Mold and the law

California disclosure requirements The California Association of Realtors provides a sales disclosure chart that explains what is and is not required as far as real estate transactions in the state.

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Uniform federal laws lacking, and state law remains on hold


Currently, there are no uniform federal laws that establish permissible levels of mold within a home or building. Nor are there uniform laws governing standards for mold removal. Such laws typically fall to the states. The federal Occupational Safety and Health Administration (OSHA) provides guidelines and standards for mold removal professionals (see Mold Remediation on our Articles page for more information).


As of January 2011, California law did not require disclosure of mold (see Cal. Health & Safety Code §§ 26140, 26141, 26147.) California’s Toxic Mold Protection Act requires that in most sales and lease transactions, sellers must disclose mold that either poses a health threat or exceeds permissible limits set by California’s Department of Health Services (CDHS). However, this disclosure doesn’t take effect until the CDHS establishes those mold exposure limits. The CDHS has not yet established such exposure limits. The Toxic Mold Protection Act does not require any disclosure in the interim period.

The California State Department of Toxic Substance Control provides an Environmental Hazards Handbook (PDF) to all buyers and sellers. The handbook includes a detailed chapter about mold.


The International Building Codes provide minimum requirements to ensure homeowner/occupant safety. These codes specify three areas related to mold prevention:

  • There must be proper ventilation of all interior habitable areas along with specific concealed spaces (International Building Code Section 1203)
  • The exterior envelope of all buildings must be provided with vapor retarders, water-resistive barriers and the necessary flashing (International Building Code Chapter 14)
  • The maintenance of existing buildings/structures is of the utmost importance. This includes the exterior of the structure as well as its plumbing and mechanical systems (International Property Maintenance Code, Sections 304, 403 and 504)