MIAQC Publishes Recommendation for Dealing with Mold/Moisture Problems in Rental Properties

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This document was developed by the Maine Indoor Air Quality Council with input from landlord, tenant, public health, legal, and codes professionals to identify best practice processes to address moisture problems in rental properties.  It recommends specific actions and timelines to protect occupant health and minimize landlord property and financial loss. It affirms the shared responsibility of landlords and tenants to work collaboratively to identify and rectify mold and dampness problems in units.  

The recommendations provide guidance for both liquid water events (which are deemed to be emergency situations) and management of visible mold or mold odors.  Prompt, proper action during liquid water events can minimize the risk of property loss and occupant health problems due to mold growth.

Note:  The Maine Indoor Air Quality Council asks that you take a few minutes after reviewing this guidance to tell us what you think.  Do you have ideas for making the process better?  Would you be willing to use the guidance as part of a “pilot” study to determine its value?  Click here to take a brief survey.


  1. Mold is everywhere in our environment, both indoors and outdoors.  Problems arise when mold actively grows indoors.  Mold can damage a building and make building occupants sick.  

  2. Exposure to mold in indoor environments can impact the health of susceptible individuals:

Scientific studies of inhalation (breathing) mold exposures in the indoor environment have documented the following health effects: 

  • Simple irritant effects (itchy eyes, runny nose, headaches)
  • Allergies in susceptible individuals (It is not known in the general population how much exposure or for how long is required to cause allergy. 5-10% of the population may be mold allergic.)
  • Exacerbation of asthma (A link between mold and the development of asthma has not been established.)
  • Infections in individuals with suppressed immune systems (the molds that cause infection in healthy individuals are not typically found indoors.)

Serious health effects from inhalation exposure to mold in the indoor environment (e.g., toxic reactions, infectious diseases, and chronic irritation) have not been well characterized. Toxic effects of mold have only been demonstrated following experimental exposures in animal studies and studies involving ingestion (eating) of contaminated foods.

  • Mold needs moisture and a suitable substrate (food/host) in order to grow and survive. The primary means to minimize mold exposure is by controlling moisture. Moisture problems may occur in buildings as a result of water intrusion (water leakage through the roof, foundation, or walls), high relative humidity (causing condensation), internal plumbing leaks, or poor or inadequate housekeeping.
  • Mold growths, or colonies, can start to grow on a damp surface within 24 to 48 hours
  • To effectively address a mold problem in indoor environments, it is generally accepted practice to:
  1. Resolve the moisture problem causing the mold growth
    1. Remove moisture damaged material (following available best practice guidance)
    1. Properly clean the area (following available best practice guidance and applicable local regulations)

  2. Surface cleaning or application of agents to kill mold spores may not resolve the risk of health effect: mold does not have to be alive to cause allergic reaction.

  3. When repairing a moisture problem and doing mold clean up, it is extremely important to follow generally-accepted best practice principles for assessment, containment, waste disposal, and clean-up in order to protect the worker and prevent contaminating the rest of the building.  Guidance is available through the following resources, or hire the services of an educated, experienced professional.


Recommendations for How Landlords & Tenants Should Mutually
Address Mold & Moisture Problems in Rental Properties


Tenant’s Responsibilities for liquid water events:

  1. Notify* Landlord Immediately.

    Liquid water leaks are deemed to be emergency situations.  When liquid water is entering the unit in any location, the tenant should notify the landlord IMMEDIATELY. This notification should be considered as also giving the landlord permission to immediately access the unit. 

*Notification can be by phone, but written follow-up is recommended.

  • Allow Access.

    Tenant should allow access to landlord’s agents to repair/resolve any water leak in the building regardless of whether it’s their own unit or that of an adjacent unit, to remove wetted materials, and to clean/repair the area.

Tenant’s Responsibilities for Mold/Mold Odor Issues:

When a tenant discovers an area of active mold growth or a pervasive moldy odor in their unit, they should:

  1. Conduct a thorough self-inspection of the unit:
    1. Inspect the unit for moisture sources: wet clothing/laundry, rotten foods, unemptied trash, or uncleaned spills, pet waste, etc.

If mold growth or moldy odor is either unrelated to any of the above “housekeeping” related issues or cannot be identified, then the tenant should:

  • Notify Landlord.

As soon as possible, but no more than 5 business days, after identifying an area of mold growth or a moldy odor in their unit, the tenant should notify* their landlord when they know or suspect one of the following:

  1. Visible mold growth in the unit
    1. Noticeable mold odor in the unit

*Notification can be by phone, but written follow-up is recommended.

  • Allow Access.

    Tenants should grant their landlord or their agents/ access to the unit, after receiving reasonable notice*, for their investigation, repair, and clean-up of moisture sources and mold contamination. 

*state law specifies 24 hours written notice

  • Follow Recommendations.

Tenants should comply with all reasonable measures to eliminate the moisture source and remediate the impacted area (clean the area/mold/contamination.)


Landlord responsibilities for liquid water events:

  1. Liquid water events are deemed to be emergency situations.  Upon notification by tenant of the occurrence of a liquid water event in the unit, landlord should immediately investigate leak and do everything possible to stop the leaking, even if only temporarily.  (Some scenarios: turn off water to leaking pipe, clean off ice dam, patch up holes, cover with tarp, etc.)

  2. To prevent mold growth, remove all wetted materials within 12-24 hours. (see p. 11 in the EPA mold remediation guide for strategies for specific wetted materials). If material has been wet for more than 48 hours or if the timeline of wetness is unknown, the use of fans or other devices to “dry” materials is not recommended.

  3. Permanently repair the source of the water leak.

  4. Clean and repair affected areas.

Landlord Responsibilities for Mold Growth/Mold Odors:

  1. As soon as possible, but within 5 business days after notification by tenant, inspect the unit for evidence of mold growth and moldy odors, as well as presence of or evidence of chronic water leaks, moisture sources, etc.  Follow generally-accepted principles for determining when there is an issue that could damage property or impact human health.

  2. If necessary, within 5 business days of inspection/investigation of tenant complaint, develop a written evaluation and repair and remediation plan that follows generally accepted best practice principles for the repair and remediation of mold and moisture problems.  Share the plan with the tenant and seek their inclusion and cooperation in the process.
  • Assist tenants in finding alternative housing during clean up and repair if required to ensure the health and safety of the tenant.  Circumstances include but are not limited to:
    • Tenant is experiencing health effect from mold exposure or subsequent remediation work.
    • Remediation work scope requires significant demolition and repair which makes the living space not suitable for full habitation.

  • If the tenant continues to have documented health effect after repair and clean-up is complete,– allow them to break lease and move. The landlord shall not withhold return of the security deposit to the tenant solely because of the tenant’s need to break the lease due to the mold.

5.   Consider disclosing history of mold/moisture problems in the unit to prospective tenants, especially if those tenants have young children, asthma, chronic lung disease, or immune deficiency issues.

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