Water Damage Categories and Classes

The categories and classes come from the IICRC S500 standard, which most restoration companies and insurers follow. Knowing them helps you understand why a crew removes carpet pad in one job and dries it in place in another.

This topic is part of our complete guide to water damage restoration. The articles for this topic are listed at the end of the page.

The three categories of water

• Category 1, clean water: a broken supply line, an overflowing sink with no contaminants. Most materials can be dried if work starts quickly.
• Category 2, gray water: water with some contamination, such as a dishwasher or washing machine discharge or a toilet overflow with urine only. Carpet pad is usually removed.
• Category 3, black water: sewage, rising floodwater from outside, or any water that has sat long enough to grow bacteria. Porous materials it touches are removed and everything else is disinfected.

Water gets worse with time and contact. Clean water that runs through a dirty crawl space or sits for two or three days is treated as Category 2 or 3.

The four classes of water damage

• Class 1: a small area, mostly low-porosity materials. Quick to dry.
• Class 2: a whole room, with water wicking up walls less than about two feet. The most common class.
• Class 3: water came from above, soaking ceilings, walls, insulation and floors.
• Class 4: specialty drying, where water has soaked into dense materials like hardwood, plaster, concrete or brick.

The class tells the crew how much drying equipment to bring and roughly how long the job will take.