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24in.
Diameter of the Type P1 caissons on our Macapa Drive hillside project
12ft
Minimum embedment into bearing material on that schedule
$800–1,500+
Per linear foot of drilled caisson, Los Angeles market range
Aggregate Construction Group, 2026
160lin. ft
What a schedule of eight caissons at 20 feet each adds up to. You pay by depth, not by unit.
Caisson Foundations · Los Angeles Hillside
The part of the house you never see is the part holding it up.
Drilled caisson foundations for steep Los Angeles lots, explained by the contractor who builds them. If you own a steep lot in Los Angeles, someone has said the word to you and moved on. A caisson, also called a drilled pier, is a reinforced concrete column bored down through the loose surface soil until it reaches material strong enough to carry a house. On a hillside the top layer often cannot support a building, and worse, it can move. Caissons skip that layer and hand the load to bedrock below.
Loose surface soilBedrockCaissons and grade beamSwipe sideways for the whole drawing.
Hover a step to see that part alone. The downhill caissons are longer, because bedrock is deeper there. That is why caisson cost is quoted per linear foot rather than per pier, and why the same house costs more on the steeper side of the street.
How it gets designed
Nobody chooses caissons from a catalogue. The design comes out of the ground.
01
The geotechnical report comes first
A geotechnical engineer bores the site, identifies the soil profile, locates competent bearing material and issues the report. That document sets bearing capacity, required embedment, minimum diameter, spacing and setback from the slope face. Every number in the foundation traces back to it.
02
The structural engineer sizes the system
Working to the geotechnical findings and the building loads, the structural engineer produces a pile schedule: a table defining each caisson type by diameter, depth, reinforcement and embedment. On our Macapa Drive project the schedule specified five new Type P1 caissons, 24 inches in diameter, minimum 12-foot embedment, carrying the downhill addition.
03
Grade beams tie it together
Individual caissons are connected at the top by reinforced concrete grade beams, which spread load between them and give the structure a continuous bearing surface. Caissons and grade beams are one system. Neither works alone.
04
We read the schedule against the plan
A pile schedule can define a type that never appears on the foundation plan. We check the schedule against the plan sheet before anyone mobilizes a rig. A discrepancy found in the drawings costs a phone call. The same discrepancy found in the field costs a week.
Drilling, placing, inspecting
What happens on site
Drilled cast-in-place means the hole is bored, the steel cage is lowered in and concrete is placed on site. Driven piles, hammered in pre-formed, are rarely practical on a tight residential hillside. The constraint people underestimate is access. The rig has to physically reach every caisson location.
Access decides the method
Rig size, staging area and concrete delivery are set by the street, not by the drawings. We assess access before we price the foundation, because on hillside sites it is often the difference between two bids.
Special inspection, every step
Deep foundation work in Los Angeles is observed and recorded as it proceeds: drilling depth, bearing material, reinforcement placement, concrete placement. Those records matter at final sign-off and again the day the house is sold.
Then the ground is ready
Grade beams tie the caissons into a single system, inspections are cleared and documented, and the site hands off to structure.
A worked example. Eight caissons at 20 feet each is 160 linear feet. At the published Los Angeles range of $800 to $1,500 per linear foot, that is $128,000 to $240,000 before the grade beams, and before anyone has moved a rig up your street.
What caissons cost
Three things move the number more than anything else
How deep competent bearing material sits. How many caissons the structural design requires. Whether a rig can reach each location without extraordinary measures. None of the three can be answered before the soils report exists, which is why any foundation price quoted without one is a guess.
Drilled caissonsper linear foot of total drilled depth, Aggregate Construction Group, 2026
$800 – $1,500+
Slope premium over a flat-lot buildwhole project, Aggregate Construction Group, 2026
20 – 35%
High-end custom with hillside complexityper square foot, Energize Builders projects
$700 – $1,000+
$500,000 minimum
Caisson work is one part of a hillside project. We take on the whole project, from soils report to sign-off, at or above that number.
Before you call
What owners ask us about caissons
Short answers here. Longer ones on the phone, with your soils report in front of us.
What is a caisson foundation?
A drilled, reinforced concrete column that carries a building's load down through loose surface soil to competent bedrock. On Los Angeles hillsides the top layer often cannot support a house and can move; caissons skip it and bear on rock. They are tied together at the top by grade beams, and the two work as one system.
How deep do caissons go?
As deep as competent bearing material sits, plus the embedment the geotechnical engineer requires. On our Macapa Drive project the schedule called for 24-inch Type P1 caissons with a minimum 12-foot embedment. Downhill caissons are usually longer than uphill ones, because bedrock is deeper there.
How much do caissons cost?
Published Los Angeles ranges run $800 to $1,500 and up per linear foot of drilled depth (Aggregate Construction Group, 2026). Eight caissons at 20 feet is 160 linear feet, or roughly $128,000 to $240,000 before grade beams. Depth, count and access move that number, and none of the three is known before the soils report.
Does every hillside house need caissons?
No. The geotechnical report decides. Some sites bear on shallow rock with conventional footings; many need caissons under the downhill side only; steep or slide-prone lots need them throughout. Anyone who tells you the answer without a soils report is guessing.
What is the difference between a caisson and a pile?
A caisson, or drilled pier, is bored and poured in place. A driven pile is hammered in pre-formed. On a tight residential hillside the drilled method is almost always the practical one, because the rig can reach each location and the work is quieter and more controlled.
Who inspects the work?
Deep foundation work in Los Angeles is performed under special inspection: drilling depth, bearing material, reinforcement placement and concrete placement are observed and recorded as they happen. Those records are part of final sign-off and part of the house's file when it sells.
Where we build
Pacific Palisades, and the hills around it
Pacific Palisades is rebuilding lot by lot, and many of those lots are steep. If yours is one of them, or you are on a slope anywhere from Malibu to Calabasas, send us the soils report.
Hillside construction in Los AngelesThe full service: retaining and shoring, Baseline Hillside Ordinance permitting, grading and the build itself.
- Pacific Palisades
- Malibu
- Bel Air
- Beverly Crest
- Beverly Hills
- Hollywood Hills
- Mandeville Canyon
- Brentwood Hills
- Sherman Oaks Hills
- Encino Hills
- Hidden Hills
- Calabasas
Start here
Got a soils report? Send it over.
If you have a geotechnical report, a pile schedule, or a lot you are not sure about, send it to us. We will tell you what it means and what it is likely to cost before you commit to anything.
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