Cal. Civil Code § 936

Each and every provision of the other chapters of this title apply to general contractors, subcontractors, material suppliers, individual product manufacturers, and design professionals to the extent that the general contractors, subcontractors, material suppliers, individual product manufacturers, and design professionals caused, in whole or in part, a violation of a particular standard as the result of a negligent act or omission or a breach of contract. In addition to the affirmative defenses set forth in Section 945.5, a general contractor, subcontractor, material supplier, design professional, individual product manufacturer, or other entity may also offer common law and contractual defenses as applicable to any claimed violation of a standard. All actions by a claimant or builder to enforce an express contract, or any provision thereof, against a general contractor, subcontractor, material supplier, individual product manufacturer, or design professional is preserved. Nothing in this title modifies the law pertaining to joint and several liability for builders, general contractors, subcontractors, material suppliers, individual product manufacturer, and design professionals that contribute to any specific violation of this title. However, the negligence standard in this section does not apply to any general contractor, subcontractor, material supplier, individual product manufacturer, or design professional with respect to claims for which strict liability would apply.