Differing Site Conditions
A contract clause and common-law doctrine addressing unforeseen physical conditions at a site that differ materially from what the contract documents indicated, or from what a contractor could reasonably have anticipated, entitling the contractor to an equitable adjustment rather than absorbing the extra cost itself.
Why it matters
The doctrine only protects a contractor who gives timely written notice once the condition is discovered. A genuinely differing condition can still go uncompensated if the contractor keeps working without flagging it formally first.
On a real project
A contractor's boring logs show sandy soil throughout a site, but excavation hits solid rock across a third of the foundation footprint, a materially different condition than what the contract documents represented, supporting a differing site conditions claim.
Who this matters most to
A Construction Claims Consultant investigates whether an encountered condition actually differs materially from what the contract documents represented, the technical basis the whole claim depends on.
Where this goes wrong
A contractor's crew strikes an unmapped high-pressure gas line during excavation, well outside where the utility drawings placed it, but the superintendent handles the relocation informally in the field without submitting the written notice the differing site conditions clause requires. By the time a formal claim is filed, the contractor has lost the right to an equitable adjustment even though the condition was genuinely differing.