Water Damage Classes (1-4)
The IICRC S500 standard's four-tier classification of how much water was absorbed and how hard it will be to dry, Class 1 (minimal absorption) through Class 4 (water trapped in low-permeance materials like hardwood, plaster, or masonry), distinct from [[concept-water-damage-categories|Category]], which measures contamination rather than drying difficulty.
Why it matters
Class determines the drying equipment and timeline a restoration job actually needs, a Class 4 loss requires specialized, longer-duration drying methods that a Class 1 loss never does, even when both involve the same amount of standing water initially.
On a real project
A small kitchen leak affecting only part of one room (Class 1) dries in a day or two with standard equipment, while the same volume of water soaking into a home's hardwood floors and plaster walls (Class 4) can take a week or more of specialized low-evaporation drying.
Who this matters most to
An Insurance Restoration Estimator uses the class, not just the category, to price the equipment count and drying timeline for a job, since class drives labor and equipment cost more directly than contamination level does.
Where this goes wrong
An estimator prices a water loss using a Class 2 drying timeline and equipment count, but the crew actually finds a Class 4 situation, water trapped in hardwood, plaster, and concrete requiring specialized low-evaporation drying. The under-scoped estimate leaves the restoration company absorbing the extra cost, or forces a disruptive supplement mid-job.