Legal Question in Construction Law in California

Re: Questionable

There are several cases on mistakes in contract bids that law students study, and probably lots of others, so the law is pretty well defined.

Generally, a bidder who has made a major mistake in a contract bid can withdraw the bid, notwithstanding that the owner has accepted the bid, if (a) the mistake was pretty obvious, so that the owner probably should have noticed it, or probably should have wondered why the bid was so low; (b) the contractor is prompt in admitting his mistake and asking to withdraw; and (c) the owner hasn't sustained any major harm in reliance upon the erroneous bid. It may also help the contractor's case if he wasn't highly negligent and his mistake was thus more or less forgivable.

Otherwise, courts are more likely to tell the bidder "tough luck, you made an offer, it was accepted, you're in contract."

The legal principle is called "unilateral mistake."

In your case, at least based on your side of the story, the contractor isn't likely to get much sympathy from a judge. However, this is a small-claims sized claim, and judges in Small Claims Court have a reputation for sometimes uneven and erroneous judgments. Good luck.