DADU feasibility · Magnolia
Building a DADU in Magnolia
Magnolia's 5,245 parcels are among the largest measured, with 77% at 5,000 sq ft or more and 78.8% detached homes. But 13.5% steep slope and 16.2% potential-landslide mapping put the bluff at the center of almost every decision.
Magnolia has the largest lots and the highest owner-occupancy on this list, and a bluff that decides a meaningful share of projects. This profile is measured from City of Seattle open data across 5,245 parcels in Magnolia — not estimated, and not the same numbers as any other neighborhood on this site.
Lot sizes in Magnolia
Lot geometry is excellent — the great majority sit above 5,000 sq ft and a large share above 7,200. On the interior of the peninsula, physical fit is rarely the issue.
Parcel counts by lot size, Magnolia. Source: King County parcels via Seattle's ADUniverse dataset.
23% of parcels here are under 5,000 sq ft and 77% are 5,000 sq ft or larger — a high 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 Seattle repealed the old 3,200 sq ft minimum lot area for a DADU, so small lots are no longer excluded; they are simply governed by the floor-area budget instead.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
The bluff is the story. A significant share of Magnolia is mapped steep slope, and more is potential landslide area, with known historical slides along the western and southern edges. A lot near the bluff needs a geotech report before any design money is spent.
Magnolia 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
13.5% of Magnolia is mapped as steep slope (40% or greater) and 16.2% 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
25% of buildings here predate 1940 and 45% 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 33.5% of Magnolia (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
23% 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
3.7% of Magnolia 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 50004,199 parcels
- SF 7200647 parcels
- LR1103 parcels
- SF 960079 parcels
- LR3 RC70 parcels
93.9% of parcels are Neighborhood Residential or Residential Small Lot; 3.8% 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 194025%
- 1940 – 197545%
- After 197527%
Older, larger homes on long runs to the street. Trenching distance and slope both push utility connection costs above the citywide norm.
Magnolia DADU questions
Can I build a DADU in Magnolia?
In almost all cases the zoning allows it. 93.9% of parcels in Magnolia 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 Magnolia?
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. With 77% of Magnolia parcels at 5,000 sq ft or larger, most owners here have room to reach the cap rather than being cut off by it.
What is most likely to block a DADU in Magnolia?
Slope and landslide-prone ground — 13.5% of Magnolia is mapped as steep slope (40% or greater) and 16.2% 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 Magnolia
Free, written for Seattle's code, and picked from Magnolia'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 Magnolia.
This page tells you what Magnolia 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.