King County, WA Landscaping Rules: Artificial Turf (2026)

King County Code does not prohibit artificial turf on private residential parcels. In the Puget Sound region, synthetic turf is less common than in California because natural turf thrives in the marine climate, but artificial turf is permitted for landscaping, sport courts, and play areas. The primary regulatory concern is stormwater. Under the 2019 King County Surface Water Design Manual (SWDM) and the NPDES Municipal Stormwater Permit issued under RCW 90.48 and the federal Clean Water Act, synthetic turf is typically treated as impervious or partially impervious surface depending on drainage design. If total new impervious surface including turf exceeds 2,000 square feet on a lot, stormwater mitigation such as dispersion, rain gardens, or detention may be required. Critical areas including wetlands, stream buffers, and shoreline setbacks generally prohibit synthetic turf because crumb-rubber infill and microplastics can leach into salmon streams. Public installations at schools and parks are addressed separately by KCC and WAC. Some HOAs restrict or prohibit artificial turf, particularly in front yards. Drainage plans should be reviewed when the turf exceeds modest residential sizes.