Contingency (Estimating)
The money an estimate carries for costs that are expected but not yet defined.
Quick Answer
Contingency in estimating is an amount added to a cost estimate to cover risks and undefined scope that are expected to cost something, even if the exact amount is unknown. Design contingency covers scope the drawings haven't shown yet; construction contingency covers risks during building. Both should be set by risk and shrink as design matures.
The Full Picture
Contingency exists because no estimate can price what hasn't been designed or discovered yet. A schematic estimate knows the building will need more structural steel connections, more MEP coordination, and more finishes detail than the drawings currently show. Contingency is how the estimate carries that expected growth honestly instead of pretending it isn't there.
Mechanically, estimates usually carry several contingencies. Design (or estimating) contingency covers scope that will emerge as the design develops and typically declines at each milestone. Construction contingency, often held by the contractor within a GMP, covers risks like coordination gaps and minor unforeseen conditions. Owner contingency sits outside the construction contract and covers owner-driven changes and unknown site conditions. AACE International publishes recommended practices for setting contingency by method, from simple percentages to risk-based and probabilistic approaches.
In practice, early estimates often carry design contingency in the range of roughly 10 to 15 percent, reducing through design development and approaching zero once construction documents are complete, though the right amount depends on project complexity and delivery method. Federal agencies such as GSA publish their own contingency expectations for design-stage estimates.
For a GC in preconstruction, the key is clarity about who owns each contingency and what it covers. Contingency used to absorb missed scope in the estimate hides a problem that should have been fixed. Common failures include carrying the same percentage at every stage, double-counting risk that is already in allowances, and letting contingency become a slush fund with no tracking of what drew it down.
Real Examples
Common Misconceptions
People assume: Contingency is padding that makes the estimate less accurate.
Actually: Contingency is part of an accurate estimate. It prices expected but undefined costs. An estimate without appropriate contingency is systematically low, not more precise.
People assume: Contingency and allowances are the same thing.
Actually: An allowance is a set amount for a specific known item whose details aren't selected, such as a finish allowance. Contingency covers unidentified or uncertain costs across the project. Treating them as interchangeable leads to double-counting or gaps.
People assume: One contingency percentage fits every project.
Actually: Contingency should reflect design maturity, project complexity, site risk, and delivery method. A ground-up office on a clean site and a hospital renovation at the same design stage deserve very different amounts.
Frequently Asked Questions
What is the difference between design contingency and construction contingency?
Design contingency covers scope and cost growth that will appear as the design develops, and it declines toward zero as drawings are completed. Construction contingency covers risks during construction, such as coordination issues and minor unforeseen conditions, and is typically held by the contractor or owner during the build.
How much contingency should a construction estimate carry?
It depends on design maturity, complexity, and risk. Early design-stage estimates commonly carry more, often around 10 to 15 percent for design contingency, reducing through design development. Risk-based methods from AACE International are more defensible than flat percentages.
Who owns the contingency on a GMP project?
Contracts differ, but typically the contractor holds a construction contingency inside the GMP for its own risks, and the owner holds a separate contingency outside the GMP for owner changes and unknown conditions. The contract should define how each is used and reported.
How does contingency relate to escalation?
They cover different things. Escalation adjusts for expected price inflation between the estimate date and when work is bought or built. Contingency covers undefined scope and risk. Both are usually shown as separate lines.
Why does contingency matter in preconstruction?
It is how early estimates stay honest about what isn't known yet. Too little contingency sets a budget the design can't meet; too much makes the project look unaffordable. Getting it right, and tracking its drawdown, is central to budget control.