It's a Matter of Class

February 11, 2010
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The issue we’re looking at today is water “wicking” up walls and its impact on the Class of water loss as defined by “IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration.”

The scope and cost of a loss can increase significantly when there’s a change from, say, a Class 2 to a Class 3 or 4 loss, but first, a quick review of IICRC S500 standard language may be in order.

Classes of Water Loss

The term “Class of water” refers to the initial determination of the amount of water present and the likely or anticipated rate of evaporation. Determining the Class of water is an essential part of calculating the amount of initial dehumidification capacity necessary to handle the potential amount of water that evaporates within an affected area, and air movement for the drying process.

Classes provide an initial point of reference to aid in the type, size and amount of equipment initially installed on a water restoration project. However, situations can arise that require adjustments to the type, amount and size of equipment being used during drying. This information should be gathered during the moisture inspection of affected areas.

Classes of losses are designated as:
  • Class 1 (least amount of water, absorption and evaporation) – Water damage restoration projects that affect only part of a room or area; or larger areas containing materials that have absorbed minimal moisture. Little or no wet carpet and/or cushion are present.
  • Class 2 (large amount of water, absorption and evaporation) – Water damage restoration projects that affect at least an entire room of carpet and cushion (pad). Water has wicked up walls less than 24 inches. There is moisture remaining in structural materials (e.g., plywood, particle board, structural wood, VCT, concrete and substructure soil).
  • Class 3 (greatest amount of water, absorption and evaporation) – Restoration projects in which water has wicked up walls greater than 24 inches, or it enters from overhead affecting the ceiling, walls, insulation, carpet, cushion and subfloor. The entire area is saturated.
  • Class 4 (specialty drying situations) – These consist of wet materials with very low permeance/porosity (e.g., hardwood, plaster, brick, concrete, light weight concrete and stone). Typically, there are deep pockets of saturation, which require very low relative and specific humidity for drying.
You should also understand the difference between capillary action and wicking.

Capillary action is the movement of a liquid through a slender pathway. It is caused by adhesion, cohesion, and surface tension in liquids and their contact with the solid pathway.

Wicking is the upward migration of moisture or other liquids within fabrics (carpet, upholstery, draperies) or porous materials (drywall, wood), which spreads moisture and increases secondary damage. During drying, wicking brings moisture to the surface of materials so that it can be evaporated or vaporized into the air as humidity.

I recently received a picture (Image 1) that got me thinking about this subject. It clearly depicts a Class 3 water loss, as water has wicked upward almost to the drywall’s 4-foot mud line. Some visible mold in the picture indicates that the water loss has devolved into Condition 3 mold contamination (actual growth), possibly with Condition 2 contamination (settled spores) in adjacent areas.

I would suggest that the carpet and pad, if any, should have been removed immediately, which would render this a Class 2 loss. I suspect that it’s much better (and less expensive, from a restoration standpoint) to define this situation as a Class 3 loss rather than Condition 3 mold contamination, especially since mold is excluded from most homeowner’s policies these days.

Interestingly, the loss still may be defined as only Category 1 or 2 water, rather than Category 3, depending on pre-existing conditions, exposure time and ambient temperature. That conclusion is based on the definition of Category 3 water as that which “…is grossly contaminated and can contain pathogenic, toxigenic or other harmful agents…”

What most restorers seem to be missing is that the underlying decision criteria for determining the Class of loss is evaporation rate. Go back to the standard and look at the definitions of Classes of loss.

If I have a house with water-soaked carpet and pad, and with wicking up drywall less than 24 inches, S500 defines it as a Class 2 loss with a high rate of evaporation, and therefore the need for more initial dehumidification capacity.

If, however, I remove the carpet and pad, I might define the new situation I have created as a Class 1 or, unofficially speaking, a Class 1.5 loss.

If I have a Class 3 loss (overhead source with wet drywall, insulation, framing, carpet and pad), and I remove the carpet and pad along with the drywall (and especially if metal studs are present in a commercial building), then I may have created only a Class 2 loss (or perhaps the unofficial Class 1.5-), based on a lower evaporation rate.

Again, evaporation rate is what the Classes of water losses are all about.

To make things more complicated, however, even with (or without) the carpet, pad and drywall removed, which results in a very low rate of evaporation (Class 2 or even 1?), if a subfloor is concrete or double sheeted plywood and there are “deep pockets of saturation,” then arguably many situations might be defined as Class 4 losses, and it may be well to consider high-capacity desiccant dehumidification.

Frankly, I don’t recommend that you go there. Eventually, you’re going to have to use a little professional judgment, keeping in mind my previous ICS article on “Drying Concrete Slabs.” Trained, certified technicians on individual job sites usually are the best persons to make these judgment calls, but, if questioned, they should have good, logical reasons to back up their decisions.

Categories, Classes, Conditions: a little confusing at first but, with understanding, they become a very useful tool for professional water damage restorers.

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