Breach of contract may be minor, or material.
A minor breach is substandard performance but one that does not cancel the contract.
A material breach goes to the "heart" of the matter wherein the performance is so bad, or nonexistent, that it validates the other party walking away from the contract.
Is it a minor or material breach? The Court would decide based on the following subjective factors:
1. The extent to which the injured party will be deprived of an expected benefit
2. The extent to which the party can be adequately compensated.
3. The extent to which the breaching party will suffer forfeiture.
4. The likelihood that the breaching party will cure their failure
5. The good faith of the breaching party.
For more on this, see HERE.
What someone in your situation wants to say that due to their missing the deadline without good reason, they may be liable for material breach of contract, and not only would someone in your situation find another contractor, but also, would hold them liable for the difference of the pay that was required to finish the job.
Of course, this is rather aggressive. Since one wants to maintain good relations, that threat is best saved for last.
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