A grading system was developed to rate the moisture damage profile of dwell
ings and to study the relationship between moisture-induced indoor air prob
lems and occupant health. A total of 630 randomly selected houses and apart
ments, built between 1950 and 1989, were visually inspected. Moisture obser
vations were standardized into three damage levels. Thus, a system to class
ify the homes into three grades was devised. The two grades of homes associ
ated with the highest levels of damage were graded as index homes.
Overall, 51% of the sample had some kind of moisture fault in them and one
in every three homes (33%) was classified as an index home. The mean number
of damage incidents in the index dwellings varied from 1.4 to 2.6. The mea
n number of damage incidents in the reference homes was 0.28. Prevalence of
index dwellings was significantly higher (p < 0.01) in houses (38%) than i
n apartments (26%). There was no major difference in the prevalence of inde
x buildings in houses built in any particular decade (30-35%). Moisture was
observed in 28% of bathrooms, in 10% of kitchens, and in 17% of other spac
es. Indoor relative humidity (RH) levels were low in most homes.