Key takeaways
- Most single-family lots in Kirkland are zoned RS, RSX or RSA. In RS and RSX the number is the minimum lot size in thousands of square feet (RS 7.2 means 7,200). In RSA it is homes per acre.
- RS and RSX look alike but build differently. RS needs side yards that add up to 15 feet and caps height at 25 feet above average building elevation. RSX needs 5 feet a side and allows 30 feet.
- Floor area is capped as a share of the lot: 50 percent in most zones, 35 percent in the 12.5 zones and 20 percent in the 35 zones and RSA 1. Rooms taller than 16 feet count double.
- Lot coverage is 50 percent in most zones, and it counts the driveway, patio and walks along with the house.
- Within 200 feet of Lake Washington the shoreline chapter adds its own setback from the water, and the middle housing rules do not apply there.
Short answer: on a typical Kirkland single-family lot you can build one house, plus up to two accessory dwelling units, as long as it fits inside your zone’s yards, a floor area cap written as a percentage of the lot, lot coverage that counts paving as well as roof, and a height limit measured from the average grade around the house.
For how I work here, see my Kirkland architect page. Every code figure below comes from the Kirkland Zoning Code (KZC), current through Ordinance 4947 of September 1, 2026, or the city’s own zoning pages. Figures are as of September 2026, so confirm with the city before you rely on any number.
Kirkland’s single-family zones: RS, RSX and RSA
Chapter 15 of the zoning code, Low Density Residential Zones, covers the city’s low density residential zones: RS 35, 12.5, 8.5, 7.2, 6.3 and 5.0; RSX 35, 12.5, 8.5, 7.2 and 5.0; RSA 1, 4, 6 and 8; and a few special zones (WD II, PLA 3C, PLA 6E, PLA 16). There is no separate RSX or RSA chapter in the current code: Ordinance 4476 (2015) repealed the old Chapters 17 and 18 and replaced Chapter 15. They all share the density and dimensions table in KZC 15.30.
In RS and RSX zones the number is the minimum lot size in thousands of square feet, so RS 8.5 means 8,500 square feet. RSA works differently. The number is the maximum homes per acre, and RSA 4, 6 and 8 each have their own minimum lot (7,600 square feet in RSA 4, for example). Only one house is allowed per lot, whatever its size, unless the project uses the middle housing rules. KZC 115.07 also allows two accessory dwelling units, attached or detached; see my Kirkland ADU guide.
In the permitted uses table (KZC 15.20), the review process for a detached house reads “None.” There is no land use hearing; zoning is checked inside the building permit review.
How to find your zone
The city’s Zoning Code FAQ gives the quickest route. Open Kirkland Maps, click the Task tab, then the Address button, and enter your address. Clicking the Parcel and Permit History link shows the zoning, and the Parcel Zoning link takes you to the matching part of the online code. The city also posts a citywide zoning map as a PDF.
Look for overlays too. The Holmes Point (Chapter 70) and Goat Hill (Chapter 71) overlays add rules, and a lot within 200 feet of Lake Washington also falls under the shoreline chapter (Chapter 83). Read every numbered special regulation, and the general regulations too.
The core numbers, zone by zone
These are the standards for a detached house in the three zone families.
| Zone | Front yard | Side yards | Rear yard | Max lot coverage | Max height |
|---|---|---|---|---|---|
| RS (35, 12.5, 8.5, 7.2, 6.3, 5.0) | 20 ft | 5 ft each, 15 ft combined | 10 ft | 50% | 25 ft above ABE |
| RSX (35, 12.5, 8.5, 7.2, 5.0) | 20 ft | 5 ft each | 10 ft | 50% | 30 ft above ABE |
| RSA (1, 4, 6, 8) | 20 ft | 5 ft each | 10 ft | 50% (30% in RSA 1) | 30 ft above ABE |
Source: KZC 15.30.060 with special regulations DD-6 and DD-9. ABE is average building elevation. RSA lots in the Juanita Beach Camps and Carr’s Park plats get 35 feet (DD-21).
The floor area cap, called F.A.R. (floor area ratio), is set zone by zone:
| Zone | Minimum lot size | Maximum F.A.R. |
|---|---|---|
| RS 35 and RSX 35 | 35,000 sq ft | 20% of the lot |
| RS 12.5 and RSX 12.5 | 12,500 sq ft | 35% of the lot |
| RS 8.5 and RSX 8.5 | 8,500 sq ft | 50% of the lot |
| RS 7.2 and RSX 7.2 | 7,200 sq ft | 50% of the lot |
| RS 6.3 | 6,300 sq ft | 50% of the lot |
| RS 5.0 and RSX 5.0 | 5,000 sq ft | 50%, or up to 60% on the first 5,000 sq ft with center-peaked roofs and 7.5 ft side yards |
| RSA 1 | Clustered lots, 1 home per acre | 20% of the lot |
| RSA 4 | 7,600 sq ft, 4 homes per acre | 50% of the lot |
| RSA 6 | 5,100 sq ft, 6 homes per acre | 50% of the lot |
| RSA 8 | 3,800 sq ft, 8 homes per acre | 50%, or up to 60% on the first 5,000 sq ft with center-peaked roofs |
Source: KZC 15.30 special regulations DD-7, DD-11, DD-12, DD-17 and DD-19. In RSA zones, F.A.R. does not apply to property inside the shoreline jurisdiction.
Two examples. A 10,000 square foot RS 8.5 lot can carry 5,000 square feet of floor area (10,000 x 0.50), and 5,000 square feet of footprint, driveway and patio combined. A 40,000 square foot RSX 35 lot is held to 8,000 square feet of floor area (40,000 x 0.20) while coverage would allow 20,000.
Setbacks, and the 15 foot rule in RS zones
- Front yard. 20 feet in RS, RSX and RSA. On a corner lot in RSX or RSA, only one front yard has to be 20 feet and the others are treated as 5 foot side yards.
- Side yards. In RS, each side is at least 5 feet and the two must add up to at least 15 feet. RSX and RSA need 5 feet on each side, with no combined total. On a 60 foot wide lot that is the difference between a 45 foot wide house (60 minus 15) and a 50 foot wide one (60 minus 10).
- Rear yard. 10 feet.
What can sit in the yards (KZC 115.115): eaves, chimneys and bay windows may project 18 inches into a yard, but chimneys and bay windows may come no closer than 4 feet to a property line, and a one-story covered entry porch open on three sides can come to 13 feet from the front line. A front yard driveway is generally limited to 20 feet wide and must stay 5 feet off the side lot lines.
Floor area, lot coverage and height
What counts as floor area. Under KZC 115.42, F.A.R. counts the entire area inside the exterior walls on every level, including an attached garage, plus the roof area of any carport. It leaves out attic space under 5 feet of headroom, floor area whose ceiling is less than 6 feet above finished grade, uncovered decks, and porches open on at least three sides. Rooms with ceilings over 16 feet count twice, so a 400 square foot living room with an 18 foot ceiling uses 800 square feet of your allowance.
There is a design bonus: an additional 5 percent F.A.R. above the zone maximum if the house uses at least two of these: center-peaked roofs of at least 4 in 12, side setbacks of 7.5 feet, or upper floors at least 15 percent smaller than the ground floor.
Lot coverage is more than the roof. KZC 115.90 counts all structures and all other hardscape, so the driveway, patio, walks and sport court all come out of the 50 percent. Small pavers (10 by 10 inches or less) and grass grid paving count at half, but that discount cannot exceed 10 percent of the lot.
Height. Kirkland measures height above average building elevation, a weighted average of existing grade at the midpoint of each wall segment (KZC 115.59). It uses pre-development grade, and if fill was placed in the prior ten years, the grade from before the fill. Chimneys and vents may exceed the limit, skylights by 6 inches (KZC 115.60).
Garages, ADUs and accessory structures
- Attached garage. It counts toward F.A.R. like any other room. If its doors face the street, it cannot sit forward of the rest of the ground floor facade, and the doors cannot take up more than 50 percent of the facade width (waived on lots under 55 feet wide). If an alley serves the lot, garages must enter from the alley (KZC 115.43).
- Detached garage or ADU behind the house. The first 500 square feet (lots under 8,500 square feet) or 800 square feet (larger lots) is left out of F.A.R. when the structure sits behind the house. Without an alley, a garage or detached ADU may come within 5 feet of the rear line if the part inside the rear yard is no taller than 15 feet above ABE (KZC 115.42 and 115.115).
- Sheds, detached garages, greenhouses and similar accessory structures. Together they are capped at 1,200 square feet plus 10 percent of the lot area above 7,200 square feet. On a 10,000 square foot lot that is 1,480 square feet (1,200 + 0.10 x 2,800). Their height is the lower of the zone limit or 15 feet above the roof peak of the house. ADUs are not part of this cap (KZC 115.08).
Waterfront lots on Lake Washington
I often work on waterfront lots, and on these lots the shoreline chapter often decides more than the zone table. The code defines shorelands as the land within 200 feet of the ordinary high water mark (OHWM), and for Lake Washington it sets the OHWM at a lake elevation of 18.5 feet (NAVD 88). You establish it by survey (KZC 83.80, 83.90).
- Shoreline setback. Measured from the OHWM, and it depends on your shoreline environment designation. In the Residential-L environment it runs from the average setback of the neighboring houses, never less than 15 feet, in R-L (A), to percentages of the average parcel depth elsewhere: for example 30 percent, at least 30 feet and never required to exceed 60 feet, in R-L (B).
- The submerged part of the lot does not count. Land waterward of the OHWM cannot be used to determine lot size (KZC 15.10.020 and 83.190).
- Its own chart. For shoreline uses, the dimensional standards come from the chart in Chapter 83 (KZC 15.05.020), so check height and coverage there as well as in the zone table. That chart sets 50 percent lot coverage for a detached house in the Residential-L environment, and where its height limit differs from the zone table, the lower of the two applies (KZC 83.190).
- No middle housing. Chapter 113 does not apply inside shoreline jurisdiction.
How I approach design on these lots is on the Kirkland waterfront architect page.
The tree code (KZC 95)
A new house or a demolition needs a tree retention plan from a qualified arborist. A regulated tree is 6 inches in diameter or more, and a landmark tree is 26 inches or more. Landmark trees, groves and any viable tree with its trunk in a required yard rank as high retention value. Additions and remodels below 50 percent of the existing footprint, with no work in a regulated tree’s critical root zone (a radius of 1 foot per inch of trunk diameter), do not need the plan.
No tree may come down until the plan is approved and permits are issued, and not during demolition unless the city approves it in writing. On the other side, the code says the city will not require retention that would reduce the maximum F.A.R. or lot coverage, or prevent ADUs allowed under KZC 115.07. New planting must reach at least 50 tree credits per acre. For how tree rules shape design in general, see my guide to building around trees.
Recent changes: middle housing and ADUs
On June 17, 2025 the City Council adopted Ordinance O-4905, which brought the code in line with state law on middle housing (HB 1110), ADUs (HB 1337), parking and design review. The city states that property owners are not required to add middle housing and can still build a single house.
What the middle housing chapter (KZC 113) now allows in these zones, as an alternative to one house: cottages, multiplexes of up to four units, townhouses and stacked flats. A lot may have the greater of four units, or twice the number of houses the zone allows, and six units within a quarter-mile walk of a major transit stop. F.A.R., lot coverage and height follow the base zone, and the yards are 20 feet front, 5 feet side and 10 feet rear from the project’s outer lines. The chapter does not apply in RSA 1, the Goat Hill overlay or shoreline jurisdiction. More on the state law is in my HB 1110 guide.
Remodeling a house that breaks today’s rules
Plenty of older houses sit inside today’s yards or above today’s height limit. KZC 162.35(7) is the rule to know: any structural alteration of a roof or exterior wall that does not comply with the height or required yard standards means the nonconforming height or setback must be brought into conformance. Repair and maintenance of structural members is excepted. So if a wall already sits 3 feet from a side line, rebuilding that wall or the roof above it can mean pulling it back to the setback. Other nonconformances must be corrected when the work in any 12 month period costs more than 50 percent of the improvement’s replacement cost.
When the plan you want triggers these rules, compare it honestly with a rebuild. As planning ranges, a whole house renovation runs $300 to $550 per square foot, new custom construction $400 to $900 per square foot, and demolition typically $20,000 to $50,000. The wider decision is in remodel or tear down.
How zoning fits into the permit
Zoning is reviewed inside the building permit, alongside the tree plan and, on the water, shoreline review. The steps are in my Kirkland building permit guide. For planning I use Seattle’s permit times as a benchmark, 6 to 10 months for a new house and about 2 to 3 months for a remodel, and 18 to 30 months from design start to occupancy; big trees and waterfront push toward the long end. The full sequence is in the custom home timeline.
I put the survey, the arborist’s tree plan and the F.A.R., coverage and ABE numbers on one site plan first, so the house is drawn inside the real envelope. Piper Cole designs houses and administers construction on your behalf; the firm does not build.
Before you design
Find out what your lot will actually carry
Send me the address and what you have in mind. I will tell you which of these rules is likely to decide your house and what to check first.
Questions
What does RSX mean in Kirkland zoning?
RSX is one of Kirkland’s low density residential zone families, alongside RS and RSA. The number after it is the minimum lot size in thousands of square feet, so RSX 7.2 means 7,200 square feet. Compared with RS, RSX zones require 5 foot side yards with no 15 foot combined total, and allow 30 feet of height above average building elevation instead of 25. Front yard (20 feet), rear yard (10 feet), 50 percent lot coverage and the floor area ratio are the same as the matching RS zone. Source: KZC 15.30, as of September 2026.
What are the setback requirements in Kirkland?
For a detached house in Kirkland’s RS, RSX and RSA zones, the front yard is 20 feet and the rear yard is 10 feet. Side yards are 5 feet each, and in RS zones the two side yards must also add up to at least 15 feet. Corner lots and lots with two street frontages have special rules, and waterfront lots add a shoreline setback measured from the ordinary high water mark. Source: KZC 15.30 and Chapter 83, as of September 2026; confirm with the city.
What is the difference between RS 7.2 and RSX 7.2?
Both have a 7,200 square foot minimum lot, a 50 percent floor area ratio, 50 percent lot coverage, a 20 foot front yard and a 10 foot rear yard. The differences are side yards and height. RS 7.2 needs side yards of at least 5 feet that add up to 15 feet and limits height to 25 feet above average building elevation. RSX 7.2 needs 5 feet on each side and allows 30 feet. Source: KZC 15.30, as of September 2026.
How big a house can I build on a Kirkland lot?
The floor area ratio (F.A.R.) sets the cap: 50 percent of lot size in the RS and RSX 5.0 to 8.5 zones, RS 6.3 and RSA 4 to 8, 35 percent in the 12.5 zones and 20 percent in RS 35, RSX 35 and RSA 1. A 10,000 square foot RS 8.5 lot allows 5,000 square feet of gross floor area. Attached garages count, rooms taller than 16 feet count double, and a design bonus adds 5 percent F.A.R. for certain roof and massing choices. Source: KZC 15.30 and 115.42, as of September 2026.
How tall can a house be in Kirkland?
In RS zones a detached house may be 25 feet above average building elevation. In RSX and RSA zones the limit is 30 feet, with 35 feet for RSA lots in the Juanita Beach Camps and Carr’s Park plats. Average building elevation is a weighted average of existing grade at the midpoint of each wall segment, calculated under KZC 115.59. Chimneys and vents may exceed the limit and skylights may exceed it by 6 inches. Source: KZC 15.30, 115.59 and 115.60, as of September 2026.
Does a garage count toward floor area in Kirkland?
An attached garage counts toward floor area ratio because Kirkland counts everything inside the exterior walls, and carports count by roof area. A detached garage or detached ADU located behind the house is partly exempt: the first 500 square feet on lots under 8,500 square feet, or the first 800 square feet on larger lots. All accessory structures together are also capped at 1,200 square feet plus 10 percent of lot area above 7,200 square feet. Source: KZC 115.42 and 115.08, as of September 2026.
How do I find my zoning in Kirkland?
The City of Kirkland’s Zoning Code FAQ recommends Kirkland Maps: click the Task tab, then the Address button, and enter your address. The Parcel and Permit History link shows the zoning, and the Parcel Zoning link opens the matching section of the online Kirkland Zoning Code. The city also publishes a citywide zoning map as a PDF. Check for overlays such as Holmes Point or Goat Hill, and for the shoreline jurisdiction within 200 feet of Lake Washington.
Can I build more than one home on my Kirkland lot?
A single-family lot in Kirkland generally allows one house plus up to two accessory dwelling units (RSA 4 lots in the Goat Hill overlay are limited to one attached ADU). Since Ordinance O-4905 (June 2025), Chapter 113 also allows middle housing as an alternative to one house: generally the greater of four units per lot or twice the zone’s house count, and six within a quarter-mile walk of a major transit stop, with floor area, coverage and height set by the base zone. Middle housing does not apply in RSA 1, the Goat Hill overlay or shoreline jurisdiction. Confirm with the city.
What is Kirkland Zoning Code Chapter 95?
KZC Chapter 95 is Kirkland’s tree management and landscaping code. A new house or demolition needs a tree retention plan from a qualified arborist. Trees of 6 inches in diameter or more are regulated, trees of 26 inches or more are landmark trees, and trees with trunks in required yards get high retention priority. No tree may be removed until the plan is approved and permits are issued. The city will not require retention that reduces allowed floor area or lot coverage. Source: KZC 95, as of September 2026.
Authoritative sources
Regulatory requirements referenced in this guide are set by the official agencies below. Rules change, always confirm current requirements with the source:
