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Mold Statistics (2026): 23 Facts About Mold in US Homes

Last updated July 10, 2026. Compiled by the Mold Scanner AI Editorial Team from federal, WHO, peer-reviewed, and insurance-industry sources.
Quick Answer

Studies compiled by Lawrence Berkeley National Laboratory put the average share of US homes with dampness or mold at about 47%. And a 2007 EPA-funded study estimated that roughly 21% of current US asthma cases are associated with damp, moldy homes. Below are 23 mold statistics for 2026, each linked to its primary source.

HUD American Housing Survey shares: dampness 21.0 percent, leaks 16.7 percent, musty odor 5.9 percent, visible mold 3.8 percent
What the HUD American Housing Survey finds in occupied US homes.
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47 percent of surveyed US homes show dampness or mold, per Lawrence Berkeley National Laboratory
47% of surveyed US homes show dampness or mold (LBNL).
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How common is mold in US homes?

Prevalence of dampness and mold
~47%
The population-weighted average prevalence of dampness or mold in US homes is about 47%, based on a synthesis of national studies. Four of those studies put it at 50% or more.
Source: Lawrence Berkeley National Laboratory, Prevalence of Building Dampness
3.77%
In the 2015 American Housing Survey, 3.77% of people in occupied US homes reported a large patch of mold inside, about 8.5 by 11 inches or bigger.
Source: HUD Cityscape, Vol. 23 No. 1 (2021)
2.76%
In the American Healthy Homes Survey II, trained technicians observed visible mold of any size in 2.76% of the housing units they inspected.
Source: HUD Cityscape, Vol. 23 No. 1 (2021)
5.85%
In the 2015 American Housing Survey, 5.85% of people reported frequent musty smells in their home. In the newer AHHS II, 13.4% self-reported frequent musty smells.
Source: HUD Cityscape, Vol. 23 No. 1 (2021)
16.7%
In the 2015 American Housing Survey, 16.7% of people in occupied homes reported an indoor or outdoor leak in the prior 12 months. Leaks feed the moisture that mold needs.
Source: HUD Cityscape, Vol. 23 No. 1 (2021)
21.0%
In the American Healthy Homes Survey II, 21.0% of people reported dampness in their home from broken pipes, ongoing leaks, heavy rain, or floods in the prior 12 months.
Source: HUD Cityscape, Vol. 23 No. 1 (2021)
10 to 50%
The World Health Organization estimates that indoor dampness affects 10 to 50% of indoor spaces across Europe, North America, Australia, India, and Japan.
Source: WHO Guidelines for Indoor Air Quality: Dampness and Mould (2009)
85%
In the studies compiled by Berkeley Lab, 85% of surveyed commercial office buildings had past water damage and 45% had a current leak. Mold is not just a home problem.
Source: Lawrence Berkeley National Laboratory, Prevalence of Building Dampness

Mold, asthma, and breathing

These are population-level study findings, not a diagnosis for any one home. If you have symptoms, talk to a physician.
~21%
A 2007 EPA-funded study by Mudarri and Fisk estimated that about 21% of current US asthma cases are associated with dampness and mold in the home, with a range of 12 to 29%.
Source: Mudarri & Fisk, Indoor Air (2007), PubMed
~4.6 million
The same 2007 study estimated that about 4.6 million US asthma cases could be attributable to dampness and mold at home, within a range of 2.7 to 6.3 million.
Source: Mudarri & Fisk (2007), full text via US DOE OSTI
30 to 50%
A 2007 review by Fisk and colleagues found that building dampness and mold were linked to roughly 30 to 50% increases in a range of respiratory and asthma-related outcomes.
Source: Fisk, Lei-Gomez & Mendell, Indoor Air (2007), PubMed

What mold costs the country

Economic estimates from peer-reviewed research
$15.1 billion
A 2016 study estimated the yearly US cost of asthma illness tied to home dampness and mold at $15.1 billion, in 2014 dollars, with a range of $9.4 to $20.6 billion.
Source: Mudarri, J. Environ. Public Health (2016), NIH PMC
$3.7 billion
The same 2016 study put the yearly US cost of allergic rhinitis tied to dampness and mold at $3.7 billion, plus $1.9 billion for acute bronchitis.
Source: Mudarri, J. Environ. Public Health (2016), NIH PMC

Mold and home insurance

Claim data from the Insurance Information Institute
Up to 28.7%
Water damage and freezing, which the III notes includes mold when it is covered, made up between 22.6% and 28.7% of homeowner insurance losses each year from 2019 to 2023.
Source: Insurance Information Institute
1 in 67
About 1 in 67 insured homes files a water damage or freezing claim in a given year, based on 2019 to 2023 data.
Source: Insurance Information Institute
$15,400
The average water damage and freezing claim was $15,400 over 2019 to 2023. Standard HO-3 home policies exclude most mold, and insurers often cap mold payouts near $1,000 to $10,000.
Source: Insurance Information Institute

Indoor air and how mold spreads

EPA and FEMA guidance
~90%
Americans spend about 90% of their time indoors, where the EPA says pollutant levels can run 2 to 5 times, and sometimes over 100 times, higher than outdoors.
Source: EPA, The Inside Story: A Guide to Indoor Air Quality
Below 60%
The EPA recommends keeping indoor relative humidity below 60%, and ideally between 30% and 50%, to hold back mold growth.
Source: EPA, A Brief Guide to Mold, Moisture, and Your Home
24 to 48 hours
If wet materials are dried within 24 to 48 hours of a leak, spill, or flood, the EPA says mold usually will not grow. FEMA gives the same window after flooding.
Source: EPA, Brief Guide to Mold and FEMA/CDC Mold Cleanup Guide
10 sq ft
The EPA says a mold patch under about 10 square feet can usually be cleaned by the homeowner with basic supplies and PPE. Bigger jobs may call for a professional.
Source: EPA, A Brief Guide to Mold, Moisture, and Your Home
2 to 5x
Indoor levels of some pollutants often run 2 to 5 times higher than outdoor levels, the EPA reports, and tighter, more energy-efficient homes can trap that moist air.
Source: EPA, The Inside Story: A Guide to Indoor Air Quality
Every home
Mold spores are present in every home and in outdoor air, per the EPA. There is no way to remove all mold indoors, so the real goal is controlling moisture.
Source: EPA, A Brief Guide to Mold, Moisture, and Your Home
Clean or dirty
FEMA and the EPA say the first flood cleanup step is checking whether the water is clean or contaminated. Clean water dried fast has the best odds of stopping mold.
Source: FEMA, Dealing With Mold & Mildew in Your Flood Damaged Home

What these numbers do and do not say

Prevalence numbers move around because surveys measure different things. A synthesis that counts any dampness or musty smell lands near 47%. A survey that counts only a large visible patch of mold lands near 3 to 4%. Both are correct. They just answer different questions.

The asthma and cost figures are population-level associations from research, not a verdict on your home or your health. They tell you mold and dampness matter at scale. They do not diagnose anyone. For symptoms, talk to a physician. For cleanup, follow EPA guidance on moisture control and PPE. If you want to see where mold hides, our guides on black mold and mycotoxin testing walk through the details.

Average homeowner insurance claim for mold and water damage is 15,400 dollars, per the Insurance Information Institute
Average mold and water damage claim (Insurance Information Institute).
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Frequently Asked Questions

How common is mold in US homes?

It depends on how you measure it. A synthesis of studies used by Berkeley Lab puts the average prevalence of dampness or mold in US homes near 47%. Surveys that count only a large visible patch report lower numbers. In the 2015 American Housing Survey, 3.77% of occupied homes reported a mold patch about 8.5 by 11 inches or bigger. You can spot many problems yourself with our free mold detection app.

What percentage of asthma is linked to mold?

A 2007 EPA-funded study by Mudarri and Fisk estimated that about 21% of current US asthma cases are associated with dampness and mold at home, with a range of 12 to 29%. That is an association across the whole population, not a diagnosis for any one home or person. If you have symptoms, talk to a physician.

How much does mold remediation cost?

It depends on the size of the job. The EPA says a mold patch under about 10 square feet can usually be cleaned by the homeowner with basic supplies and PPE, while larger jobs may need a professional. On insurance, standard HO-3 home policies exclude most mold, and insurers often cap mold payouts near $1,000 to $10,000.

How fast does mold grow after a flood?

Federal guidance from FEMA and the EPA says mold can start growing on damp materials within 24 to 48 hours. That is why the EPA recommends drying wet materials within that window. Warm, humid, poorly ventilated spaces speed it up.

Sources

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