ADU Surveys in El Sobrante, CA

El Sobrante has no city hall — ADU applications run through Contra Costa County's Department of Conservation and Development, and the county's ADU checklist sets the terms: site plans on full-size sheets showing property lines with dimensions, lot size, roadways and easements, every building with setbacks, the locations of water and sewer lines for detached units, trees over 20 inches in circumference within 50 feet of the construction area (with species and size), and parking. A grant deed with the legal description rides along with the application. Then comes the trigger that matters most here: the county may require a geotechnical report where the site slopes more than 5 percent — just one foot of fall across the ADU footprint — with an exemption available only below roughly 25 percent slope on ground with no history of settlement, spreading, expansion, or creep. In a valley community whose lots climb from San Pablo Dam Road toward the reservoir watershed, most backyards clear that 5 percent bar without trying.

El Sobrante's semi-rural character adds its own survey questions. Larger parcels — some with horse facilities, long driveways, and decades of casual fencing — carry boundary uncertainty that tighter city grids don't, and an ADU sited off the wrong fence line has more room to go wrong. Septic parcels need dispersal-field clearances mapped alongside the new unit, creek-adjacent lots pick up county setback review, and long driveways to an upper building site must meet county and fire-district grade standards. Our laser-scanned site survey resolves all of it in one mobilization: boundary from record research and monument evidence, slope quantified against the county's geotech thresholds, trees at the 20-inch-circumference cutoff mapped, and water and sewer routing documented for the detached-ADU requirement.

Deliverables are a stamped site plan base map and layered DWG, with records through the Contra Costa County Recorder and County Surveyor in Martinez. For terrain-led questions — driveway profiles, creek sections, hillside pads — see our El Sobrante topographic surveys.