Information on Dampness and
Mold for Renters in California
Main points:
• Living in damp or moldy buildings increases the chances of
respiratory problems like asthma.
• The critical warning signs are visible mold, water damage,
damp materials, or mold smell.
• Dampness is needed for mold to grow, so if you control the
dampness, you control the mold.
• Dampness or mold indoors may make housing substandard,
per the California Health & Safety Code.
Beginning January 1, 2022, residential landlords shall provide this booklet to prospective
residential tenants prior to entering the rental or lease agreement, in accordance with the 2001
Toxic Mold Protection Act (HSC #26148). This booklet, which explains the potential health risks
and health impacts that may result from exposure to mold, was produced by the California
Department of Public Health (CDPH) in 2020, in both English and Spanish versions.
Health Problems from Damp or
Moldy Buildings
Signs of Dampness or Mold
Living or working in damp or moldy buildings
increases the risk of many harmful health problems,
including:
asthma attacks in people who already have
asthma
a new asthma diagnosis
respiratory infections, such as bronchitis
breathing symptoms, such as hay fever, sneezing,
stuffy nose, sore throat, wheezing, breathing
difficulty, or cough
eczema or skin rash
Mold can affect people differently. How much a
person is affected depends on how sensitive they are
and on how much they are exposed. Damp or moldy
buildings are linked to health problems in people
even if they do not have allergies.
Signs of dampness or mold that may cause health
problems include:
• visible mold (regardless of color), such as on walls
or ceilings, behind furniture or appliances, under
carpets, or even hidden in areas not seen in the
occupied areas of homes
• mold odor, noticed as an earthy, musty, or moldy
smell
• visible water damage, such as water-stains or
discoloration on walls or ceilings, peeling or
bubbled paint, warped floors, or rotting wood
• damp or moist materials, including condensation
on windows or walls
Any one of these signs indicates increased risks to
health, and the more that any of them are present,
the greater the risk of health problems. Tests that
identify the types of mold or the amounts of mold
in buildings are not useful in telling us about the
health risks. This is why CDPH does not recommend
testing for mold, such as measuring mold spores in
the air.
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Causes of Building Dampness that Can
Allow Mold to Grow
The dampness that is necessary for indoor mold to
grow can come from either inside or outside a
building.
Indoor sources include:
leaking or burst water pipes, for instance under
sinks inside walls
not enough venng to the outside by open
windows or exhaust fans in places where water is
used or moisture is produced (for example,
bathrooms, laundry areas, kitchens, and water
heaters)
condensaon (water droplets) on cold surfaces,
including windows
Outdoor sources include:
water coming in through leaky roofs or
poorly-sealed windows, or from ooding
damp, exposed dirt in crawl spaces
outdoor surfaces that slope and drain water
toward a building, including from a downspout
Fixing Dampness and Mold Problems
The California Health & Safety Code (HSC §17920.3) says that when dampness or visible mold (or
certain other condions) in a home is a hazard to the health of occupants, the home is
substandard and the property owner must x the condions. The Code excludes mold that is
“minor and found on surfaces that accumulate moisture as part of their properly funconing and
intended use.”
CDPH recommends xing dampness and mold problems as follows:
idenfying and correcng the source of any water that may allow mold to grow
rapid drying or removal of damp materials
cleaning or removing mold and moldy materials as rapidly and safely as possible
Note: if a moldy area is simply bleached, cleaned, or painted over—without fixing the source of
the dampness—the mold is likely to grow again.
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Renters in California
The California Health & Safety Code requires property owners to provide a rental unit that is safe and healthy
for the people living in it. Prospecve renters should look for obvious condions that show dampness or
mold, and also less obvious signs like water leaks under the kitchen and bathroom sinks or moldy odor in a
sealed-up home. Also look for condions likely to cause future problems, like a bathroom that has no
working vent fan or no window that opens, or a clothes dryer without an outside vent.
For renters who suspect there is dampness or mold:
1. Tell the property owner or manager. Early detecon and correcon of the dampness and mold
problems can reduce the risks to your health and prevent the problem from geng worse.
2. If your property owner will not respond to your concerns in a reasonable amount of me, contact your
local (city or county) code enforcement agency and ask for a code enforcement ocer to inspect for
violaons. Many dampness or mold problems in rental homes are the responsibility of the property
owner and must be addressed by them. However, a code enforcement ocer may determine that
dampness or mold in a building results from a tenant’s acons or inacons – for instance, not using
available bathroom venlaon during showers.
3. If the local inspector determines there is a violaon, they can require the property owner to correct the
problem.
Additional Resources
For general informaon on dampness and mold and a list of local code enforcement agencies, with a focus
on dampness and mold, see www.cdph.ca.gov/iaq/mold. To see an animated video series, Mold in the
Home, visit www.cdph.ca.gov/mold.
Property owners must provide a rental unit that is safe and healthy for the
people living in it.
Tenants must notify property owners of any dampness or mold problems.
For more information, visit CDPH website (www.cdph.ca.gov/Pages/contact_us.aspx)
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