Getting Classifications Right: Avoiding Costly Drying Mistakes

Effective restoration relies on more than the right equipment. It also requires correctly classifying the job.

For example, picture this: a pipe bursts and causes a large-scale water intrusion. The contractor classifies it as a Class 2 loss and begins work. However, days later, drying progress is slow. Both the client and contractor are frustrated. After reassessment, the project was actually a Class 4 job. As a result, the misclassification shorted the project 20% of the LGR dehumidification it needed.

This happens often. Furthermore, it impacts drying efficiency and client satisfaction. Restoration surveys show that restorers most often classify jobs as Class 2. Yet most project conditions actually support a Class 4 classification — according to the IICRC S500 Standard for water damage restoration.

Understanding Current IICRC Classifications

The ANSI/IICRC S500 (5th Edition, 2021) Standard for Professional Water Damage Restoration classifies water losses by expected evaporation load. It also considers how deeply building materials have absorbed moisture. There are four classes:

Class 1 involves minimal water absorption. Less than 5% of porous materials are affected.

Class 2 refers to significant water absorption. Between 5–40% of porous materials are affected.

Class 3 represents the highest level of absorption in porous materials. More than 40% of the area is affected.

In addition, each of the first three classes includes this phrase from the S500:

“…where materials described as low evaporation materials or assemblies have absorbed minimal moisture.”

These classes apply when restoration begins immediately after flooding. In those cases, low evaporation materials have not had time to deeply absorb moisture. Therefore, projects that meet this condition fall into Class 1, 2, or 3 based on the percentage of wet porous materials in the drying chamber.

Class 4, however, is defined differently. The S500 defines it as:

“…water intrusion that involves a significant amount of water absorption into low evaporation materials (e.g., plaster, wood, concrete, masonry) or low evaporation assemblies (e.g., multilayer wallboard, multilayer subfloors, gym floors, or other complex, built-up assemblies). Drying may require special methods, longer drying times, or substantial water vapor pressure differentials.”

When the 2015 edition of the S500 was released, the criteria for Classes 1, 2, and 3 changed. Moreover, the 2015 edition explicitly expanded Class 4 to include many everyday restoration projects. In addition, the Class 4 dehumidification factors increased to match Class 3. As a result, Class 4 jobs now require the greatest amount of starting dehumidification.

Unfortunately, many contractors have not adopted these changes. They continue to classify most jobs as Class 2 or even Class 1. Consequently, the result is inadequate dehumidification and slower drying progress.

How to Classify a Project as Class 4

To properly classify a project as Class 4, look for any of these indicators:

Ordinary Low Evaporation Materials: For instance, plaster, lumber, engineered wood, concrete, masonry, or wet exposed soil that has deeply absorbed water.

Multiple Layers: For example, assemblies being dried such as multilayer wallboard, double-layer subfloors, wood flooring assemblies, or gym floors.

Specialty Drying in Use: In other words, deeply held or trapped moisture in cavities or multi-layer assemblies that require specialized equipment or methods.

Class 4 Specialty Drying Equipment and Techniques

For multi-layer assemblies, warm dry air must reach past the outer layer to contact the inner layer. In some cases, it must also reach structural materials beyond. As a result, specialty equipment is essential.

Injection Drying of Multi-Layer Assemblies

Injection forces pressurized warm, dry air through ceiling, wall, and other voids. There are two main types:

• High pressure air injection uses slender tubes and ¼” diameter injectors, such as the Dri-Eaz® DriForce Air Drying System.
• Low pressure, high volume air injection typically uses an air mover with a snout attachment and larger diameter tubes or hoses.

Wood Floor Drying

In addition to injection drying, wood floor drying uses a mat-type negatively pressurized system, such as the Dri-Eaz DriForce® Rescue Mat System.

Special Drying Methods

Furthermore, a dedicated low grain refrigerant (LGR) or desiccant dehumidifier delivers warm dry air into a contained section of building materials through ducting. This creates aggressive drying conditions that target deeply absorbed moisture. Common names for this method include tenting, mini containment, plenum drying, and chambering.

All projects using these specialized methods are Class 4. As a result, using them on targeted areas is the most efficient way to create the water vapor pressure differentials that Class 4 requires.

Why Proper Classification Matters

1. Optimized Equipment Usage

The S500 offers calculations for recommended dehumidification capacity. For example, an 8,000 cubic foot drying chamber classified as Class 2 requires 160 pints per day (ppd). However, proper Class 4 classification increases this to 200 ppd — ensuring the most aggressive drying.

In addition, Class 4 requires the highest-performing dehumidification technologies: LGR and desiccant models. Standard dehumidifiers are not aggressive enough. Therefore, the S500 Factor Chart lists “N/A” for conventional refrigerant under Class 4.

2. Improved Drying Efficiency

Accurate classification leads to better efficiency. However, when a Class 4 job is misclassified as Class 2 or Class 1, the project gets far less dehumidification than it needs. As a result, drying slows down. Consequently, the contractor appears less efficient — even when the work is sound.

According to the IICRC, moreover, most everyday water restoration projects are Class 4. This includes projects with no specialty drying — as long as low evaporation materials like plywood have deeply absorbed moisture.mized Equipment Usag

3. Enhanced Revenue

Furthermore, Class 4 classification requires the highest level of dehumidification and the most effective drying technologies. On certain jobs, this can increase invoice totals and revenue for restoration contractors. When done accurately and professionally, clients benefit from better outcomes. At the same time, businesses achieve higher profitability.

The Path Forward

Overall, the IICRC S500 provides a classification framework that benefits both contractors and clients — when used correctly. Given how common Class 4 misclassification is, restoration professionals have a clear opportunity to improve their practices.

If a party disagrees with a Class 4 classification, focus the debate on the plain language in the S500 definitions. Do not let the argument shift away from the standard itself.

Ultimately, proper classification is not just about compliance. It is about delivering the best results, protecting property owners’ investments, and positioning your business as a trusted and efficient drying contractor. Equip your team with the knowledge to correctly identify Class 4 losses — and achieve better outcomes on every project.

Source: ANSI/IICRC S500 (5th Edition, 2021) Standard for Professional Water Damage Restoration, © 2021 Institute of Inspection Cleaning and Restoration Certification