Prevalence of Building Dampness

In 2009, 9.9% of U.S. homes had water damage from exterior leakage, while 8.1% had water damage from interior leakage based on data from the American Housing Survey of the U.S. Census. However, the survey did not cover dampness or mold. There is otherwise no national database on the prevalence of dampness and mold in U.S. houses; however, Table 1 compiles data from studies that reported prevalence of various moisture-related conditions in U.S. houses. There is considerable variation in the prevalence estimates for each of the indicated moisture categories. For the "any dampness or mold category", four of the studies report the prevalence to be 50% or more, while three report prevalence values below 50%. The largest study (Spengler, 1994) reports prevalence of dampness and mold in 50% of the homes. Excluding the Freeman study because it only included bathrooms, the population weighted average prevalence of dampness or mold from these studies is 47% in the U.S.

Table 1. Reported prevalence of dampness and mold in U.S. houses.

Author Location Population
(housing units)
Mold or mildew Water damage or dampness Basement water Any dampness or mold
Brunekreef 1989 [5] 6 U.S. cities 4625 30% 17% 32% 55%
Chiaverini 2003 [6] Rhode Island 2600   18%   23%
Freeman 2003 [7] New Jersey 4291 (Hispanic)       17% (in bathroom)
Hu 1997 [8] Los Angeles & San Diego 2041 8%      
Maier 1997 [9] Seattle 925 54% 20% 22% 68%
Slezak 1998 [10] Chicago 910 (Head Start)       16%
Spengler 1994 [11] 24 cities in U.S. & Canada 12,842 36% 24% 20% 50%
Stark 2003 [12] Boston 492 38% 34%   52%
Population weighted average     33% 22% 23% 47%*

* Population weighted average excludes Freeman (2003) because it only considered bathrooms

Much less data are available on the prevalence rates of dampness in other types of buildings. The largest identified data set for dampness in offices is from a survey by the U.S. Environmental Protection Agency of 100 representative public and commercial U.S. office buildings. Table 2 provides data on the prevalence of past water damage and current water leaks from this survey [13]. Eighty five percent of buildings had past water damage and 45% had current water leaks. For U.S. schools, a survey by the General Accounting Office reported that 30% of schools had plumbing problems and 27% had roof problems [14]; however, the nature of the problems were not described so the prevalence of associated dampness and mold cannot be determined. Many small studies have documented dampness problems in schools [15].

Table 2. Prevalence of past water damage and current water leaks from a survey of 100 representative U.S. office buildings [13].

Basement Roof Mechanical
Past Water Damage 85% 28% 50% 17% 71%
Current Leaks 45% 13% 15% 3% 34%