Portland residential zones cap lot coverage at 50% in R5/R7 and 60% in R2.5 (PCC 33.110). Unincorporated Multnomah County RR zones typically cap at 25% building coverage. Lot coverage calculations include the footprint of all structures with a roof. Stormwater management requirements apply to impervious surfaces over 500 sq ft or 50% of the lot.
Portland City Code 33.110.225 sets maximum building coverage in single-dwelling zones: R20/R10 (30%), R7 (40%), R5 (50%), R2.5 (60%). Building coverage is calculated as the total roofed footprint of all structures on the lot. Portland's Clean River Rewards program and Stormwater Management Manual (Title 17) require on-site stormwater management for new or redeveloped impervious surface over 500 sq ft in most cases, using rain gardens, drywells, eco-roofs, or permeable paving. Impervious surface coverage is distinct from building coverage - driveways, patios, and walkways count against impervious limits but not building coverage unless roofed. Gresham Development Code sets residential coverage at 40-50%. Troutdale permits up to 40% in R1 and 55% in R3. Unincorporated Multnomah County MCC 39 Rural Residential zones cap at 25% building coverage with much larger minimum lot sizes. MUA-20 allows 15-25% coverage depending on parcel use. EFU parcels have dwelling footprint limits rather than coverage percentages. Permeable pavers and eco-roofs may receive partial credit under stormwater rules. Coverage violations require adjustment (variance) and can delay permits significantly.
Exceeding building coverage: stop-work order and required correction. Portland BDS penalty $500 to $5,000. Unpermitted impervious surface causing stormwater issues: $500 to $25,000 under PCC 17.38 stormwater penalties. Required adjustment ~$2,500 fee.
Multnomah County, OR
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Multnomah County, OR
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Multnomah County, OR
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Multnomah County, OR
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Multnomah County, OR
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See how Multnomah County's lot coverage limits rules stack up against other locations.
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