3. If the landscape architect now sues the owner for damages for breach of contract, which of the following concepts best supports the landscape architect's claim?

Normally, if a party's duty under a contract is conditional, there is no duty to perform unless the condition occurs. However, there are a number of situations where, even though the condition does not occur, the party must nonetheless perform the duty. In such situations, the condition or its non-occurrence is said to be «excused.»

A party who owes a conditional duty may indicate that he will not insist upon the occurrence of the condition before performing. In some circumstances, this willingness to forego the benefit of the condition will excuse the condition. When this occurs, the promisor is often said to have «waived» the condition.

If the party's willingness to forego the benefit of a condition occurs after the contract is formed, but before the condition fails to occur, consideration will usually be required to effectuate a valid waiver. If the condition was not a material part of the bargain, courts will usually find that a party's subsequent waiver of the condition was binding even without consideration. If the party's manifestation of waiver induces the other party to change his position in reliance on the waiver, the courts will also hold the waiver binding without consideration.

After a condition has failed to occur, the party whom the condition was intended to benefit may choose to ignore the non-occurrence and continue with their performance. Such a waiver after non-occurrence is not really a promise and therefore does not need consideration or detrimental reliance to be binding. In addition to expressly waiving a condition, a waiver will be implied by: (i) the continuation of performance by the person who would have benefitted from the condition; and (ii) the acceptance of benefits under the contract by that person.

Once a waiver has been given, it cannot be revoked if it was made after the time for the fulfillment of the condition has passed or if the other party has relied on the waiver.

Substantial performance is the standard used under common law to evaluate the performance of contracts. The parties performing the contract must meet the standard of substantial performance of the contract only, and performance does not have to be perfect. The standard of substantial performance is not met if there is a material breach by either of the parties. Substantial performance is not applicable where performance is subject to an express condition. The doctrine of substantial performance only applies to a constructive condition.

Promissory estoppel arises when a promise is made that the promisor should reasonably expect to induce action or forbearance on the part of the promise. When the promisee then relies on such a promise, a court may bind the promisor to the promise he made if injustice can only be avoided by the enforcement of the promise. The promissory estoppel doctrine requires actual reliance on the promise, and the reliance must have been foreseeable. Promissory estoppel is intended to stop the promisor from arguing that an underlying promise should not be legally upheld or enforced.

Recovery on a theory of unjust enrichment typically occurs where there was no contract between the parties, or a contract turns out to be invalid.

C is correct. Although the express condition to the owner-architect agreement never occurred (the necessary approval was not given), the owner waived the condition by ordering the work to proceed. Because the waiver occurred after the non-occurrence of the condition and the landscape architect relied on the waiver by completing 40% of the work, the owner may not revoke the waiver.

A is incorrect. This case involves an express, rather than a constructive condition, and subsequently, the doctrine of substantial performance does not apply.

B is incorrect. Promissory estoppel would not be the best theory to support the landscape architect given that it constitutes an alternative form of contract, and the architect can sue for breach of an actual contract.

D is incorrect. Unjust enrichment would not be the best theory for the landscape architect, because there was a valid contract here.