Addition Plan Check

Additions are where setback and lot coverage violations happen most often. Your existing house was compliant when built — but adding square footage changes the math on lot coverage, FAR, setbacks, and parking. What was legal before may not be legal after an addition.

Critical checks for additions in San Francisco:

• Lot coverage impact — Your addition's footprint adds to the existing building footprint. If the combined coverage exceeds San Francisco's limit (typically 40–50%), the addition will be denied without a variance.
• FAR recalculation — A second-story addition doesn't change lot coverage but significantly impacts FAR. Calculate total floor area (existing + proposed) against your zone's FAR limit before designing.
• Side setback increases for two-story — Many California cities require additional side setbacks for two-story construction. A ground-floor addition may be fine at 5' from the property line, but a second story might need 7–8'.
• Parking displacement — If your addition eliminates existing parking (like building over a driveway pad), you may need to provide replacement spaces elsewhere on the lot.
• Existing nonconformities — If the original house already violates current setbacks or height limits (legal nonconforming), an addition cannot extend the nonconformity. The new portion must fully comply with current codes.

Enter your combined dimensions (existing + proposed) in the form above. We'll check the total project against San Francisco's current codes so you know where you stand before hiring an architect.