In construing a written contract, the controlling consideration is the intention of the parties as derived from all the terms of the contract. Legally, a written contract to which both parties have assented as a complete and accurate expression of their agreement, may not be varied or contradicted by understandings and negotiations, which occurred prior to signing the contract. Thus, as a general rule, a proposal by a contractor cannot be used to vary or contradict the signed contract.
Parol evidence
On the other hand, parol evidence will be admitted when a contract between parties is so ambiguous that its meaning is unclear. A contract is considered ambiguous "when it is reasonably susceptible to more than one meaning." As a result, if the contractor can show that the scope of work specified in the contract is ambiguous, then the contractor's proposal may be used to explain the meaning of the contract.
Public owners will likely argue that the scope of work specified in the contract is readily apparent and, therefore, the contractor should not be permitted to introduce its proposal as evidence on the issue of ambiguity. However, a court may conditionally consider extrinsic evidence, including the proposal, for the purpose of determining whether a contract is ambiguous. The courts would likely consider the public owner's interpretation of the scope of work and the contractor's proposal to determine if the signed contract is reasonably susceptible of two or more meanings. If the scope of the work described in the contract is ambiguous, then the contractor would likely be permitted to argue that its proposal is indicative of the parties' intent when they entered into the contract.
Cases involving ambiguous scope of work descriptions in specifications are abundant. For example, in a case involving a contract for the installation of communication systems, the United States Court of Claims held that the parol evidence rule was not a bar to the use of statements made by the parties during negotiations "in aid of the interpretation of ambiguous or uncertain clauses in written agreements." Sylvania Electric Products, Inc. v. United States, 458 F.2d 994, 1005 (Ct. Cl. 1972). The court also said that expressions of the parties made during negotiations for a contract are a "frequent source for interpretation" of the contract.
Disputes over scope of work questions frequently arise in subcontracts. In a case involving a federal construction contract, the prime contractor and a subcontractor agreed during negotiations that the subcontractor's bid would not include certain work, which was indicated in some of the contract documents but not in others. The trial court allowed the subcontractor to testify to the agreements reached during the negotiations. The Ninth Circuit Court of Appeals affirmed, and held that the parol evidence rule did not bar the use of extrinsic evidence in this case. The court stated that the rule "has no application where an ambiguity exists in connection with the requirements of the contract, its specifications and drawings. If a contract is obscure, or ambiguous in its terms, then its meaning is a question of fact and extrinsic evidence may be received in aid of its interpretation. Where a contract is ambiguous and where it has been interpreted by the parties themselves, then the contract should be enforced in accordance with such interpretation." United States v. F.D. Rich Co., Inc., 434 F.2d 855, 859 (9th Cir. 1970).
In a case involving a bridge painting contract in Missouri, the specifications were unclear as to the amount of sandblasting required to prepare for painting. The court recognized an established set of principles to be applied when the contract is found to be ambiguous, including determination of the intent of the parties.
Conclusions
In construing ambiguous contracts the objective is to ascertain and render effective the mutual intent of the parties; and to achieve this objective the court will consider the entire contract, subsidiary agreements, the relationship of the parties, the subject matter of the contract, the facts and circumstances surrounding the execution of the contract, the practical construction the parties themselves have placed on the contract by their acts and deeds, and other external circumstances, which cast light on the intent of the parties . . . so long as that evidence is not contradictory of, repugnant to, or inconsistent with the terms of the contract. Busch & Latta Painting Corp. v. State Highway Comm., 597 S.W.2d 189, 197-8 (Mo. Ct. App. 1980).
Clearly, the actual proposal of the contractor or subcontractor, as presented prior to the award of the contract and a ccepted by the other party, is a strong indication of the intent of the parties and would fall squarely into the list of acceptable evidence as cited above.