Drilled Shaft (Caisson) Cost Guide 2025
Pricing for drilled shaft construction — commercial, infrastructure, and high-rise applications.
Drilled shafts (also called caissons, drilled piers, or bored piles) are the foundation of choice for high-rise buildings, bridges, and heavy infrastructure. Costs range from $100 per linear foot for small-diameter shafts in favorable soil to over $1,500 per linear foot for large-diameter shafts in difficult rock. A single drilled shaft for a high-rise building can cost $50,000–$500,000+. This guide provides detailed cost breakdowns for the full range of drilled shaft applications.
Cost Ranges
| Item | Low Range | High Range | Notes |
|---|---|---|---|
| Small shaft (18–24" dia, soil, 30–60 ft) | $100/LF | $250/LF | Light commercial, residential. Total $3,000–$15,000 per shaft. |
| Medium shaft (36–48" dia, soil/rock, 40–80 ft) | $200/LF | $600/LF | Commercial buildings, bridges. Total $10,000–$50,000 per shaft. |
| Large shaft (60–96" dia, rock socket, 60–150 ft) | $500/LF | $1,500/LF | High-rise, major bridges. Total $50,000–$225,000 per shaft. |
| Mobilization (large drill rig) | $50,000 | $200,000 | Crane-mounted rigs. Higher for barge-mounted marine work. |
| Load testing (O-Cell or top-down) | $50,000 | $300,000 | Per test. O-Cell (Osterberg) is standard for large shafts. |
| CSL integrity testing | $2,000 | $5,000 | Per shaft. Cross-hole sonic logging. Required on most projects. |
Factors That Affect Cost
Shaft Diameter
Cost increases roughly with the square of diameter. 36" shaft costs ~4x more per foot than 18" shaft.
Depth
Deeper shafts require more concrete, steel, casing, and drilling time. Very deep shafts (>100 ft) require specialized equipment.
Soil vs. Rock Drilling
Rock drilling costs 2–5x more per foot than soil drilling. Hard rock (granite, gneiss) is most expensive.
Casing Requirements
Full-depth permanent casing adds $50–$200/LF. Required in caving soils or through water-bearing zones.
Concrete Volume
Large shafts consume enormous concrete volumes. A 10-ft diameter, 100-ft deep shaft needs ~580 cubic yards.
Reinforcement
Heavy rebar cages for seismic or high-load applications can cost $50,000–$200,000 per shaft.
Integrity Testing
CSL testing ($2,000–$5,000/shaft), thermal integrity ($3,000–$8,000/shaft). Required on most projects.
Spoils Disposal
Contaminated spoils disposal can add $50–$200/CY to project cost.
Money-Saving Tips
- Optimize shaft diameter and length through thorough geotechnical investigation — over-conservative design wastes money
- Consider O-Cell load testing to verify capacity and potentially reduce shaft dimensions on large projects
- Allow contractor flexibility on construction sequence to maximize rig productivity
- Evaluate permanent vs. temporary casing — temporary casing saves material cost where soil allows
- Bundle drilled shaft work with other foundation elements for better mobilization economics
- Schedule rock drilling during dry season when groundwater is lowest
Frequently Asked Questions
How much does a drilled shaft cost for a house?
Residential drilled shafts (18–24 inch diameter, 20–40 feet deep) typically cost $3,000–$10,000 per shaft installed. A typical home might need 4–8 shafts, totaling $15,000–$60,000 for the foundation. This is common in areas with expansive soils (Colorado, Texas) where shallow foundations fail.
Why are drilled shafts so much more expensive than driven piles?
Drilled shafts require larger, more expensive equipment (crane-mounted drill rigs vs. pile driving hammers), produce spoils that must be disposed of, use large volumes of concrete and reinforcing steel, and have slower production rates (1–3/day vs. 10–30/day for driven piles). However, each shaft carries much more load, so fewer are needed.
What is an O-Cell load test and why is it so expensive?
An O-Cell (Osterberg Cell) test embeds a hydraulic jack at the bottom of the shaft that pushes against both the base and the shaft simultaneously. It's the only practical way to test very high-capacity shafts (>1,000 tons) because conventional top-down tests would require enormous reaction systems. The cost ($100,000–$300,000) includes the sacrificial test shaft, instrumentation, and analysis.
Can I use drilled shafts instead of a full basement?
Yes — in expansive soil areas (Colorado, Texas), drilled shafts with grade beams and a structural floor slab (void form system) are the standard residential foundation. This eliminates the basement but provides a stable foundation that resists soil movement. Cost is typically $20,000–$60,000 for a typical home.