IICRC S500 Equipment Calculator & Cheat Sheet

IICRC water classes describe how much water is present and how hard it is to remove—not “how bad the flood is” by itself. Use class with material type and drying strategy.

• Class 1

  Low porosity, minimal absorption. Water on low-evaporation materials (e.g., tile, sealed concrete, cabinet bases)—little has wicked into structure. Drying is usually faster with fewer specialty steps.

• Class 2

  Significant water in porous materials. Think carpet and pad, cushion under vinyl, or moisture in gypsum wallboard in the affected area—more evaporation load than Class 1.

• Class 3

  Greatest evaporation load. Water may have come from above or saturated multiple assemblies (e.g., wet insulation, ceilings, walls, and flooring together). Expect more equipment and longer monitoring.

• Class 4

  Deeply bound or low-permeance materials. Moisture trapped in hardwood, plaster, concrete, or crawlspaces often needs longer drying, specialty methods, or more aggressive dehumidification than typical Class 2–3 scenarios.