Issaquah zoning and building permits: what you can build on your lot in 2026

Short answer: on a typical Issaquah single-family lot you can build one house of up to 30 feet (measured from average grade to the midpoint of a pitched roof), plus up to two ADUs, inside your zone’s yards and a limit on how much of the lot is roof and paving. On the hillsides around town, the geotechnical report, the slope rules and the tree code often decide more than the zone does.

How I work here is on my Issaquah architect page. A word on sources: the “18.404 Form and Intensity” PDF that ranks for Issaquah zoning is an April 2022 draft, and the SF-S amendments PDF dates from 2019 and cites the old code. The adopted code came from Ordinances 3011 to 3022, in effect since June 1, 2023, and amended since. Everything below comes from adopted ordinances and city handouts as of September 2026; the city keeps amending Title 18, so confirm before you rely on any number.

Issaquah’s single-family zones and the zoning map

The Land Use Code is Title 18 of the Issaquah Municipal Code; Chapter 18.404, Form and Intensity, holds the numbers. The residential zones are C-Res (Conservancy Residential), SF-E (Estates), SF-S (Suburban), SF-SL (Small Lot), SF-D (Duplex), and the Urban Village zones UV-SF and UV-MF used in the Issaquah Highlands and Talus.

• SF-E is meant for larger lots and hobby farms “while protecting critical areas,” such as wetlands, steep slopes and flood hazard areas.
• SF-S provides single-family neighborhoods “in an urban setting.” This is the zone people search as “SFS zoning.”
• SF-SL suits medium density areas near urban services, SF-D adds duplexes, and C-Res protects wetlands, hillsides and flood areas.

Finding your zone. The city posts its official zoning map as a PDF on the Static Maps page of issaquahwa.gov, alongside interactive maps. If your parcel shows a zone such as RA-5, it is outside the city’s zone list: RA-5 is a King County rural area zone (0.2 homes per acre base density), and county rules apply.

Issaquah Highlands and Talus. These are Urban Village zones with their own tables (IMC 18.404.160 and 18.404.170), and the code says the Architectural Review Committee may apply more restrictive setbacks than the city. The city’s submittal checklist requires the Highlands ARC stamp on the site plan and elevations before you submit.

Setbacks, impervious surface and height by zone

These are the standards for a detached house in Table 18.404.090(A), which was restated in April 2025 (Ordinance 3088) with the single-family figures unchanged.

Zone	Minimum lot	Front	Side	Rear	Max impervious	Base height
SF-E, Single-Family Estates (1.24 homes per acre)	35,000 sq ft, 135 ft wide	30 ft	15 ft	30 ft	30%	30 ft
SF-S, Single-Family Suburban (4.5 per acre)	9,600 sq ft, 70 ft wide	20 ft	8 ft	10 ft	40%	30 ft
SF-SL, Single-Family Small Lot (7.26 per acre)	6,000 sq ft	10 ft	6 ft	20 ft	50%	30 ft
SF-D, Single-Family Duplex (house)	6,000 sq ft, 50 ft wide	10 ft	6 ft	10 ft	50%	25 ft or 2 stories, whichever is lower
C-Res, Conservancy Residential (1 home per 5 acres)	5 acres	75 ft	75 ft	75 ft	10%	30 ft

Source: IMC Table 18.404.090(A), Residential Zones Form and Intensity Standards, as adopted by Ordinance 3015 and restated by Ordinance 3088. SF-SL has no minimum lot width. Maximum building height is listed as N/A in the SF zones, so the base height is the limit.

How the yards work (IMC 18.404.030):

• Corner lots have a front setback from each street. On an SF-S corner lot that is 20 feet on two sides.
• Projections. Eaves, chimneys, gutters and bay windows may reach up to 18 inches into a setback, but must stay at least 3 feet from the property line. Bay windows may not exceed 30 percent of the facade or add floor area.
• Critical areas have their own setbacks (Chapter 18.802), and where two standards apply, the more restrictive one wins.

How big a house the rules allow

Issaquah uses floor area ratio only in Central Issaquah, Talus and the Highlands (IMC 18.404.070). In SF-E, SF-S and SF-SL there is no floor area cap. The envelope is the yards, the height and the impervious limit.

Impervious surface (IMC 18.404.040) adds up the building footprint, gravel and paved parking and driveways, walkways, decks, patios, porches, sport courts and pools. Eaves of 18 inches or less are left out; overhangs and cantilevered decks beyond 18 inches count in full. Grass is not impervious. Pervious pavers used for parking or walks do not count toward the pervious area you must keep, and the pervious area must be landscaped.

Before any critical areas: a 9,600 square foot SF-S lot allows 3,840 square feet of impervious surface (9,600 x 0.40). A 35,000 square foot SF-E lot allows 10,500 (35,000 x 0.30). A 6,000 square foot SF-SL lot allows 3,000 (6,000 x 0.50). On a 70 foot wide SF-S lot, 8 foot side yards leave a 54 foot wide building zone (70 minus 16).

Height (IMC 18.404.050, clarified by Ordinance 3067 in 2024): 30 feet in SF-E, SF-S and SF-SL, measured from average grade to the midpoint of the highest gable on a roof pitched between 4:12 and 12:12, or to the top of the coping on a flat roof. Average grade is found by taking spot elevations every 10 feet around the footprint, using existing or finished grade, whichever is lower, and averaging them. No part of a shed roof may rise above the base height, and chimneys and solar panels are exempt. On the shoreline, height is measured from the average existing grade under the building.

Sheds and other detached accessory buildings are held to one story and 15 feet and cannot sit in the front setback; a detached ADU follows the house height instead (Ordinance 3092). With alley access, the garage must come off the alley where feasible, and a street-facing garage may not exceed 50 percent of the house width unless the facade is under 36 feet.

Steep slopes, landslide and coal mine hazards

The city says its critical areas mapping identifies unstable soils in limited hillside areas. There, these rules come first:

• Steep slope hazard areas (40 percent or steeper). A minimum buffer of 50 feet, measured horizontally from the top or toe, with native vegetation kept. A critical areas study can reduce it to as little as 10 feet, but an occupied building must stay at least 25 feet from the top or toe, and you record a notice to future buyers and sign a hold harmless agreement (IMC 18.802.130.D). The house cannot sit on the 40 percent slope itself: the code allows only drainage, trails and utilities there, unless a slope with 20 feet or less of vertical change is exempted (IMC 18.802.180).
• Landslide hazard areas. A minimum 50 foot buffer on all sides, which the study can widen at the crown or toe, or trim to 15 feet on the flanks. The buffer can be removed only if the risk is permanently mitigated to a factor of safety of 1.5 static and 1.1 seismic.
• Building setback from the buffer. A further 15 foot building setback applies from the outer edge of the buffer for steep slope and landslide hazard areas, wetlands and habitat areas, and since July 2024 streams too (IMC 18.802.450).
• Coal mine hazard areas. The city keeps coal mine hazard maps. Severe mine hazard zones carry a 15 foot buffer with no occupied buildings.

The forested hillside chapter (IMC 18.810) covers the in-between slopes: any work that disturbs ground on slopes of 15 percent or more with at least 10 feet of vertical rise. Mass regrading to make a flat pad is prohibited, cuts and fills are limited to 10 feet, retaining walls to 10 feet, and walls that only raise the grade in a required setback to 6 feet (walls over 4 feet need a building permit). Houses generally may not break a natural ridgeline, and the chapter measures height on slopes from existing grade without averaging, so ask the city early which method governs your lot. My remodel or tear down guide covers how these costs change the decision.

The tree code

Chapter 18.812 was rewritten in part by Ordinance 3114, effective October 14, 2025. A significant tree is 6 inches in diameter or more (8 inches for alder and cottonwood), and a landmark tree is over 30 inches. The key rules for a new house or a redevelopment that expands the footprint or paving:

• Retention. In residential zones you keep 35 percent of the total diameter of all significant trees in the developable site area. First priority goes to healthy trees, trees on slopes over 20 percent, conifers such as Douglas fir and western red cedar, and trees over 60 feet tall or 18 inches in diameter.
• Canopy target by lot size. Single-family lots over 15,000 square feet target 60 percent canopy, 10,000 to 14,999 square feet 45 percent, 5,000 to 9,999 square feet 35 percent, and smaller lots 25 percent. New trees count at their projected size at 20 years.
• Room to build. The construction limit line must stay at least 5 feet outside the drip line (the outer edge of the canopy) of a protected tree.

On a wooded hillside the tree plan and the slope plan are one drawing; see my guide to building around big trees.

Lake Sammamish lots

Shoreline jurisdiction reaches 200 feet landward of the ordinary high water mark (the normal waterline), which the city sets at elevation 31.76 feet (NAVD88) for Lake Sammamish unless a biologist fixes it in the field. The Shoreline Master Program sets a 35 foot vegetated buffer plus a 15 foot building setback, and a new house and all its paving must sit behind both unless you win a shoreline variance. New development must also plant 80 percent of the buffer with native woody species; 20 percent may stay as lawn or water access. An existing house can expand without a variance if the addition stays out of the buffer and the 15 foot setback, with buffer planting required once new impervious area passes 500 square feet in five years. The city treats a shoreline exemption as its own application, with a 3 week target for the first review; see my shoreline exemption guide.

ADUs and middle housing

ADUs. Since May 2025 (Ordinance 3092), a single-family lot may have two ADUs, attached, detached or internal. Each is capped at 1,000 square feet unless it is carved from existing space without exterior expansion, and the main house must be at least 25 percent larger than the largest ADU. The city’s FAQ says ADUs follow the zone’s standards, the rear setback does not apply where the lot abuts an alley, and there is no owner occupancy requirement. Since July 28, 2026 (Ordinance 3145), a Washington licensed architect may self-certify a detached ADU for building code compliance, except in a geologically hazardous area; the site plan is still reviewed for zoning, stormwater and critical areas.

Middle housing. Ordinance 3091 (effective May 27, 2025) allows two units per lot in single-family zones, or four if the lot is within a quarter mile walk of a major transit stop or one unit is affordable. It does not apply to the critical area parts of a lot, and HOA documents created on or before July 23, 2023 may still prohibit it. The city’s FAQ confirms you may still replace a house with one detached house. State law background is in my Washington ADU laws guide.

Remodel, rebuild or tear down

Many older Issaquah houses sit inside today’s setbacks. Chapter 18.214 lets a legal nonconforming house be maintained, and modified or expanded as long as the nonconforming part is not increased and the chapter’s approval criteria are met. If the house is demolished, the new one must meet the current code. If it is damaged by accident or nature, a single-family house may be rebuilt regardless of value, provided complete permit applications are filed within one year and the nonconformity is not increased.

For the money side, as planning ranges: whole house renovation $300 to $550 per square foot, additions $350 to $650, new custom construction $400 to $900, and demolition typically $20,000 to $50,000. A 2,500 square foot custom home runs $1.2M to $2.5M all-in. My cost to build a house guide explains the spread.

The building permit: portal, documents and timelines

Community Planning and Development runs permits, and applications go through MyBuildingPermit.com. The city’s checklist for a new single-family house (last updated August 2023) asks for these before and at submittal:

• Before you apply: a water and sewer availability letter (from the Sammamish Plateau Water and Sewer District in its area), a traffic concurrency certificate and King County septic approval where they apply, and possibly a pre-submittal meeting.
• With the application: a geotechnical report and review letter, a stormwater report, stamped structural calculations, the energy code worksheet, a SEPA checklist unless exempt, a critical area study where needed, and drawings with a site plan showing every setback.
• Fees are invoiced once the submittal is deemed sufficient; card payments online are accepted up to $5,000.

Published timelines. The city’s Target Review Timelines handout (updated April 2026) sets 4 weeks for the first review of a single-family permit, 3 weeks for the second and 1 week for each round after. The clock starts when you pay the fees. Each figure is one review round, so total time runs longer. For planning I use 2 to 4 months of design to reach permit submission, Seattle’s permit times as a benchmark, 6 to 10 months for a new house (about 2 to 3 months for a remodel), 12 to 18 months of construction and 18 to 30 months from design start to occupancy; steep lots and big trees push toward the long end. The full sequence is in my custom home timeline.

I start every Issaquah lot with the survey, critical areas map, geotech and arborist, then put the yards, the impervious budget and the height plane on one site plan. Washington law does not require an architect for a house (RCW 18.08.410), but on a hillside lot the sequence matters. Piper Cole designs houses and administers construction on your behalf; the firm does not build.

Questions

What does SF-S zoning mean in Issaquah?

SF-S is Issaquah’s Single-Family Suburban zone, intended for single-family neighborhoods in an urban setting at up to 4.5 homes per acre. The minimum lot is 9,600 square feet and 70 feet wide. A house needs a 20 foot front setback, 8 foot side setbacks and a 10 foot rear setback, may cover no more than 40 percent of the lot with impervious surface, and has a 30 foot base height. Source: IMC Table 18.404.090(A), as of September 2026; confirm with the city.

What is the difference between SF-S and SF-SL zoning in Issaquah?

SF-SL, Single-Family Small Lot, allows smaller lots and more coverage than SF-S. SF-SL needs a 6,000 square foot lot with no minimum width, a 10 foot front, 6 foot side and 20 foot rear setback, and allows 50 percent impervious surface. SF-S needs 9,600 square feet and 70 feet of width, with 20 foot front, 8 foot side and 10 foot rear setbacks and 40 percent impervious surface. Both have a 30 foot base height. Source: IMC Table 18.404.090(A), as of September 2026.

Where can I find the Issaquah zoning map?

The City of Issaquah posts its official zoning map as a PDF on the Static Maps page of issaquahwa.gov and also offers interactive maps. Check whether your lot is in an Urban Village zone such as the Issaquah Highlands or Talus, which have their own standards and architectural review, and whether any critical areas or the Lake Sammamish shoreline apply. A parcel zoned RA-5 is under King County rural zoning, not city zoning.

How tall can a house be in Issaquah?

In the SF-E, SF-S and SF-SL zones the base building height is 30 feet, and in SF-D it is 25 feet or two stories, whichever is lower. Height is measured from average grade, using spot elevations every 10 feet around the footprint at existing or finished grade, whichever is lower, to the midpoint of the highest gable of a 4:12 to 12:12 roof or the top of a flat roof. On hillside sites the forested hillside chapter measures height from existing grade without averaging. Source: IMC 18.404.050 and 18.810.030, as of September 2026.

How much of my Issaquah lot can I cover?

Issaquah limits impervious surface rather than floor area in its single-family zones: 30 percent in SF-E, 40 percent in SF-S and 50 percent in SF-SL and SF-D. Impervious surface includes the building footprint, driveways and parking, walkways, decks, patios, porches, pools and sport courts. Eaves of 18 inches or less are excluded and grass is not impervious. On a 9,600 square foot SF-S lot that is 3,840 square feet. Source: IMC 18.404.040 and Table 18.404.090(A), as of September 2026.

Can I build on a steep slope in Issaquah?

Near a steep slope, yes, with limits; on it, generally no. A house cannot sit on a steep slope hazard area (40 percent or steeper) itself, where the code allows only drainage, trails and utilities unless a slope with 20 feet or less of vertical change is exempted. Those slopes carry a 50 foot buffer from the top and toe, which a critical areas study can reduce to 10 feet, but an occupied building must stay at least 25 feet from the top or toe, plus a 15 foot building setback from the buffer edge. Landslide hazard areas carry a 50 foot buffer. Ground disturbance on slopes of 15 percent or more with 10 feet of rise also falls under the forested hillside rules, which limit cuts, fills and retaining walls to 10 feet. Source: IMC 18.802.130, 18.802.180, 18.802.450 and 18.810, as of September 2026.

How long does a building permit take in Issaquah?

The City of Issaquah’s Target Review Timelines handout, updated April 2026, targets 4 weeks for the first review of a single-family residential building permit, 3 weeks for the second review and 1 week for later rounds. The clock starts when permit fees are paid, and each target covers one review round, so total time runs longer. As a benchmark, Seattle permits take 6 to 10 months for a new house and about 2 to 3 months for a remodel. Applications are filed through MyBuildingPermit.com.

How many ADUs can I build on an Issaquah lot?

Since May 2025, a lot with a single-family home may have two ADUs in any mix of attached, detached or internal. Ordinance 3092 limits each ADU to 1,000 square feet unless it is created from existing space without exterior expansion, and the main house must be at least 25 percent larger than the largest ADU. The city’s FAQ says ADUs must meet zoning standards except the rear setback where the lot abuts an alley, and owners do not have to live on site. Since July 28, 2026 a Washington licensed architect may self-certify a detached ADU except in geologically hazardous areas. Confirm with the city.

Authoritative sources

Regulatory requirements referenced in this guide are set by the official agencies below. Rules change, always confirm current requirements with the source:

• Seattle Dept. of Construction & Inspections (SDCI)