How Seattle's FAR and Lot Coverage Rules Work

Floor area ratio and lot coverage are the two zoning controls that determine how much building fits on a lot. Height limits get more attention, but FAR and lot coverage are what actually constrain the number of units you can build. If you're evaluating a multi-family site in Seattle, these numbers drive feasibility.

Floor Area Ratio (FAR)

FAR is the ratio of total building floor area to lot area. A 5,000-square-foot lot with a FAR of 3.0 allows up to 15,000 square feet of floor area. That floor area can be distributed across however many stories the height limit allows.

FAR varies by zone:

Zone	Typical FAR	What it allows
LR1	1.0 to 1.3	Small apartments, townhomes
LR2	1.1 to 1.6	Mid-density apartment buildings
LR3	1.2 to 2.3	Larger apartment buildings
MR	3.2 to 4.5	Midrise apartments
NC2-65	4.25 to 4.75	Mixed-use, 5 to 6 stories
NC3-85	5.0 to 5.75	Mixed-use, 7 to 8 stories
HR	No fixed FAR	Governed by tower floor plate and other controls

These numbers shift depending on whether the project uses incentive zoning (providing affordable units or paying into the affordable housing fund in exchange for bonus floor area).

FAR Bonuses

Seattle's incentive zoning program (Mandatory Housing Affordability, or MHA) grants additional FAR when developers include affordable units or pay a fee. The bonus can add 20 to 40 percent above the base FAR depending on the zone. In practice, almost every new multi-family project in Seattle uses MHA bonuses because the base FAR alone makes many projects financially unworkable.

Lot Coverage

Lot coverage limits how much of the lot a building's footprint can occupy, measured as a percentage of lot area.

Zone	Max lot coverage
LR1	50 to 60%
LR2	60 to 65%
LR3	65 to 75%
MR	75 to 85%
NC	80 to 100%

In lowrise zones, lot coverage is the binding constraint on many sites. A 5,000-square-foot LR2 lot with 60% coverage means a maximum footprint of 3,000 square feet. At three stories, that gives you 9,000 square feet of floor area, which translates to roughly 10 to 12 apartments depending on unit size.

NC zones allow up to 100% lot coverage, meaning the building can fill the entire lot. That's why mixed-use buildings on arterials are built lot line to lot line.

How FAR and Lot Coverage Interact

These two controls work together, and one is usually more restrictive than the other depending on the zone.

In LR zones, lot coverage is often the tighter constraint. You might have enough FAR for more floor area, but the lot coverage limit restricts your footprint, which limits how many units you can fit per floor.

In NC and MR zones, FAR is usually the binding constraint. You can cover most or all of the lot, but FAR caps the total floor area you can stack on it.

When evaluating a site, calculate both numbers. The lower one sets your maximum building size.

How the One Seattle Plan Changes This

The One Seattle Plan simplifies midrise zoning standards and increases FAR in several zone categories. The old MR zones had a four-story effective cap because FAR was too low to justify a five-story building. The new standards raise the FAR enough to make five to seven story apartment buildings pencil in MR zones.

For properties rezoned from SF to LR under the new Neighborhood Centers, the shift from a single-family FAR (around 0.5) to an LR FAR (1.0 to 2.3) represents a major increase in development capacity.

Checking FAR and Lot Coverage

You can look up the zoning designation for any parcel on the Seattle GIS map, then check the corresponding FAR and lot coverage limits in the Seattle Municipal Code (Title 23). On BuildVue, each project page shows the zoning designation alongside the project's permits and development details.