Homebuilding - Can one contractor sue a partner two years after a building mistake was discovered (and paid for by the one at fault)?

The answer to your question is "it depends." As a general matter, people who are in the legal relationship of general "partners" are jointly and severally liable for partnership debts. That means that each partner owes the other a duty to "contribute" (it is legally called the duty of contribution) to partnership debts and obligations. Where one partner has paid a debt to which the other partner has failed to contribute, the paying partner may sue the non-paying partner to compel contribution. In general, the statue of limitations for such suits is the period of time applicable to contract claims, which is rarely less than three years. There may be numerous defenses to the claim in your case. You should consult with an experienced commercial litigation attorney regarding such defenses. The foregoing is for information purposes only and is not to be deemed as legal advice.