Snohomish County, WA Building Setbacks & Zoning: Lot Coverage Limits (2026)

032 (urban residential zones) that set lot coverage, along with setbacks, height, and lot dimensions, for every zone in unincorporated Snohomish County. Under subsection (1), those two tables 'contain the setback, lot coverage, building height, and lot dimension regulations for all zones,' and subsection (3) requires every lot and structure to conform to them unless modified elsewhere in the title. The actual coverage percentages sit in the tables themselves: the Forest (F), Forest & Recreation (F&R), RRT-10, R-5, RD, RB, RFS, RI, SA-1, RC, RU, R-20,000, R-12,500, and WFB zones are all capped at 35 percent, as are the R-9,600, R-8,400, and R-7,200 urban residential zones.

Commercial and industrial zones vary widely: NB allows 65 percent, CB, GC, IP, and BP allow 35 to 50 percent, and CRC allows 30 to 50 percent depending on table notes, while PCB, LI, HI, and UC carry no maximum at all. The LDMR urban residential zone gets a higher 50 percent cap under a table note, and A-10 agricultural land has no lot-coverage limit either. 040(8) clarifies what counts toward the cap: 'Lot coverage includes all buildings on the given lot,' covering every structure, not just the main house.

010(5) gives the planning director limited flexibility to reduce a required setback, not the coverage percentage itself, by up to 25 percent for short walls or structures 20 feet or less in length, provided a three-foot minimum setback remains, and subsection (9) clarifies that for setback purposes the RI zone counts as industrial and the RB, CRC, and RFS zones count as commercial.