ADU Hillside Foundation & Slope Stability Investigation in Hillsborough, CA

Hillsborough issued 56 ADU permits out of 58 total homes approved in 2025 -- one of the highest ADU shares in California. Most of those lots sit on graded hillside terrain, which means slope stability, not just soil bearing capacity, drives the design.

AK Geotech provides geotechnical investigations built specifically for Hillsborough's terrain and permitting process. Because so many Hillsborough parcels involve cut/fill slopes, retaining structures, or proximity to existing grading, the town's plan checkers routinely require a slope stability analysis alongside the standard soils report -- and an incomplete submittal is one of the most common causes of permit delay on hillside ADU projects.

Our scope for a typical Hillsborough ADU investigation includes subsurface exploration, bearing capacity and settlement analysis, slope stability calculations for any adjacent cut or fill slopes, and seismic design parameters per current California Building Code requirements. Where an existing retaining wall or graded slope is near the proposed ADU footprint, we evaluate its condition and factor it into the foundation recommendation.

What's included

• Subsurface exploration and soil classification

• Slope stability analysis for adjacent graded slopes

• Foundation type and bearing capacity recommendations

• Seismic design parameters (current CBC)

• Formal geotechnical report for permit submittal

If you're planning an ADU on a hillside lot in Hillsborough, reach out to AK Geotech for a scope and proposal tailored to your site.