Seattle Junction
Free, written for Seattle's code, and picked from West Seattle Junction'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 West Seattle Junction.
This page tells you what West Seattle Junction 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.