Guide · Mukilteo · Snohomish County · Updated July 2026
How many units can you build in Mukilteo?
If you own or are evaluating a residential lot in Mukilteo, 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 Mukilteo lots is now more than one. Mukilteo allows a flat 2 units per lot, achievable with ADUs, duplexes, or cottage housing.
Mukilteo at a glance: 2 units per lot — a flat allowance, no transit or affordability bonus tier, plus up to 2 ADUs under HB 1337. Source: MMC 17.12 (Ord. 1516).
What Mukilteo's adopted code allows
Mukilteo allows a flat 2 units per lot, achievable with ADUs, duplexes, or cottage housing.
The details: none — a flat 2 units per lot; no transit or affordability tier. These are Mukilteo's city-wide standards, per MMC 17.12 (Ord. 1516); 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 Mukilteo 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 Mukilteo address so you find this out before you make an offer, not after.
Get the exact number for your Mukilteo parcel
The figures above are Mukilteo'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 Mukilteo feasibility report →
Frequently asked
How many units can I build on a residential lot in Mukilteo?
Mukilteo allows a flat 2 units per lot, achievable with ADUs, duplexes, or cottage housing. That is per MMC 17.12 (Ord. 1516). 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 Mukilteo?
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 Mukilteo's specific rule.
What unlocks the maximum in Mukilteo?
None — a flat 2 units per lot; no transit or affordability tier.