Somewhere in most contractors’ claim history is a storm file that came back reclassified. The invoice was built on a Category 3 scope, and the review came back saying the water was rain, not sewage. Or there’s the reverse – a reviewer treating a wind-driven rain loss as an automatic Category 3 event. Both approaches miss an important distinction in the standard, and it can come down, in part, to a single word.

The Five Words That Matter

The IICRC S500 defines the standard of care as practices common to reasonably prudent members of the trade who are recognized in the industry as qualified and competent. The Important Definitions section assigns the following terms a specific weight in relation to the standard of care, and the difference between them is the difference between an obligation and an option.

The S500 sorts its own instructions into two buckets: things that form part of the accepted standard of care, and things that don’t.

Important words inside the standard of care:

• Shall designates an obligation that is mandatory by natural law or regulatory requirement. It is not a judgment call.
• Should is also part of the standard of care, but it’s driven by professional practice rather than regulation. Departing from a should is permitted; departing without documenting it and telling the other parties is not.

Important words outside the standard of care, and what they mean:

• Recommended – advice.
• May – permission.
• Can – possibility. The standard is telling you something is achievable, not that it necessarily applies directly to your work.

Section 10.6.7 shows what that looks like inside one sentence. For Category 2 or 3 water intrusions, it says that remediation should occur prior to restorative drying, and restorers shall use contamination controls and appropriate worker protection. That shows two different levels of weight in the same sentence: the contamination controls and worker protection use mandatory language, while the drying sequence uses ‘should,’ meaning it is part of the accepted standard of care even though it’s not mandated by regulation.

The regulated-materials passage does the same thing. Where either a regulated or hazardous material or mold is part of a project, the standard says the presence of those substances does not directly determine or constitute a change in Category, it only says that qualified persons shall abate the regulated materials, or should remediate mold prior to drying.

A reviewer who reads that as ‘visible mold makes this Category 3’ has collapsed separate provisions of the standard into one, possibly incorrect, conclusion.

The ‘Weather Question’

The S500 Category 3 definition closes with a list of examples. The list ends with contaminated water that gets into the indoor environment, and it names wind-driven rain from hurricanes, tropical storms, and other weather events among the ways that can happen.

Read fast, that looks like a rule. It isn’t. The ANSI/IICRC S500 Consensus Body issued a formal position statement holding that top-down water ingress, wind-driven rain, and water from weather-related events are not automatically Category 3. The reasoning runs through two of the points in the example cited above.

First, the verb. The definition says examples of Category 3 water can include those things. Because “can” signifies an open possibility and is expressly not a component of the standard of care, the Consensus Body concluded it is not standard of care for all instances to be treated as Category 3.

Second, what the example points at. The text says, “contaminated water entering the structure,” but Category 3 is defined as “grossly contaminated”. In the Consensus Body’s framing, “grossly contaminated” water is the example, not wind-driven rain, and the example does not apply when the water is not “grossly contaminated”, regardless of how it entered the structure.

So, how does the call get made? Inspection and information gathering, then determination. The standard defines inspection as the process of gathering information needed to determine the category, condition, class, or status of a water intrusion, and defines the preliminary determination as the process performed by the restorer to establish the category of water for the purpose of establishing a scope of work. On the Consensus Body’s reading, the restorer’s preliminary determination should be based on the conditions identified through inspection and information gathering, including whether the water meets the S500 definition of gross contamination.

Why This Cuts Both Ways

The statement is usually read as a win for reviewers, and on a scope built from the weather alone it is. But it cuts the other way just as hard: a documented finding of gross contamination cannot be waved off because the water arrived as rain.

That’s what makes this a conversation rather than an argument, with both sides pointing at the same document to justify their conclusion. The document is arguably better than trading assertions about what storm water usually is, but it’s also an area where a precise definition is needed. For purposes of the S500 Category determination, what matters is the documented condition, not simply the peril.

The Practical Version

The standard does anticipate that some projects may require departure from its guidance. In the end, the contractor should know exactly what he’s defining and be prepared to back up his position if questioned. That means that prior to deviating from the standard of care, following a “shall” or a “should,” the restorer should document the circumstances that led to the decision, notify the materially interested parties, and document the communication before proceeding.

In the example given, the Consensus Body text is a position statement rather than standard text, specific to the fifth edition (2021), but it’s published on the IICRC’s website and it’s easy to send along with a rebuttal. When that invoice line item does come back reduced on standards grounds, two questions do most of the work: what does the standard actually say, and which verb does it use?

A shall is an obligation. A can is a possibility, and in the Category 3 list it’s what turns the weather language into an example rather than a rule. Knowing which one you are looking at, and having the inspection findings behind your determination, is much of what separates a defensible file from a questionable one.

In procedural terms, this provides a general outline that every contractor can use in terms of what should be documented on every water damage claim:

• where the water entered
• whether it contacted soil, floodwater, sewage, or other contaminants
• visible sediment, debris, oils, pesticides, or other contaminants
• affected materials and building areas
• elapsed time and environmental conditions
• photos supporting the observed conditions
• moisture and psychrometric readings
• the basis for the preliminary Category determination
• any subsequent facts that caused the Category determination to change

At One Claim Solution, our team reads these files every day, tying disputed line items back to the classification, documentation, and standards language supporting them. Our role is to help contractors turn that evidence into a clear, defensible claim.

For more practical interpretations of the IICRC S500 as it relates to water damage claims, see our recent post “Water Damage Categories and Classes: How Proper Classification Strengthens Your Invoice.”

Reference note: The S500 Category determination is a restoration and safety classification; it does not determine insurance coverage or the cause-of-loss determination under a policy. ANSI/IICRC S500-2021 is a copyrighted standard published by the Institute of Inspection, Cleaning and Restoration Certification and available for purchase at iicrc.org. Passages are summarized here in our own words for commentary and education; this post is not a substitute for the standard, and restorers relying on it should work from a current copy. Weather-related Category guidance is drawn from the ANSI/IICRC S500 Consensus Body Position Statement on Category of Water Damage and Weather-related Events (March 16, 2026), published by IICRC. IICRC® and S500 are marks of the Institute of Inspection, Cleaning and Restoration Certification. One Claim Solution is not affiliated with, endorsed by, or acting on behalf of IICRC.