Issaquah, WA Accessory Structures: Shed & Carport Rules (2026)

LUC 18.508.030 applies to utility sheds and buildings, greenhouses, mechanical equipment, and minor elements such as decks, porches, patios, walkways and ramps. Under subsection (B), accessory structures cannot be located in or on a public utility or access easement, must comply with required setbacks unless specifically excepted, and cannot be located in a front setback area.

For sheds, greenhouses and other accessory buildings, subsection (C) sets the numbers. An accessory building exceeding 200 square feet in floor area requires a building permit. The height of a detached accessory building in a residential zone cannot exceed one story and cannot exceed 15 feet. The building must be located a minimum of six feet from the principal structure. On a corner lot it must be set back from the street at least as far as any primary structure of an adjacent lot, as shown in Figure 18.508.030(C). This section does not restate side and rear setback distances; it points to the required setbacks of the zone.

To count as an accessory use at all, LUC 18.508.020 requires that the use be on the same lot as a principal or primary use, have similar or consistent impacts as the principal use, and be subordinate or dependent on it. Accessory dwelling units are regulated separately under IMC 18.500.090 and are not subject to the chapter.

Equipment next to a shed falls under subsection (D). Heat pumps, air conditioner condensers and similar mechanical equipment on single-family and townhome lots must not exceed 55 dbA during the day and 45 dbA at night as measured at the property line. If that State-adopted standard cannot be met, the units must provide mitigation: placement farthest from neighboring properties as practically feasible, a fencing or vegetation buffer, and quieter components such as a sound blanket or quieter fans. Mechanical equipment in a side setback must be placed adjacent to the primary structure as operationally feasible.

Decks, porches, patios, walkways and ramps follow subsection (E). A structure with a floor height 30 inches or more above finished grade must obtain a building permit. A structure under 30 inches can extend into a side or rear setback, but no closer than three feet from any property line. Ramps required for barrier-free access can extend into required setbacks only to the extent necessary to meet the Building Code.