Sammamish limits how much of a residential lot can be covered by buildings and hard surfaces. Maximum building lot coverage is about 40% in R-4 and 50% in R-6, and maximum impervious surface ranges from 30% in R-1 up to 85% in R-12 and R-18, with special rules for large lots.
Sammamish caps both lot coverage (the building footprint share of the lot) and impervious surface (all hard surfaces). According to the City's Lot Coverage and Impervious Surface handout (No. 150), maximum lot coverage is 40% in the R-4 zone and 50% in the R-6 zone, and maximum impervious surface is 30% in R-1, 75% in R-8, and 85% in both R-12 and R-18. Minimum landscaped yard area is 45% in R-4 and 35% in R-6. Lot coverage is calculated by dividing the total building footprint by the lot size; for example, a 10,000-square-foot lot with 3,700 square feet of buildings has 37% coverage. Roof eaves longer than 18 inches count toward lot coverage. For impervious surface, if a lot is under half an acre it follows the nearest R-4, R-6, or R-8 rules, and if a lot is over half an acre the impervious surface is limited to 10,000 square feet or 30% of the property, whichever is less. Lot coverage may be increased by 5% one time if a covered (not fully enclosed) outdoor living space or an accessory dwelling unit is added. The City's R-4 development standards list a 40% maximum hardscape coverage and a 3,000-square-foot maximum building footprint. The handout cites the prior code numbering (SMC 21A.25.070); these standards now appear under the City's Title 21 development code. These are city rules, not King County standards.
Covering more of the lot with buildings or hard surfaces than the zone allows is a zoning violation that can block permit approval. After-the-fact over-coverage can require removal of structures or paving, conversion to pervious surfacing, or other corrective action to bring the lot back into compliance.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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Sammamish does not prohibit backyard composting, and curbside yard waste/compost collection is available citywide. Curbside garbage, recycling, and yard-wast...
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Artificial turf is allowed in Sammamish and counts as 'yard area' for landscaping purposes. However, the city's surface water rules (based on the King County...
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Sammamish encourages native and drought-tolerant landscaping and requires it in certain contexts. The landscaping code (SDC 21.07.070) calls for drought-tole...
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Rainwater harvesting is legal in Sammamish and across Washington. Under a 2009 Washington Department of Ecology policy, collecting rooftop rainwater for on-s...
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The City of Sammamish runs no water utility and imposes no mandatory citywide watering restrictions. Water comes from special-purpose districts — chiefly Sam...
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Sammamish does not set a numeric weed-height limit, but its landscaping standards (SDC 21.07.070) prohibit any plant on the King County noxious weed list acr...
Side-by-side rule comparisons with other cities in King County.
See how other cities in King County handle lot coverage limits.
See how Sammamish's lot coverage limits rules stack up against other locations.
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