Contingency should reflect the design, contract, site, pricing certainty, and unresolved scope—not a percentage pasted onto every project.
Start with the uncertainty register
Before choosing a contingency percentage, list the unresolved items: incomplete plans, unselected finishes, unknown soil or rock, utility distances, allowance exposure, price escalation, renovation discovery, long-lead substitutions, and work outside the main contract.
A project with complete construction documents, fixed selections, tested site conditions, and a clear fixed-price contract carries different uncertainty than an early design with broad allowances and acreage site work.
Do not use contingency to hide scope
If a pool is planned, show a pool budget. If the utility run is expected, carry an allowance for the run. If landscaping is required by the development, include it. Known work belongs in the base budget even when the final bid is pending.
Keep an owner-upgrade list separate. Upgrades are choices. Contingency is capacity for project risk. Mixing them makes it impossible to know whether the build is actually staying on budget.
Set the control rules
Decide who can authorize use of contingency, what documentation is required, whether unused funds can cover owner changes, and how a change affects the draw schedule and appraisal scope. Those decisions should be consistent with the contract and lender process.
The right contingency is the amount the documented risk supports and the financing structure accepts. It should be discussed with the builder, lender, and appropriate construction advisers—not selected because another project used the same percentage.