Guide · Des Moines · King County · Updated July 2026
How many units can you build in Des Moines?
If you own or are evaluating a residential lot in Des Moines, 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 Des Moines lots is now more than one. Des Moines allows the greater of 4 units per lot or 24 homes per acre on all residential zones, with no separate transit or affordability tier.
Des Moines at a glance: at least 4 units per lot, with more allowed by lot size and zoned density, plus up to 2 ADUs under HB 1337. Source: DMMC 18.57 (Ord. 1821).
What Des Moines's adopted code allows
Des Moines allows the greater of 4 units per lot or 24 homes per acre on all residential zones, with no separate transit or affordability tier. ADUs count toward the total (up to 3).
The details: no separate transit tier — the uniform rule is the greater of 4 units per lot or 24 homes per acre, so larger lots exceed 4. These are Des Moines's city-wide standards, per DMMC 18.57 (Ord. 1821); 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 Des Moines 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 Des Moines address so you find this out before you make an offer, not after.
Get the exact number for your Des Moines parcel
The figures above are Des Moines'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 Des Moines feasibility report →
Frequently asked
How many units can I build on a residential lot in Des Moines?
Des Moines allows the greater of 4 units per lot or 24 homes per acre on all residential zones, with no separate transit or affordability tier. That is per DMMC 18.57 (Ord. 1821). 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 Des Moines?
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 Des Moines's specific rule.
What unlocks the maximum in Des Moines?
No separate transit tier — the uniform rule is the greater of 4 units per lot or 24 homes per acre, so larger lots exceed 4.