The short answer
Water damage restoration is governed by ANSI/IICRC S500, which classifies losses by contamination category and by drying class. Category decides what is removed versus dried; class decides how hard the drying will be.
Water is the volume trade in restoration. It is also the one where the technical framework is most useful and most often mangled in public writing, usually by treating category and class as the same thing.
The operational reality is that category is not fixed at the moment of loss. Clean water degrades with time, temperature and contact with building materials. A loss reported on Friday and attended on Monday is frequently a different category from the one described on the phone, which is why documenting what you observed on arrival matters more than what was reported.
In this section
IICRC water categories, and why they set the price
Category 1, 2 and 3 explained, how category degrades with time, and why it is not the same as class.
How long water damage drying takes
Three to five days typically, longer for hardwood and plaster. What the dry standard actually means.
What is happening in this area
Drying duration is the largest single variable in a mitigation invoice, because equipment bills per unit per day. Files with a baseline reading, daily monitoring and a final reading against the dry standard are straightforward to defend; files without them are not.
Federal disaster declarations involving flood, hurricane, tropical storm and severe storm accounted for the large majority of restoration-relevant events we counted from 2015 to 2025. Water, in one form or another, is the trade.
This section summary is maintained rather than written once. It was last reviewed on 23 September 2026. If something here is out of date or wrong, tell us.