IICRC water Category 1/2/3 & Class 1-4
The IICRC S500 standard rates two things about a water loss: the Category (how contaminated the water is — 1 clean, 2 gray, 3 black) and the Class (how much water and how hard it is to dry — 1 to 4). Category drives the safety and demolition; Class drives the drying equipment. These are labeled reference definitions, not medical advice. Use them in the Category/Class helper.
| IICRC classification | Typical source / meaning | Handling / drying implication |
|---|---|---|
| Category 1 — clean water | Sanitary source: supply line, rain, melting snow | Degrades to Cat 2 in ~48–72 hr |
| Category 2 — gray water | Washing-machine/dishwasher overflow, sump failure | Contaminated — PPE, remove some porous materials |
| Category 3 — black water | Sewage, rising flood water, sea water | ⚠️ Health hazard — certified pros only, remove porous materials |
| Class 1 — least water | Small area, low porosity, minimal absorption | Fastest to dry |
| Class 2 — large area | Whole room with carpet + pad, water wicked <24 in | More air movers + dehumidification |
| Class 3 — greatest water | Water came from overhead, saturated ceilings/walls | Maximum drying capacity |
| Class 4 — specialty drying | Deep/bound water in hardwood, plaster, concrete | Special methods (heat, desiccant) |
Category rates how contaminated the water is; Class rates how much water and how hard it is to dry. Labeled reference definitions (IICRC S500) — not medical advice.
Category × Class: the full grid
| Class ↓ / Category → | Category 1 — clean water | Category 2 — gray water | Category 3 — black water |
|---|---|---|---|
| Class 1 — least water | Mop-up scale. Extract, a couple of air movers, dry in a day or two. The cheapest loss there is. | Small but contaminated: PPE, clean and sanitize, discard wet porous items. Drying itself stays quick. | Small footprint, still a health hazard. Porous materials are cut out and discarded, not dried. A small area is no reason to DIY it. |
| Class 2 — large area | The classic whole-room clean loss. Extract, then a full air-mover and LGR set. Dry fast — past ~48–72 hr it becomes Category 2. | Whole room, contaminated: carpet pad generally discarded, surfaces sanitized, full drying set on what stays. | Room-scale black water. Carpet, pad and lower drywall come out rather than dry — this is demolition with drying after, not a drying job. |
| Class 3 — greatest water | Water from overhead: saturated ceilings, insulation and walls. The heaviest clean-water drying load and the most equipment-days. | Overhead gray water. Saturated ceilings and insulation are removed rather than dried, with aggressive drying of the remaining structure. | Overhead black water — a sewer line or flood above. Extensive removal of porous assemblies under containment, certified crew only. |
| Class 4 — specialty / deep-bound water | Clean water bound into hardwood, plaster or concrete. Specialty drying — mats, panels, desiccants — and the longest timeline. | Bound water plus contamination. Specialty drying only where the material can be sanitized; otherwise it is removed. | Bound black water. Assemblies that absorbed it generally come out: specialty drying is rarely justifiable on contaminated bound water. |
Read down for the drying job and across for the safety job: Class sets how much equipment and how many days (size it in the drying equipment calculator), Category sets what has to be removed and who may handle it (it also multiplies the rate in the water damage restoration cost tool). Labeled reference definitions from IICRC S500 — not medical advice.