Guide · Tukwila · King County · Updated July 2026
How many units can you build in Tukwila?
If you own or are evaluating a residential lot in Tukwila, the first question is almost always the same: how many homes can legally go on it? Since Washington's HB 1110 middle-housing law took effect, the answer for most Tukwila lots is now more than one. Tukwila's consolidated CR zone allows 3 homes on a standard lot, scaling to 5 on larger lots (or 4 near RapidRide/rail) — above the state Tier 3 floor.
Tukwila at a glance: 3 units per lot by right, up to 5 with the city's bonus, plus up to 2 ADUs under HB 1337. Source: TMC 18.10.040 (Ord. 2765).
What Tukwila's adopted code allows
Tukwila's consolidated CR zone allows 3 homes on a standard lot, scaling to 5 on larger lots (or 4 near RapidRide/rail) — above the state Tier 3 floor. Up to 2 ADUs count toward the maximum.
The details: 4 near a RapidRide stop or rail station (transit/affordability bonus) on smaller lots, then +1 per 1,500 sf of lot area over 5,000 sf, up to 5. These are Tukwila's city-wide standards, per TMC 18.10.040 (Ord. 2765); the exact figure for a specific parcel — its zone, lot size, transit proximity, and critical areas — is what a Civexa report resolves.
What actually fits: floor area, height, and setbacks
HB 1110 and the city code set the right to a number of units; the zone's building envelope sets what physically fits. Floor-area ratio, lot coverage, height, and setbacks together decide whether those homes pencil as detached cottages, a townhouse row, or a stacked-flat building. Civexa computes this envelope for Tukwila zone by zone, so the unit count you see is one the zoning can actually hold.
What can shrink it: critical areas
Steep slopes, wetlands, streams, and flood zones can override the unit math on a specific parcel. A lot that qualifies for the maximum on paper may be constrained once environmentally critical areas are mapped. Civexa screens FEMA flood, slope, and county critical-area layers for every Tukwila address so you find this out before you make an offer, not after.
Get the exact number for your Tukwila parcel
The figures above are Tukwila's city-wide rules. The number that matters is the one for your address — its zone, lot size, transit proximity, and critical areas. Civexa turns that into a full feasibility report in about a minute: unit count, buildable envelope, a preliminary pro forma, utilities, and permit path.
Run a Tukwila feasibility report →
Frequently asked
How many units can I build on a residential lot in Tukwila?
Tukwila's consolidated CR zone allows 3 homes on a standard lot, scaling to 5 on larger lots (or 4 near RapidRide/rail) — above the state Tier 3 floor. That is per TMC 18.10.040 (Ord. 2765). The exact number for a specific parcel still depends on its zone, lot size, transit proximity, and critical areas — run a Civexa report for the parcel-level figure.
Can I add ADUs on top of that in Tukwila?
Washington's HB 1337 allows up to two accessory dwelling units on a residential lot. In some cities they count toward the middle-housing total and in others they are separate — your Civexa report applies Tukwila's specific rule.
What unlocks the maximum in Tukwila?
4 near a RapidRide stop or rail station (transit/affordability bonus) on smaller lots, then +1 per 1,500 sf of lot area over 5,000 sf, up to 5.