Dampness and Mold in Buildings

mold damage wall with ladder

Dampness results from water incursion from internal sources such as leaking pipes or external sources like rainwater and flooding. It becomes a problem when materials in buildings (e.g., rugs, walls, ceiling tiles) become wet for extended periods of time. Excessive moisture in the air, such as high relative humidity, can also lead to excessive dampness.

Sources of water incursion are often readily apparent (e.g., leaks in the roof or windows or a burst pipe). Dampness is less obvious when affected materials and water sources are hidden. Examples include wet insulation in a ceiling or moisture in building foundation due to sloping of surrounding land.

Indoor dampness can cause or worsen health problems with building occupants because it can:

  • Cause the growth of bacteria and mold.
  • Attract insects such as cockroaches, rodents, and dust mites.
  • Cause release volatile organic compounds from wet building materials.


Dampness and Mold Assessment Tool for Schools and General Buildings

Photos of School and General-Purpose Buildings

The health of those who live, attend school, or work in damp buildings has been a growing concern for years. This is due to a broad range of reported building-related symptoms and illnesses. Research has found that people who spend time in damp buildings report health problems including the following:

  • Respiratory symptoms such as in nose, throat, lungs
  • Asthma developing or getting worse
  • Development or worsening of asthma
  • Hypersensitivity pneumonitis (a rare lung disease caused by an immune system response to breathing bacteria, fungi, organic dusts, and chemicals)
  • Respiratory infections
  • Allergic rhinitis (often called “hay fever”)
  • Bronchitis
  • Eczema

Exposures in damp buildings are complex. They vary from building to building and in different places within a building. Moisture allows indoor mold to multiply on building materials and surfaces. People inside buildings may be exposed to microbes and their structural components, such as spores and fungal fragments. Mold may produce substances that can cause or worsen health problems. These substances vary depending on the mold species and on conditions related to the indoor environment. Moisture can also attract cockroaches, rodents, and dust mites. Moisture-damaged building materials can release volatile organic compounds that can also cause health problems.

Researchers have not found exactly how much exposure to dampness-related substances it takes to cause health problems. Studies report that finding and correcting sources of dampness is more effective at preventing health problems than counting indoor microbes. NIOSH has developed a tool to help assess areas of dampness and prioritize remediation of problems areas in buildings.

School Buildings Form & Instructions
School Buildings (form only)

General Buildings Form & Instructions
General Buildings (form only)

NIOSH Alert: Preventing Occupational Respiratory Disease from Exposures Caused by Dampness in Office Buildings, Schools, and Other Nonindustrial Buildings

NIOSH requests assistance in preventing respiratory symptoms and disease from working in or occupying damp office buildings, schools, and other nonindustrial buildings. This Alert:

  • Describes the respiratory problems that occupants may experience from exposures in damp buildings.
  • Presents information on outbreaks of building-related respiratory disease.
  • Recommends ways to find, respond to, and prevent building dampness and related respiratory symptoms and disease.

NIOSH Alert: Preventing Occupational Respiratory Disease from Exposures Caused by Dampness in Office Buildings, Schools, and Other Nonindustrial Buildings
DHHS (NIOSH) Publication No. 2013-102 (November 2012)