An unforeseen site conditions claim is how a contractor recovers additional cost and time when the ground, the structure, or the surroundings turn out to be materially different from what the contract described or from what the trade would reasonably expect. Federal projects run the claim through FAR 52.236-2, and most private commercial work runs it through AIA A201, Section 3.7.4. Both recognize two categories of differing site conditions, both demand prompt written notice, and both pay only the contractor who kept good records and kept working.
Which Type of Condition You Have
The category matters because it determines what you have to prove.
A Type I condition is one that contradicts the contract documents. The federal clause defines it as “subsurface or latent physical conditions at the site which differ materially from those indicated in this contract.”1Acquisition.gov. 48 CFR 52.236-2 – Differing Site Conditions A geotechnical report characterized the soil as loose and sandy; you hit solid granite. The gap between the representation and the reality is the claim. Type I requires that the contract or an associated report made an affirmative representation about site conditions and that you reasonably relied on it when bidding.
A Type II condition does not depend on any specific document being wrong. It is a physical circumstance “of an unusual nature, which differ[s] materially from those ordinarily encountered and generally recognized as inhering in work of the character provided for in the contract.”1Acquisition.gov. 48 CFR 52.236-2 – Differing Site Conditions A buried fuel tank or an undocumented utility line on a suburban building site is the classic example. The standard is what a reasonably experienced contractor in that trade would expect, not what you personally expected.
Either way, the difference has to be material. The discovery must genuinely drive up cost or time; a minor variance from the drawings does not qualify.
Whether a Site Visit Should Have Caught It
Before an owner will entertain a claim, the first question is whether a reasonable pre-bid inspection would have revealed the problem. FAR 52.236-3 requires the contractor to acknowledge it has “taken steps reasonably necessary to ascertain the nature and location of the work” and investigated conditions including “the character, quality, and quantity of surface and subsurface materials or obstacles to be encountered insofar as this information is reasonably ascertainable from an inspection of the site.”2Acquisition.gov. 48 CFR 52.236-3 – Site Investigation and Conditions Affecting the Work A contractor who skipped the walk-through is in a weak position no matter what turned up.
The line that controls most disputes is patent versus latent. A patent condition is one a competent bidder exercising ordinary care would see during a standard site visit: a boulder in the excavation path, an obvious drainage problem. The GAO has described site inspection clauses as “warning bidders that site conditions could affect performance cost,” with bidders assuming “risks of increased performance cost caused by observable site conditions.”3U.S. Government Accountability Office. B-193045 – Edw. Kocharian and Company, Inc. If it was visible from the surface, you own it.
Latent conditions are hidden below grade or behind existing construction and cannot be detected without specialized testing. Failing to find a latent condition during a standard walk-through does not bar a later claim. Unless the bidding documents specifically tell you to verify subsurface measurements, you are entitled to take the drawings and specifications at face value. Constructive knowledge is the one caveat: if adjacent projects had already exposed similar rock or contamination, a reviewer may conclude a reasonable bidder should have anticipated the same conditions next door.
Owner-provided plans and specifications carry an implied warranty of accuracy. The Supreme Court held in United States v. Spearin that a contractor building to owner-prepared plans “will not be responsible for the consequences of defects in the plans and specifications,” and that this warranty “is not overcome by the general clauses requiring the contractor to examine the site, to check up the plans, and to assume responsibility for the work until completion and acceptance.”4Legal Information Institute. United States v. Spearin, 248 U.S. 132 A contractor who notices obviously defective specifications and says nothing, however, loses the warranty’s protection.
Notice: The Deadline That Kills Most Claims
Timing is where otherwise valid claims die. AIA A201-2017 requires the contractor to “promptly provide notice to the Owner and the Architect before conditions are disturbed and in no event later than 14 days after first observance of the conditions.”5American Institute of Architects. AIA Document A201-2017 General Conditions of the Contract for Construction FAR 52.236-2 uses “promptly” without specifying a day count, but the expectation is the same: notify the contracting officer in writing before you disturb the conditions.1Acquisition.gov. 48 CFR 52.236-2 – Differing Site Conditions Check your actual contract. Missing the window can waive your right to additional money or time even when the condition was genuinely unforeseeable.
Send notice through a method that creates a verifiable record. Certified mail with return receipt works. The project’s digital management platform works if it timestamps and tracks recipients. Verbal notice to an inspector may count as constructive notice in some circumstances, but written notice is always safer.
Most contracts also require specific information in the notice itself: the date of discovery, the precise location, a description of how the condition differs from the contract documents, and a preliminary estimate of the impact on cost and schedule. A vague notice gives the owner a procedural reason to deny the claim without ever reaching the merits.
Documenting the Condition
What you can prove on paper decides the claim. Start the day the condition appears.
Daily work logs are the foundation: date, weather, crew size, equipment on site, and a narrative of what was encountered and how it differs from what the contract documents indicated. Time-stamped photographs should include a measuring tool for scale and should show the obstruction or soil variance clearly. If a geotechnical report or boring log characterized the site differently, flag that document as the specific representation you relied on at bid time.
Keep cost records broken down by activity and time period. The measured mile method, which boards of contract appeals have accepted as more reliable than published industry estimates, compares productivity during the impacted period to productivity on similar work under normal conditions. That comparison only works if your records can actually isolate the affected activities.
Keep Working While the Claim Is Pending
Stopping work is one of the most expensive mistakes available. AIA A201-2017, Section 15.1.4.1, states that “pending final resolution of a Claim…the Contractor shall proceed diligently with performance of the Contract and the Owner shall continue to make payments in accordance with the Contract Documents.”6University of Wisconsin System. AIA A201-2017 General Conditions of the Contract for Construction Federal contracts carry the same expectation. Walking off or deliberately slowing down gives the owner grounds for default termination, which erases whatever leverage the claim had given you.
You also owe a duty to mitigate. Re-sequence work so unaffected areas stay productive. Rent smaller specialized equipment instead of letting a full crew sit idle. Costs that could have been avoided get stripped out of the equitable adjustment during review.
Filing the Formal Claim
After notice, the formal submission usually takes the shape of a Request for Equitable Adjustment or a proposed change order. It states the monetary increase you are seeking and the number of additional calendar days you need. On federal projects, the equitable adjustment proposal has to break down material costs by trade and supplier, labor costs by trade and hourly rate, and equipment costs tied to specific operations.7eCFR. 48 CFR 552.243-71 – Equitable Adjustments If the owner accepts, a signed change order modifies the original price and completion date. On federal work, if the contracting officer denies the claim, you can appeal to the agency board of contract appeals within 90 days or bring a direct action in the U.S. Court of Federal Claims within 12 months.8Office of the Law Revision Counsel. 41 USC 7104 – Contractor’s Right of Appeal From Decision by Contracting Officer
What You Can Recover
A successful claim produces an equitable adjustment to the contract price and schedule. Recoverable categories are broader than many contractors realize:
- Direct costs. Additional labor, materials, and equipment to overcome the condition, documented with the breakdown federal rules require.7eCFR. 48 CFR 552.243-71 – Equitable Adjustments
- Indirect costs. Extended general conditions, site supervision, temporary facilities, and other time-dependent costs that run longer because the project runs longer. Base these on actual costs, not estimates.
- Home office overhead. When the delay keeps you from taking on other work, unabsorbed home office overhead is recoverable. On federal contracts, the Eichleay formula is the standard method: a daily overhead rate (contract billings divided by total company billings, applied to home office overhead) multiplied by the number of owner-caused delay days.
- Profit. A reasonable markup on direct costs. Federal regulations cap negotiated profit at 10 percent unless entitlement to a higher rate can be shown.7eCFR. 48 CFR 552.243-71 – Equitable Adjustments
- Delay damages. If the owner fails to investigate or respond promptly after notice, you can recover the increased costs of extended performance, including delay-related damages.
Protecting Your Schedule
A differing site condition is an excusable delay because it is outside your control, but excusable does not mean automatic. The contract completion date only changes when the owner executes a written modification. An oral promise to “extend the schedule” is worthless when liquidated damages start accruing.
File a written time extension request with a critical path analysis showing how the condition extended the overall project duration. Only delays to activities on the critical path push the completion date; delays to activities with float do not. If the owner denies or ignores a properly supported request, file a written protest, keep working toward the original deadline, and preserve the time claim separately. Silence can be read as agreement with the denial.
If the Contract Disclaims or Omits the Clause
Some owners try to shift all site risk through broad “as is” language or an express waiver of differing site condition claims. Courts generally enforce these clauses when they are clear, specific, and unambiguous. A vague catch-all buried in boilerplate is more vulnerable than a specific provision that was separately negotiated. A disclaimer that contradicts a differing site conditions clause in the same contract usually gets read narrowly rather than allowed to swallow the DSC protection entirely.
Private contracts sometimes leave the DSC clause out altogether. Without it, there is no contractual right to an equitable adjustment, and recovery depends on common law theories:
- Misrepresentation. The owner made an erroneous representation of material fact, you reasonably relied on it, and the reliance caused financial harm. This is the most common path for something resembling a Type I claim.
- Breach of implied warranty. Under Spearin, the owner impliedly warrants that plans and specifications are accurate and suitable. Owner-provided design documents that led you into unforeseen conditions fit here.4Legal Information Institute. United States v. Spearin, 248 U.S. 132
- Failure to disclose superior knowledge. The owner knew about a costly condition, knew you did not, and the contract documents did not put you on notice to investigate. Silence under those conditions can be actionable, and this resembles a Type II claim.
- Mutual mistake. Both parties believed the site had certain characteristics, both were wrong, and the mistake goes to the essence of the contract. A successful claim can lead to contract reformation and quantum meruit recovery for the reasonable value of work performed.
Each theory carries a heavier burden than a standard equitable adjustment under a DSC clause. Proving intentional concealment, in particular, requires evidence that the owner knowingly hid a condition to drive bids down. If you are about to sign a contract without a differing site conditions clause, price that risk into the bid or negotiate for the clause before signing.