DADU feasibility · Beacon Hill
Building a DADU in Beacon Hill
Beacon Hill's 3,449 parcels are 88.9% detached houses with just 16.4% tree canopy — the cleanest combination measured anywhere in this set. Only 8.0% is steep slope, confined to the ridge edges.
Beacon Hill has the highest detached-house share of any area in this set and the lightest tree canopy — an unusually clean combination for a cottage. This profile is measured from City of Seattle open data across 3,449 parcels in Beacon Hill — not estimated, and not the same numbers as any other neighborhood on this site.
Lot sizes in Beacon Hill
Lots are solidly mid-size, with most above 5,000 sq ft. Combined with a housing stock that is nearly nine-tenths detached single houses, the typical Beacon Hill parcel is a straightforward DADU candidate on geometry alone.
Parcel counts by lot size, Beacon Hill. Source: King County parcels via Seattle's ADUniverse dataset.
32% of parcels here are under 5,000 sq ft and 68% 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 Seattle repealed the old 3,200 sq ft minimum lot area for a DADU, so small lots are no longer excluded; they are simply governed by the floor-area budget instead.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 ridge line carries steep slope along its edges, but the plateau is stable and there is essentially no mapped landslide-prone ground. Canopy is the lowest in this set, which means fewer Tier 2 and Tier 3 tree conflicts than almost anywhere else in Seattle.
Beacon Hill 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
Side sewer, water and electrical capacity
19% of buildings here predate 1940 and 43% 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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02
Slope and landslide-prone ground
8% of Beacon Hill is mapped as steep slope (40% or greater) and 0% 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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03
Liquefaction and soil conditions
7.8% of Beacon Hill 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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04
Physical fit on a small lot
32% 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 16.4% of Beacon Hill (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 50002,727 parcels
- SF 7200260 parcels
- LR2120 parcels
- LR389 parcels
- MR71 parcels
88.2% of parcels are Neighborhood Residential or Residential Small Lot; 7.4% 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 194019%
- 1940 – 197543%
- After 197528%
Mid-century stock on a ridge. Confirm panel capacity; the sewer runs are generally shorter and simpler than the north end's deep lots.
Beacon Hill DADU questions
Can I build a DADU in Beacon Hill?
In almost all cases the zoning allows it. 88.2% of parcels in Beacon Hill 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 Beacon Hill?
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. 68% of Beacon Hill 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 Beacon Hill?
Side sewer, water and electrical capacity — 19% of buildings here predate 1940 and 43% 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.
Read these before you spend anything on Beacon Hill
Free, written for Seattle's code, and picked from Beacon Hill'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 Beacon Hill.
This page tells you what Beacon Hill 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.