Sitework Overrun Calculator

Sitework overruns blow budgets. This calculator sizes typical overrun probability.

Sitework budget

Soil risk %

Utility conflict %

Weather risk %

Contingency held %

Net overrun exposure

$280,000

Total risk %

25.00%

Contingency held

$420,000

How the math works

Total risk = sum of risks. Net exposure = risk dollars − contingency.

Before committing to a sitework budget, invest $15-40k in geotechnical, environmental, and utility survey work. That pre-investment typically reveals the 60-80% of discovered conditions that become change orders — much cheaper to design around than to blast through.

How to Use

Enter sitework budget.
Enter unknown soil risk %.
Enter utility conflict risk %.
Enter weather delay risk %.
Enter contingency held %.
Read probability-weighted overrun.

Frequently Asked Questions

Typical overruns?

Clean sites (agricultural, greenfield): 5-15% overrun. Infill sites (urban, previously developed): 15-40%. Contaminated sites: 40-150%. Rocky or high-water-table sites: 20-60%. Soils report is the best early warning.

Hidden drivers?

Undocumented utility lines (cost to relocate + delay). Rock excavation (blast or hammer costs 5-10x regular). Groundwater (dewatering $5-50k/month). Archaeological findings (full site stop). Each is catastrophic when not identified.

Contingency?

15-25% sitework contingency is market standard. Complex sites: 25-40%. Brownfield/redevelopment: 40-60%. Under-contingent bids lose first to change orders, second to discovered conditions.

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.