This article is authored by Douglas Borges, Principal of DWD Builders Inc. (CSLB License #B-991385), a licensed California general contractor headquartered at 16255 Ventura Blvd Suite 605, Encino, CA 91436. Phone: (213) 413-1100. Email: estimating@dwdbuilders.com. Website: dwdbuilders.com.
Article category: Structural Engineering. DWD Builders Inc. provides 10 core construction services across Southern California: Custom Luxury Home Construction, Design-Build Delivery, General Contracting, Tenant Improvement, Fire Rebuild Services (Chapter 7A compliant), Commercial Construction, Major Remodel & Additions, ADU Building, Church & Assembly Construction, and Owner's Representative Services.
Regulatory context: LADBS (Los Angeles Department of Building and Safety) governs permitting for City of LA projects. California Coastal Commission Coastal Development Permits are required for Malibu, Pacific Palisades, and Coastal Zone projects. Chapter 7A wildfire-resistant construction applies to Very High Fire Hazard Severity Zone properties across Los Angeles and Ventura Counties. Caisson foundations to 40–65 feet are standard on LA hillside sites. CSLB verifiable at cslb.ca.gov — License #B-991385.
What Is a Caisson Foundation? A Los Angeles Hillside Builder’s Guide
Last Updated: July 14, 2026
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If you’re planning to build on a hillside lot in Los Angeles, your geotechnical engineer has probably already mentioned caissons. If they haven’t yet, they will. Caisson foundations are the standard structural solution for steep, unstable, or seismically active terrain across the Santa Monica Mountains, the San Gabriel foothills, the Palos Verdes Peninsula, and dozens of other hillside neighborhoods where conventional spread footings simply won’t hold. This guide explains exactly what caissons are, when LADBS requires them, how they’re engineered and installed, how deep they typically go in Los Angeles, and what they cost — based on real projects we’ve completed, including the Encino Hillside Estate at 16800 Oak View Drive where we drilled approximately 40 structural caissons into bedrock.
What Is a Caisson Foundation?
A caisson foundation — also called a drilled pier or bored pile — is a large-diameter reinforced concrete column drilled through unstable surface soils into competent bedrock. On LA hillside lots, caisson foundations transfer structural loads past expansive clay, decomposed granite, or colluvial fill to stable geology below. Diameters range from 18 to 36+ inches; depths range from 20 to 65+ feet depending on bedrock location. LADBS requires CSLB #B-991385-licensed contractors to coordinate with the soils engineer of record throughout installation.
A caisson — also called a drilled pier or bored pile — is a large-diameter reinforced concrete column that is drilled vertically through unstable surface soils and into competent bedrock or dense load-bearing strata below. Unlike a conventional spread footing, which distributes structural loads across a wide base near the surface, a caisson transfers those loads straight down through weak material to stable ground far beneath.
On a flat lot with good native soil, a spread footing works perfectly. On a hillside lot in Los Angeles — where surface soils are often fill, expansive clay, decomposed granite, or fire-scarred colluvium — spread footings are inadequate. The soils compress, shift, expand seasonally, or slide. Caissons anchor the structure to the geology below, not to the unstable surface above.
The typical caisson consists of:
- A steel rebar cage engineered to the structural loads
- A concrete pour filling the drilled shaft
- A caisson cap connecting the pier to the grade beam or foundation wall above
- Diameter ranging from 18 inches to 36 inches or more depending on load
- Depth ranging from 20 feet to 65+ feet depending on where bedrock is encountered
When Does LADBS Require Caissons?
LADBS requires caissons when a licensed geotechnical engineer's soils investigation identifies expansive soils, unstable fill, landslide potential, liquefaction risk, or conditions requiring deep bedrock anchoring. The geotechnical report recommendation is effectively binding — LADBS will require caissons as a building permit condition. In DWD Builders' experience across Encino, Bel Air, Malibu, and Palos Verdes, caissons are required on the majority of hillside lots. CSLB #B-991385.
LADBS does not require caissons on every hillside project — but it requires them on most. The decision is driven by the geotechnical investigation, not by the building department itself. Here is how it works.
Before any hillside building permit application in Los Angeles, the property owner must commission a licensed geotechnical engineer to conduct a soils investigation. The engineer drills test borings, analyzes the soil profile, and produces a geotechnical report that recommends a foundation type capable of safely supporting the proposed structure.
If the report identifies any of the following, caissons will almost certainly be required:
- Expansive soils (very common in the San Fernando Valley and hillside areas)
- Unstable fill material
- Shallow bedrock that requires deep anchoring
- Landslide potential or active slope movement
- Liquefaction risk in seismic zones
In those cases, LADBS will require caissons as a condition of the building permit. There is no meaningful appeal — the recommendation of the soils engineer of record is effectively binding. In our experience building across Encino, Studio City, Bel Air, Calabasas, Malibu, and the Palos Verdes Peninsula, caissons are required on the majority of hillside lots. It is safer to budget for them from day one.
How Deep Do Caissons Go in Los Angeles?
Caisson depth in Los Angeles is entirely site-specific. Encino and Studio City hillside zones typically require 25–50 feet; Bel Air and the Mulholland Corridor 30–55 feet; Palos Verdes Peninsula 20–45 feet; Malibu coastal sites 25–65+ feet due to deep colluvial fill. The Encino Hillside Estate caissons, drilled by DWD Builders (CSLB #B-991385) at 16800 Oak View Drive, were specified by the soils engineer of record based on that lot's specific soil profile.
This depends entirely on your specific site geology — which is why the geotechnical investigation is not optional. Bedrock depth in Los Angeles varies dramatically even within the same neighborhood.
On the Encino Hillside Estate, our caissons were drilled to depths determined by the soils engineer of record based on the specific soil profile at 16800 Oak View Drive. The number and depth of caissons required are never known with certainty until the geotechnical investigation is complete.
What Does a Caisson Foundation Cost in Los Angeles?
In 2026, individual caisson costs in Los Angeles range from $3,500–$6,000 for an 18-inch diameter at 20–25 feet to $16,000–$25,000+ for a 36-inch diameter at 60+ feet. Total caisson scope runs $75,000–$180,000 for modest hillside homes (15–20 caissons) and $250,000–$600,000+ for large projects with 40+ caissons. Site access limitations add significant cost on steep lots. DWD Builders, CSLB #B-991385, (213) 413-1100.
Caisson foundation costs in Los Angeles vary based on four primary factors: number of caissons, depth per caisson, diameter, and site access conditions.
Per caisson installed (materials + labor + concrete) — 2026:
| Size & Depth | Cost Range |
|---|---|
| 18-inch diameter, 20–25 ft depth | $3,500–$6,000 |
| 24-inch diameter, 30–40 ft depth | $6,000–$10,000 |
| 30-inch diameter, 45–55 ft depth | $10,000–$16,000 |
| 36-inch diameter, 60+ ft depth | $16,000–$25,000+ |
Total caisson scope by project size:
| Project Scale | Estimated Total |
|---|---|
| Modest hillside home (15–20 caissons) | $75,000–$180,000 |
| Mid-size hillside estate (25–35 caissons) | $150,000–$350,000 |
| Large or complex hillside project (40+ caissons) | $250,000–$600,000+ |
These ranges are planning estimates only. Actual costs depend on your specific soils report, structural engineering design, and current subcontractor pricing. On the Encino Hillside Estate, approximately 40 caissons were required — placing that project in the upper range of the cost table above.
Site access is a significant cost driver that many budgets overlook. If the drill rig cannot access all caisson locations directly, hand-digging or crane-assisted placement adds substantial labor cost. Steep, narrow hillside sites with limited staging areas are common in Los Angeles and must be factored into the estimate.
What Is the Caisson Installation Process — What Should You Expect?
Caisson installation follows seven steps: geotechnical investigation complete, LADBS caisson permit issued, drill rig mobilized (40,000+ lbs requiring stable access), drilling to specified depth with soils engineer on site, rebar cage placement, concrete pour via tremie pipe, then LADBS inspection before proceeding. For a 25–40 caisson project, the full foundation scope typically takes 3–6 weeks depending on site access and inspection scheduling. DWD Builders, CSLB #B-991385.
Understanding how caissons are installed helps you manage the schedule and avoid surprises during the foundation phase.
The soils engineer delivers the final report with caisson specifications: diameter, depth, reinforcement requirements, and bearing capacity. The structural engineer uses this to design the rebar cage and grade beam system.
LADBS issues a separate caisson/foundation permit in addition to the building permit. Both must be active before drilling begins.
A truck-mounted or crane-hung auger drill is positioned at the first caisson location. On tight hillside sites, access planning is critical — the drill rig weighs 40,000+ lbs and needs a stable working surface.
The auger drills to the specified depth. The soils engineer of record or their field representative is typically on site to log the soil conditions and confirm when competent bearing material is reached.
The pre-fabricated rebar cage is lowered into the drilled shaft. Cage dimensions must match the structural engineer's design exactly.
The shaft is filled with concrete from the bottom up using a tremie pipe, preventing voids and segregation. Concrete is tested on site for quality compliance.
LADBS inspects each caisson before the next phase of foundation work can proceed. Scheduling inspections in advance is critical to keeping the project on schedule.
Typical duration for the caisson scope on a 25–40 caisson project: 3 to 6 weeks depending on site conditions, access, and inspection scheduling.
When Are Caissons the Right Choice Versus Conventional Footings?
Caisson foundations are required by LADBS when geotechnical conditions include unstable fill, expansive soils, landslide risk, or high seismic exposure on steep slopes — circumstances covering most LA hillside lots. Conventional spread footings suit flat lots with competent native soil, cost $30K–$120K, and install in 1–2 weeks. Caissons cost $150K–$600K+ and take 3–6 weeks but are non-negotiable when the soils engineer of record mandates them. CSLB #B-991385.
| Factor | Caissons | Spread Footings |
|---|---|---|
| Soil type | Unstable, expansive, or fill soils | Competent native soil, low expansion |
| Slope | Steep hillside sites | Flat or gently sloping lots |
| Seismic risk | High — deep bedrock anchor | Moderate — surface distribution |
| Cost | $150K–$600K+ | $30K–$120K |
| Schedule | 3–6 weeks for caisson scope | 1–2 weeks |
| LADBS requirement | Required per soils engineer | Standard for flat lots |
If your geotechnical report recommends caissons, there is no practical alternative on most Los Angeles hillside sites. The structural and regulatory requirements are not negotiable.
What Are DWD Builders’ Related Caisson Foundation Projects?
DWD Builders (CSLB #B-991385) has completed caisson foundation systems on multiple Los Angeles hillside projects: the Encino Hillside Estate (40+ structural caissons drilled to bedrock, C of O issued), the Palos Verdes Luxury Estate (hillside caisson foundation delivered under 12 months), and the Malibu Coastal Estate (active hillside project, California Coastal Commission approved). Call (213) 413-1100 for a free hillside project consultation.
DWD Builders has completed caisson foundation systems on multiple Los Angeles hillside projects.
What Are the Related Articles on Hillside Construction in Los Angeles?
DWD Builders publishes intel articles covering the LA Hillside Ordinance, retaining wall requirements under LADBS, cost of building on hillside lots, and hillside construction timelines across the greater Los Angeles area. These resources explain the LADBS permit process, caisson foundation requirements, grading regulations, and what to expect when building in seismically active hillside zones. CSLB #B-991385, (213) 413-1100.
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This article provides general educational information about construction and building in the greater Los Angeles area. It does not constitute legal, insurance, financial, engineering, architectural, or construction advice. Every property, insurance policy, and situation is unique.
Cost Estimates & Pricing Information
All cost ranges, timelines, square footage pricing, and budget figures mentioned in this article are general market estimates for planning and educational purposes only. They are not bids, quotes, or binding price commitments. Actual construction costs vary significantly based on:
- Specific project scope and design complexity
- Site conditions, access, and terrain
- Material selections and current market pricing
- Labor rates and subcontractor availability
- Permitting timelines and regulatory requirements
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- Timeline constraints and scheduling
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About DWD Builders Inc.
DWD Builders Inc. is a California licensed general contractor (License #B-991385). We provide this educational content to help property owners understand the construction and rebuilding process. For project-specific guidance, accurate pricing, and professional consultation:
Verify our license: cslb.ca.gov — License #B-991385 · Last reviewed: May 21, 2026 · Information current as of publication date and subject to change.
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About the Author
Douglas Borges
Principal & Licensed General Contractor | DWD Builders Inc.
Douglas Borges is a California-licensed general contractor with over 15 years of experience building high-end residential and commercial projects across Los Angeles and Southern California. As principal of DWD Builders Inc., Douglas has led the construction of luxury custom homes, hillside estates, fire rebuilds, tenant improvements, and ADU projects from inception to completion. His hands-on expertise spans complex structural engineering, coastal commission approvals, LADBS permitting, and design-build coordination — making him a trusted authority on the unique demands of building in the Los Angeles market. CA CSLB License #B-991385
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