Guide · Federal Way · King County · Updated July 2026
How many units can you build in Federal Way?
If you own or are evaluating a residential lot in Federal Way, 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 Federal Way lots is now more than one. Federal Way allows 4 units per lot by right on RS lots, rising to 6 near frequent transit or with two affordable units.
Federal Way at a glance: 4 units per lot by right, up to 6 with the city's bonus, plus up to 2 ADUs under HB 1337. Source: FWRC 19.195/19.200 (Ord. 25-1016).
What Federal Way's adopted code allows
Federal Way allows 4 units per lot by right on RS lots, rising to 6 near frequent transit or with two affordable units. Septic-only lots may be limited to 2 units.
The details: 6 near a major transit stop or with at least two affordable units. These are Federal Way's city-wide standards, per FWRC 19.195/19.200 (Ord. 25-1016); 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 Federal Way 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 Federal Way address so you find this out before you make an offer, not after.
Get the exact number for your Federal Way parcel
The figures above are Federal Way'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 Federal Way feasibility report →
Frequently asked
How many units can I build on a residential lot in Federal Way?
Federal Way allows 4 units per lot by right on RS lots, rising to 6 near frequent transit or with two affordable units. That is per FWRC 19.195/19.200 (Ord. 25-1016). 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 Federal Way?
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 Federal Way's specific rule.
What unlocks the maximum in Federal Way?
6 near a major transit stop or with at least two affordable units.