DADU feasibility · Wallingford
Building a DADU in Wallingford
Three-quarters of Wallingford's 4,343 parcels are under 5,000 sq ft, and just 1.9% are mapped as steep slope. It is the tightest-lot, flattest-ground combination in this set.
Wallingford has the tightest lots of any established north-end DADU market, and the flattest ground to build them on. This profile is measured from City of Seattle open data across 4,343 parcels in Wallingford — not estimated, and not the same numbers as any other neighborhood on this site.
Lot sizes in Wallingford
Three quarters of Wallingford's parcels are under 5,000 sq ft, and a large share are under 3,200. Lot size no longer disqualifies a DADU, but at this scale the lot-wide FAR budget is almost always what binds — especially with a two-storey house already using most of it.
Parcel counts by lot size, Wallingford. Source: King County parcels via Seattle's ADUniverse dataset.
76% of parcels here are under 5,000 sq ft and 24% are 5,000 sq ft or larger — a low 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 Seattle repealed the old 3,200 sq ft minimum lot area for a DADU, so small lots are no longer excluded; they are simply governed by the floor-area budget instead.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
Wallingford is flat and stable: the lowest steep-slope and landslide exposure in this set. There is essentially no geotechnical story here, which is rare in Seattle and genuinely simplifies the risk review.
Wallingford 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
65% of buildings here predate 1940 and 4% 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
Physical fit on a small lot
76% 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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03
Protected trees
Tree canopy covers 23.1% of Wallingford (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
Slope and landslide-prone ground
1.9% of Wallingford 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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05
Liquefaction and soil conditions
1.4% of Wallingford 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 50002,549 parcels
- LR2569 parcels
- LR1467 parcels
- MR219 parcels
- NC2P-55110 parcels
60.2% of parcels are Neighborhood Residential or Residential Small Lot; 26.5% 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 194065%
- 1940 – 19754%
- After 197528%
The stock skews early — a lot of 1900s–1930s houses on original side sewers. Wallingford is a neighborhood where the camera inspection is worth doing before the design fee, not after.
Wallingford DADU questions
Can I build a DADU in Wallingford?
In almost all cases the zoning allows it. 60.2% of parcels in Wallingford 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 Wallingford?
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 76% of Wallingford parcels under 5,000 sq ft, the cap is usually academic here — the lot-wide budget runs out first, and a 600–800 sq ft cottage is the realistic target.
What is most likely to block a DADU in Wallingford?
Side sewer, water and electrical capacity — 65% of buildings here predate 1940 and 4% 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 Wallingford
Free, written for Seattle's code, and picked from Wallingford'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 Wallingford.
This page tells you what Wallingford 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.