Hillside lots and
historic zones.

Hillside: what actually triggers it

The Baseline Hillside Ordinance (BHO) applies to lots with a natural slope of 15% or greater, based on USGS topographic data — not a judgment call, a measurable threshold. If your lot crosses it, a specific set of grading, height, and floor-area rules kicks in that a flat-lot project never has to think about.

Hillside: the actual numbers

• Grading limit: 500 cubic yards plus 5% of your lot size, cumulative — meaning total cut and fill combined, not each measured separately.
• Slope steepness: new graded slopes can't exceed a 2:1 ratio (horizontal to vertical) except in specific LADBS-approved cases.
• Height limit: capped at 45 feet, measured from average natural grade — a different, generally stricter method than how height gets measured on a flat lot.
• Floor area ratio: reduced incrementally for lots with 15–30% average slope, and can drop 50% or more below an equivalent flat-lot FAR once slope exceeds 30%.
• Lot coverage: any structure rising more than 6 feet above hillside grade is capped at 20% lot coverage.
• Soils report: a licensed geotechnical engineer has to investigate the site and produce a report meeting LADBS standards, submitted with both the grading and building permit applications.

Historic: what actually triggers it

A Historic Preservation Overlay Zone (HPOZ) requires a Certificate of Appropriateness for exterior work, reviewed against that specific HPOZ's own preservation plan and design guidelines — which vary district to district, since each one reflects the community input and priorities of that specific neighborhood. It applies broadly: additions to an existing single-family home, new single-family construction, some multifamily projects, and commercial or institutional work within the zone.

Historic: what's changing

As of late 2025, LA's Office of Historic Resources has been developing Objective Design Standards specifically for new infill construction, mixed-use infill, and ADUs within HPOZs — aimed at making that review more predictable. The comment period on the initial draft ran through July 2026, with a public approval process expected to begin in fall 2026. If you're planning a project in an HPOZ, it's worth checking where that process currently stands before finalizing a design around the old review criteria.

What this means for your project

Hillside and historic review both add real time and real design constraints — but they're knowable in advance, not a surprise that shows up at plan check. We confirm which overlay (or both) applies to your specific lot before design work starts, so the grading budget, the soils report, or the Certificate of Appropriateness process is built into the plan from day one.