Water classes describe how long the water may take to evaporate, based on how many surface areas are wet and how porous the affected materials are. This information is used to determine how much and what types of equipment are needed for the mitigation job.
1. Class 1
This class has the least amount of water absorption - less than 5% of area surfaces (floors, walls, and ceilings) are wet porous materials. Water evaporates slowly when less is present, so Class 1 has the slowest rate of evaporation.
This may involve materials that don't absorb a lot of water (ex. concrete) that is only lightly affected.
Examples:
- concrete basement floor that absorbed a small amount of water
- materials that are not very porous (plywood, structural lumber, concrete) that absorbed very little moisture
- wet carpet or padding has already been removed
2. Class 2
Evaporation will progress more quickly than Class 1. Porous materials are affected at more than 5% (but low-evaporation materials have only absorbed minimal moisture), and up to 40% of area surfaces are affected.
Examples:
- wet carpet, cushion, and water wicking up gypsum wallboard
- structure affected by Category 2 in which underlay was removed but other wet structural materials remain
- carpet and underlay are being dried in-place but no wicking up walls has occurred
3. Class 3
More water is present than with any other class, and so evaporation will progress fastest. More than 40% of area surfaces are wet porous materials.
Examples:
- water supply failure on second floor has saturated entire areas below with large amounts of water
- overhead water supply pipes malfunction
- carpet and underlay, walls, structure, and insulation are wet
4. Class 4
These are specialty drying situations. Wet materials may require a longer time to dry - water has saturated deeply and is held or trapped. Evaporation occurs slowly. Materials such as hardwood, plaster, brick, and others have significant absorption and need to be dried with desiccant and/or special methods of dehumidification with larger vapor pressure differentials.
Examples:
- plaster and lath walls are deeply saturated
- the affected structure has hardwood floors or very old construction with multiple layers
- loss in a gymnasium or on concrete or dirt floors
