SANTA ANA DUPLEX ADU
Breaking Ground on a Duplex ADU in Santa Ana: Why Line-and-Grade Surveys Matter
We recently broke ground on a duplex ADU project in Santa Ana, and right away the property stood out as a good candidate for development. The lot had ample space to accommodate the ADU, and the setbacks were not overly restrictive. On one side of the property, we were working within a typical 4–5 foot side yard setback. Because of that proximity to the property line, the exterior wall on that side required a one-hour fire-rated assembly, which comes with specific wall and detailing requirements to prevent fire spread between properties. On the opposite side, however, we had a generous 17-foot setback. That extra space gave us flexibility in layout, construction sequencing, and overall site logistics—something that can make a significant difference on tight Southern California lots.
The Importance of a Line-and-Grade Survey
Before any serious foundation work begins, one step should never be skipped: a line-and-grade survey. This means hiring a licensed surveyor to locate and stake the exact property lines and confirm that the proposed building footprint is fully within them. This step is critical, especially in Los Angeles and Orange County, where lots are small, regulations are strict, and ADUs are often designed to maximize every allowable square foot.
A Costly Lesson From the Field
To illustrate why this matters, the surveyor on our project shared a cautionary story. He was called out to a job that had already spent two years in planning and approvals. When he arrived to perform the line-and-grade survey, the contractor had already installed footing trenches, rebar (wrapped in plastic), and underground plumbing. After staking the property lines, the surveyor realized the building footprint was positioned approximately 18 inches into the setback. That meant the structure would need to be shifted a foot and a half.
The problem? There was no room to move it.
The ADU was already tight to the existing house, leaving no space to shift the building footprint. The only option would have been to remove 18 inches of livable space from the ADU itself. That would trigger a full redesign and resubmittal through plan check—adjusting room sizes, hallway widths, kitchen clearances, and other code-required dimensions.
In practical terms, the contractor would have had to:
Remove underground plumbing
Demo rebar
Re-dig footings
Reset form boards
Redesign the building
Re-enter plan check
In other words, start over—at significant cost.
How We Approached Our Santa Ana Project
Fortunately, our Santa Ana ADU project went smoothly. We brought in the line-and-grade survey while the form boards were up but before anything was locked in. Once we received confirmation that the layout was fully within property lines and setbacks, we finalized the form boards, completed footing excavation, and then brought in the plumber to begin underground piping. That sequence matters. Survey first. Lock layout second. Build third.
The Bigger Takeaway
In Southern California, where regulations are high, lots are tight, and homeowners want to maximize buildable area, it is essential to start slow and methodical—especially at the foundation stage. Proper planning, accurate layout, and early verification prevent expensive corrections later when work is already complete. Hiring a contractor who understands these steps ahead of time can save months of delays and tens of thousands of dollars.
In the next blog, I’ll walk through the foundation requirements for this duplex ADU project in more detail. If you have questions or are considering building a new construction ADU in Cerritos, Lakewood, Buena Park, or surrounding areas, feel free to reach out. We’re happy to walk you through what it would take to get your project done correctly from the ground up.