Water Loss Class and Category
Plain-English categories 1, 2, 3 and classes 1 to 4.
Reference
Categories
- Category 1 Water from a sanitary source. Generally clean. Time and contact may shift to category 2 or 3.
- Category 2 Significantly contaminated water that could cause discomfort or sickness if consumed.
- Category 3 Grossly contaminated water. May contain pathogens, sewage, or harmful chemicals.
Classes
- Class 1 Least amount of water absorption and evaporation load: less than about 5% of the combined floor, wall and ceiling surface in the area is wet.
- Class 2 Significant water absorption and evaporation load: about 5 to 40% of the combined floor, wall and ceiling surface is wet.
- Class 3 Greatest water absorption and evaporation load: more than about 40% of the combined floor, wall and ceiling surface is wet.
- Class 4 Specialty drying situations. Materials with low porosity holding bound water (hardwood, plaster, masonry).
Checked against published worked examples from: IICRC S500-2021 water-damage category and class definitions.
Details, formula, and sources
Formula or table(reference page; no compute) IICRC S500-2021 water-loss classes (1 = least, 2 = significant, 3 = greatest absorption and evaporation load -- under 5% / 5-40% / over 40% of the floor, wall and ceiling surface wet -- and 4 = specialty drying of bound water in low-porosity materials) and categories (1 = sanitary / 2 = significantly contaminated / 3 = grossly contaminated). Original plain-English summary; standard text not reproduced.
Source and editionIICRC S500-2021 §10.6 (Class) and §10.5 (Category) by section.
Free accessIICRC S500-2021 licensed; original summaries free here. Industry overviews free at most restoration-equipment manufacturer (Phoenix, Dri-Eaz, B-Air) sites.
What governsEstimate. AHJ and licensed professional govern.