FAR 52.236-2—Differing Site Conditions.
Plain-English Summary
FAR 52.236-2, Differing Site Conditions, addresses how the parties handle unexpected physical conditions encountered at the work site and how those conditions can affect price and schedule. The clause covers two separate categories: (1) subsurface or latent physical conditions that differ materially from what the contract indicated, and (2) unknown physical conditions of an unusual nature that differ materially from conditions ordinarily encountered in similar work. It also sets out the contractor’s duty to give prompt written notice before disturbing the conditions, the contracting officer’s duty to investigate promptly, and the standard for an equitable adjustment when the differing conditions increase or decrease the cost or time required to perform the work. The clause further limits recovery by requiring timely notice, allowing the contracting officer to extend the notice period, and barring requests for adjustment after final payment. In practice, this clause is designed to reduce bidding uncertainty, encourage fair pricing, and allocate the risk of hidden or unusual site conditions in a way that protects both the government and the contractor when the actual site differs from what was reasonably expected.
Key Rules
Two types of differing conditions
The clause covers both materially different subsurface or latent conditions and unknown unusual physical conditions that differ from what is ordinarily encountered in similar work. The contractor must show the condition fits one of these categories and that it is materially different from what the contract indicated or what is normally expected.
Prompt written notice required
The contractor must give written notice to the contracting officer promptly and before the conditions are disturbed. This notice requirement is critical because it allows the government to inspect the condition while it is still in place and before the evidence is altered.
Government must investigate promptly
After receiving notice, the contracting officer must investigate the site conditions promptly. The investigation helps determine whether the condition is truly differing site conditions and whether it caused a cost or time impact.
Equitable adjustment available
If the conditions materially differ and cause an increase or decrease in the contractor’s cost or time to perform any part of the work, the contract must be equitably adjusted. The adjustment is made by written contract modification and can account for either added or reduced performance costs or time.
Notice is a condition to recovery
A contractor’s request for an equitable adjustment under this clause will not be allowed unless the required written notice was given. The contracting officer may extend the time for notice, but absent notice or an extension, the contractor generally loses the right to recover under the clause.
No claim after final payment
The contractor may not request an equitable adjustment for differing site conditions after final payment under the contract. This creates a hard cutoff and encourages timely identification and resolution of site-condition issues.
Responsibilities
Contractor
Inspect the site as required by the contract, promptly notify the contracting officer in writing before disturbing any suspected differing condition, preserve the condition for investigation when possible, document the impact on cost and schedule, and submit any request for equitable adjustment in a timely manner before final payment.
Contracting Officer
Receive and evaluate the contractor’s notice, investigate the site conditions promptly, determine whether the condition materially differs from what was indicated or ordinarily expected, decide whether to extend the notice period if appropriate, and issue a written contract modification for any equitable adjustment.
Agency
Administer the contract in a way that supports timely site investigation and fair resolution of differing site condition issues, including ensuring the contract includes the clause when prescribed and that claims are processed consistently with the clause’s notice and final-payment limitations.
Practical Implications
Contractors should treat any unexpected soil, rock, groundwater, buried utilities, contamination, or other hidden condition as a potential differing site condition and notify the CO immediately in writing.
Failure to give prompt notice before disturbing the condition is one of the most common reasons recovery is denied, even when the condition is genuinely unexpected.
The clause can work both ways: if the condition reduces cost or time, the contract may be adjusted downward as well as upward.
Good documentation matters: photos, daily reports, test results, survey data, and contemporaneous correspondence often determine whether the contractor can prove the condition and its impact.
Final payment is a hard stop, so unresolved differing site condition issues should be raised and preserved well before closeout.
Official Regulatory Text
As prescribed in 36.502 , insert the following clause: Differing Site Conditions (Apr 1984) (a) The Contractor shall promptly, and before the conditions are disturbed, give a written notice to the Contracting Officer of- (1) Subsurface or latent physical conditions at the site which differ materially from those indicated in this contract; or (2) Unknown physical conditions at the site, of an unusual nature, which differ materially from those ordinarily encountered and generally recognized as inhering in work of the character provided for in the contract. (b) The Contracting Officer shall investigate the site conditions promptly after receiving the notice. If the conditions do materially so differ and cause an increase or decrease in the Contractor’s cost of, or the time required for, performing any part of the work under this contract, whether or not changed as a result of the conditions, an equitable adjustment shall be made under this clause and the contract modified in writing accordingly. (c) No request by the Contractor for an equitable adjustment to the contract under this clause shall be allowed, unless the Contractor has given the written notice required; provided , that the time prescribed in paragraph (a) of this clause for giving written notice may be extended by the Contracting Officer. (d) No request by the Contractor for an equitable adjustment to the contract for differing site conditions shall be allowed if made after final payment under this contract. (End of clause)