Foundation Overrun Calculator

Foundation overruns crush budgets. This calculator sizes risk.

Foundation budget

Deep foundation probability %

Deep foundation premium

Concrete escalation %

Rebar escalation %

Total overrun risk

$477,000

Deep foundation expected

$117,000

Material escalation

$360,000

How the math works

Deep expected = probability × premium. Material = budget × blended escalation. Total = both.

Run a pre-construction geotechnical review when the site design is ~60% complete. Identifying deep-foundation requirements at that stage allows redesign of the superstructure to shift load distribution — cheaper than discovering it at mobilization when schedule and sub commitments are locked.

How to Use

Enter foundation budget.
Enter deep foundation upgrade probability %.
Enter deep foundation premium $.
Enter concrete cost escalation %.
Enter rebar cost escalation %.
Read total overrun risk.

Frequently Asked Questions

Shallow vs deep?

Shallow (spread footing, mat): $30-80/SF bldg footprint. Deep (piles, piers, caissons): $80-250/SF. Switching from shallow to deep based on soil findings = 2-3x cost. Geotech report critical.

Material escalation?

Concrete 2021-2024: 15-35% cumulative. Rebar: 40-80% cumulative. Budget with escalation contingency especially on long-lead projects. Concrete supply shortages during boom add 1-3 month delays.

Mitigation?

Pre-order rebar at contract price. Concrete contract with index tie-in. Alternative foundation schemes pre-designed if soil surprises. Geotechnical contingency budget separate from GC contingency.

How often should I rerun this?

Rerun this calculator whenever inputs change materially — new rent roll data, rate moves, loan balance updates, or quarterly operating data. For active deals, monthly refresh is typical. For stabilized assets under monitoring, quarterly is fine. Treat the output as a decision tool, not a one-time answer — market conditions evolve and so should your analysis.