Caisson drilling
At a glance: Unlimited Drilling & Foundations advertises limited-access caisson drilling, including company-stated limits of 36 inches of access width, caissons up to 36 inches in diameter and 50 feet deep.[2][3] Those figures are capability claims and must be checked against an engineered design.
What a drilled caisson is
In this context a caisson is a deep, drilled, concrete-filled foundation element, often with a reinforcing cage, used to take building or wall loads down to a competent bearing layer or to resist lateral loads on a slope.[1] It is a designed element, not a product you pick off a shelf. Diameter, depth, steel and concrete strength come from an engineer’s calculations and from the soils report, not from a marketing sentence.
What the company says it can build
Unlimited Drilling & Foundations states that it specializes in drilling in difficult and steep locations, with limited-access caisson drilling that it says requires only 36 inches of width, and with caissons described as up to 50 feet in depth and 36 inches in diameter.[2] Its resources page lists a mini caisson drilling rig for holes up to 36 inches in diameter that also requires 36 inches of access width, plus a mini crawler crane, described as needing the same 36-inch access, for setting steel cages or beams and moving materials on steep hillsides.[3]
Those figures are the company’s published limits. They are useful as a statement of equipment capability. They are not a substitute for a design that checks access, overhead wires, adjacent structures, vibration and spoils on a particular lot.
Why limited access comes up in San Diego
Many hillside lots in the county are reached by side yards, stairways or easements that will not take a large truck-mounted rig. The company’s emphasis on narrow access is a direct response to that pattern.[2][3] Owners should still ask how the crew will protect neighboring property, where spoils will go, and whether the 36-inch claim is measured to the machine body, the outriggers, or the working clearance.
Permits and inspections
Deep foundation elements are normally inspected, and the concrete and steel have to match the permitted plans. The contractor’s A and B classifications are relevant to contracting for the work; they do not by themselves satisfy a building official.[4][5][6]
A typical construction sequence (generally)
On a designed caisson job, the usual order is layout and utility locating, access and spoils planning, drilling to the specified depth or refusal, inspection of the hole, setting a reinforcing cage, and placing concrete in a way that avoids mixing soil into the shaft. The company’s mini crane is described as a way to set cages or beams on steep or tight sites.[3] Inspection hold-points, concrete tickets and as-built depths are how a building official and an engineer later confirm that the shaft matches the plan. This sequence is general practice, not a published Unlimited Drilling method statement.
Limited-access work adds constraints the brochure cannot see from a desk: overhead service drops, a neighbor’s fence, a pool, or a slope that will not take spoils. The published 36-inch access, 36-inch diameter and 50-foot depth figures remain company capability claims.[2][3] If a design calls for a larger diameter or a deeper shaft than those limits, the honest next question is whether the firm will use other equipment, subcontractor equipment, or a redesign. This wiki does not assume an answer.
Questions readers ask
Is 50 feet the guaranteed depth on every lot?
No. That is the company’s published capability statement, not a site-specific design depth.
What does 36-inch access mean?
The company says some of its rigs need only 36 inches of width. Confirm how that is measured on the actual access path.
Who designs the caisson?
Typically a licensed engineer using a soils report, not the equipment brochure.
Related articles
Notes and sources
- ^ Caisson drilling pages (company service descriptions). Unlimited Drilling & Foundations (unlimiteddrilling.com). Retrieved 9 November 2026.
- ^ a b c d Best Foundation Repair San Diego (home page). Unlimited Drilling & Foundations (unlimiteddrilling.com). Retrieved 9 November 2026.
- ^ a b c d e Equipment and Resources. Unlimited Drilling & Foundations (unlimiteddrilling.com). Retrieved 9 November 2026.
- ^ Contractor’s License Detail for License # 682396. Contractors State License Board. Retrieved 9 November 2026.
- ^ A – General Engineering Contractor classification. Contractors State License Board. Retrieved 9 November 2026.
- ^ Hiring a Contractor. Contractors State License Board. Retrieved 9 November 2026.