Legal Question in Construction Law in California

If the materials have actually been used and incorporated into your home, AND the material supplier complied with the preliminary requirements, then the material supplier may have a right to lien your home for the unpaid amount. That is the only circumstance in which you would be responsible for the payment, and even then the contractor would owe it to you, or you could deduct it if you have not already paid him in full.

You aren't responsible for making good the check per se. If the material supplier has complied with the 20-day preliminary notice requirement, it can ultimately oblige you to pay for the materials used on your project through enforcing its mechanic's lien, if necessary. The supplier should first deal with the contractor to make the check good, and only if it fails come after you to enforce a lien.