Guide · Seattle · Updated June 2026

How many homes can you build on a Seattle lot?

A practical 2026 guide to unit counts, floor-area ratio, and middle housing under HB 1110 and Seattle's Neighborhood Residential code.

If you own — or are eyeing — a residential lot in Seattle, the first question is almost always the same: how many homes can legally go on it? Thanks to Washington's HB 1110 and Seattle's updated zoning, the answer for most lots is now more than one. Here's how it actually works.

The baseline: four to six units on most residential lots

Seattle, as a Tier 1 city under HB 1110, must allow at least four units on most residential lots. Lots within a quarter-mile walking distance of a major transit stop — light rail or RapidRide bus rapid transit — can reach six units. A lot can also reach six units if at least two of them are income-restricted affordable housing.

What actually fits: floor-area ratio (FAR)

The unit count is only half the story. How much building you can put on the lot is governed by floor-area ratio — the ratio of total building floor area to lot area. Seattle sets FAR by density: the more units per square foot of lot, the higher the FAR allowance, up to roughly 1.6 for the densest configurations (and higher for stacked apartments).

In practice, that means a typical 5,000-square-foot lot can support several thousand square feet of buildable floor area — enough for marketable townhomes or a small multiplex, not the tiny units a naive "divide the lot evenly" estimate would suggest.

What can shrink it: critical areas

Environmentally critical areas — steep slopes, liquefaction-prone soils, landslide zones, wetlands — reduce both how much you can build and how much it costs. A steep slope can cut usable lot area significantly and add expensive structural requirements like retaining walls and deep foundations. Always check a lot's critical-area status before underwriting.

Parking, height, and setbacks

• Parking: none is required within a half-mile of frequent transit; otherwise roughly one space per unit.
• Height: 32 feet base, up to 42 feet for developments of three or more units that meet form requirements — enough for three stories.
• Setbacks: generally smaller for middle-housing developments than for traditional single-family homes, which helps fit more building on the lot.

The bottom line

For most Seattle residential lots in 2026, the realistic answer is four to six homes, with the exact number and buildable size driven by transit access, lot size, and any critical-area constraints. The only way to know your lot's specific number is to run it against the actual code.