Deep Foundations: The Rigors of Building Hillside Pools

When you build swimming pools and surrounding structures on the hillsides of Los Angeles, you enter a world of extremes—steep terrain, shifting soils, strict regulations, and invisible engineering that must endure for generations, all in a place famous for earthquakes.

By JC Escudero

I often tell clients that the most important parts of a hillside pool project will never be seen again once the job is complete. If we’ve done our work correctly, no one will ever think about the caissons or grade beams that support their stylish slice of panoramic paradise.

But getting to that lofty point is one of the most demanding and highly scrutinized construction processes in the watershaping industry. The projects are intensely challenging for a range of possible reasons including safety, site access and soils conditions. More than anything, the work is nuanced and requires detailed planning, because every site, every design and every client are all different.

It’s serious business that can keep you up at night. Clients have elevated expectations, and sometimes it feels like a high-wire act that mostly takes place underground.

Hillside Ordinance

In the City of Los Angeles, virtually every hillside property—from Calabasas to Los Feliz and along the Santa Monica Mountains Corridor—is subject to the city’s stringent Hillside Ordinance and the jurisdiction of the city’s Grading Division of the Inspection Bureau. These rules are rigorous and were tightened even further after the 2022 adoption of the new California Building Code, and again in 2024, making hillside construction highly regulated.

The painstaking process is, I believe, necessary because the risks associated with structural failures are so extreme, and especially in a region so seismically active it literally experiences hundreds of mostly imperceptibly small earthquakes each day, and some much larger events that make history.

Suffice it to say, failure is truly not an option, and the regulatory environment is designed to help prevent catastrophe, demanding though it may be.    

Every project starts with a Grading Pre-Inspection (GPI)—a mandatory step before design or engineering can even begin. The GPI inspector evaluates the site, reviews topography, slope analysis and surrounding development, and compares the property to nearby projects using a comprehensive internal database. It’s not unusual for the results to specify additional requirements such as soils reports, topographic surveys, and recommendations for structural depth to stable ground.

I tell my clients from the beginning: before we draw anything or spend thousands of dollars on plans, we need that GPI. Ninety-five percent of the time, the GPI will come back requiring a soils report and possibly further requirements.

A vast subject unto itself, the soils report then becomes the foundation for everything else: where the pool goes, what kind of structure it needs, and how deep we’ll have to go to reach competent soil or bedrock.

And, it bears mentioning, all of those factors will often dramatically impact the project’s price tag and timeline. More on client communication below.

Free-Standing

One of the key engineering requirements for hillside pools is that the structure must be capable of freestanding—as if all the soil around it were removed. That’s the concept behind the 40 feet to daylight requirement. The bottom of the foundation must extend deep enough that the structure could theoretically remain stable even if the hill eroded away.

This can have huge design implications. In many cases, the soils engineer will say the bedrock is only eight feet down, but that doesn’t matter if the building department still requires 40 feet of structural depth from the slope. We may end up drilling caissons 20, 30, even 50 feet deep to meet the engineering requirement, and ultimately ensure the pool can safely “float” above the slope on its own secure foundation system.

Once the soils data are in hand, the structural engineer designs the foundation system—typically caissons tied together with grade beams. In theory, the engineer might specify eight piles spaced every twelve feet. On paper that looks fine, but in the real world, that might not be physically possible because of site conditions. Sometimes I have to work with the engineer to develop a more practical plan—fewer caissons, larger diameters, and connecting grade beams that tie everything together structurally.

That was the case on a recent project in Los Feliz, pictured here. The engineer initially called for a series of tightly spaced small-diameter piles. I pointed out that on a steep yard with only limited access, it would be impossible to maneuver the equipment. My solution was to use four larger 36-inch diameter caissons, each drilled about 22 feet deep, connected by a reinforced grade beam.

It achieved the same engineering requirements but in a way that was safer, faster, and more feasible in the field. Otherwise, the project almost certainly would not have ever been built, or at least doubled in price.

The Access Challenge

Of course, nothing about hillside construction is simple—least of all access. The steep terrain, narrow driveways, overhead wires, trees, and neighboring structures all combine to make logistics a daily battle. Sometimes we can get a drilling machine in; sometimes we can’t. When there’s no room for heavy equipment, we end up doing the work by hand, eye and glow sticks.

That means hoisting a worker down into a narrow shaft—helmeted, harnessed, wearing ear protection and respirator—armed with a jackhammer and a bucket. At best, a skilled worker might excavate seven feet per day by hand. Each bucket of dirt and rock must be hauled out, one load at a time. Depending on the conditions, digging a set of caissons can take weeks of slow and grueling labor.

When we can bring in an auger rig, the work moves faster, but access must still be carefully planned. The typical drilling machine is 13 feet long bumper to bumper, 10-feet wide so if your driveway is only eight feet wide, forget it. You might need to crane the machine in—and in Los Angeles, that’s a permit, a traffic control plan, and a multi-thousand-dollar day rate before you even touch the ground.

Safety Supervision

The safety component of this work cannot be overstated. Any time you have workers in confined spaces, deep excavations, or steep slopes, OSHA supervision and compliance become paramount. The Los Angeles grading department also mandates that a Deputy Soils Engineer be present during drilling or excavation. This engineer acts as an on-site safety officer, monitoring air quality, checking for methane or other gases, and ensuring shoring and working conditions meet safety standards.

This is not optional. It’s law—and potentially it’s life or death. There are no cutting corners when you’re 25 feet underground. I’ve heard horror stories from jobs where people didn’t follow procedure, and the results were catastrophic.

Fortunately, and I’m very proud to say, our teams have maintained an impeccable safety record because we approach every project as if OSHA were standing over our shoulders—which, in many cases, they are.

Getting It Right

One of the most critical aspects of hillside work is verifying caisson locations. It sounds obvious, but on a 40-degree slope, a few feet off in any direction can be disastrous. I’ve seen projects where the caissons were badly misplaced, and the entire pool design had to be redrawn. You simply can’t afford those mistakes.

The rebar cages themselves must be built precisely to the plan—typically 30 inches wide for a 36-inch bore to ensure proper concrete coverage of the rebar. Every bend, splice, and tie is inspected. When the caissons are poured, concrete samples are taken and tested for compressive strength after 28 days. Only once those results are verified can you move forward with the next phase of construction.

For the client, all this foundational work can be frustrating. It’s slow, noisy, expensive, and at the end of the long process, it’s invisible. You spend months on permits, soils tests, excavating, and inspections, and when it’s done, the homeowner sees nothing but flat dirt. That’s why setting clearexpectations is crucial.

I tell my clients: this is not like building a pool in the flatlands. It’s a process measured in months, not weeks, and most of what you’re paying for will never be seen. But it is nonetheless the difference between a pool that will last a lifetime and one that could literally slide down the hill.

The Price of Professionalism

The cost of doing things right on a hillside is not trivial. Crane rentals can easily run $3,000 a day, and engineering and soils oversight are mandatory. Liability insurance can exceed $50,000 per year for companies that perform below-grade work, shortcuts or cutting corners is never an option.

Every subcontractor must be properly licensed and insured, and everyone on site must be trained and equipped for safety. It’s not uncommon to see smaller contractors try to take on hillside projects without the right team or experience. That’s a recipe for disaster. I tell homeowners: if your contractor doesn’t have hillside experience and a solid safety record, walk away.

Building a hillside pool in Los Angeles requires engineered precision and patience. The process demands communication between the builder, architect, engineer, soils consultant, and city inspector at every step. There’s no room for improvisation or last minute changes.

And yet, when the dust settles and the forms come off, what remains is a structure rooted deep in the earth—strong, invisible, and permanent. The client sees a tranquil pool, maybe a vanishing edge looking over the canyon, and never thinks about the tons of steel and concrete below or the planning and effort that went into creating those unseen structures.

That’s how it should be.

Note: the pictured project will be profiled in upcoming WaterShapes editions.

JC Escudero is co-founder and CEO of J Designs Pool & Spa a custom swimming pool design and construction company based in North Hollywood, CA. With extensive experience in structural pool construction, hillside engineering, and project management, he has built a career at the intersection of precision, safety, and design integrity in some of Southern California’s most challenging environments.