The Public Adjuster's Guide to Anti-Concurrent Causation

Note: This guide is based on standard ISO commercial property forms. Always verify specific policy editions and carrier-specific language.

Anti-concurrent causation (ACC) is a policy clause that bars coverage for an entire loss whenever an excluded peril contributes to it — regardless of how much damage the covered peril caused, and regardless of which peril struck first. It appears as "lead-in" language in the exclusions preamble of standard ISO Form CP 10 30 and many proprietary commercial property forms. For public adjusters, missing it at intake can collapse a claim that looked straightforward on site.

What Does the Anti-Concurrent Causation Clause Actually Say?

Standard ISO language (Form CP 10 30) places the ACC provision in the preamble to the exclusions section:

"We will not pay for loss or damage caused directly or indirectly by any of the following. Such loss or damage is excluded regardless of any other cause or event that contributes concurrently or in any sequence to the loss."

Plain-English translation: Once an excluded peril is anywhere in the causal chain — before, during, or after the covered peril — the exclusion applies to the entire loss. The covered damage doesn't get carved out. The entire claim is at risk.

Note the phrase "in any sequence." This is not limited to perils acting simultaneously. A covered peril that strikes days before an excluded peril can still trigger the clause.

Proprietary carrier forms present a separate trap. On ISO Form CP 10 30, the ACC language sits in the exclusions preamble where a careful reader will find it. On many proprietary forms, the equivalent language appears inside individual exclusion definitions — buried in the earth movement definition, for example, as "regardless of whether combined with water" — rather than as a lead-in to the exclusions section.

A review limited to the exclusions preamble will miss it entirely. Read every definition that modifies an excluded peril, not just the preamble.

Why "Mostly Covered" Isn't Enough: The Anti-Concurrent Causation Math Problem

A persistent misconception among newer adjusters is that demonstrating the covered peril caused most of the damage is sufficient to preserve the claim. Anti-concurrent causation eliminates that argument.

In Colo. Intergovernmental Risk Sharing Agency v. Northfield Ins. Co. (Colo. App. 2008), a jury determined that 90% of a roof collapse was caused by snow weight — a covered peril — with only 10% attributed to excluded causes. The court denied coverage for the entire loss because the policy contained ACC language. The percentage was irrelevant.

The practical implication: even a 1% contribution from an excluded peril is enough to trigger a total denial under ACC language in states that enforce the clause as written. This shifts the PA's task from damage allocation to damage segregation — a higher and fundamentally different evidentiary standard.

How Anti-Concurrent Causation Works in Practice: Two Claim Scenarios

Hurricane Wind + Storm Surge (Commercial Warehouse)

A Category 3 hurricane makes landfall along the Gulf Coast. Wind tears shingles from the roof of a commercial warehouse; storm surge drives four feet of water through the ground floor within hours. The PA documents everything, submits under an open-perils commercial policy, and expects at minimum the wind damage to be paid.

The carrier issues a full denial — not just for the flood — for everything, including the wind. The denial cites the ACC preamble. The carrier isn't disputing the physical evidence. It's pointing to the policy structure.

Burst Pipe → Foundation Movement (The Causal Chain Problem)

In Lawrence v. State Farm Fire & Cas. Co. (N.D. Iowa 2025), approximately 200,000 gallons of water from a burst pipe saturated the soil beneath a building's foundation, eventually causing foundation movement. The burst pipe was sudden and accidental — a covered peril. The intuitive expectation is that because the covered peril initiated the entire chain of events, coverage applies.

The court upheld a full denial. The earth movement exclusion carried ACC language and defined earth movement broadly to include settling and subsidence "regardless of whether combined with water." The clause reached backward through the causal chain, eliminating coverage for the pipe burst that started everything.

The same logic appeared in Dalmac Realty LLC v. Scottsdale Ins. Co. (D. Conn. 2025), where a burst pipe caused soil erosion and structural collapse. The court held that the ACC clause barred coverage for the entire loss, including damage directly attributable to the water release.

What this means at intake: When adjusting a water-damage loss, the relevant question is not just whether the water peril is covered. It's whether the water could have triggered any subsequent excluded peril — earth movement, collapse, or similar — and whether those exclusions carry ACC language.

Does Your State Enforce Anti-Concurrent Causation? Jurisdiction Matters

Enforceability of ACC clauses varies significantly by state, and jurisdiction is the first question a PA should answer when ACC language appears in the policy.

States with efficient proximate cause protections: Several states have adopted the efficient proximate cause doctrine, which holds that when multiple perils contribute to a loss, coverage is determined by the predominant or initiating cause. If that cause is covered, coverage follows — even if an excluded peril also contributed.

• Washington: In Key Tronic Corp. v. Aetna (CIGNA) Fire Underwriters Ins. Co. (Wash. 1994), the Washington Supreme Court held that the efficient proximate cause rule cannot be circumvented by exclusionary language.
• California: Courts have held that ACC exclusions are unenforceable to the extent they conflict with the efficient proximate cause doctrine codified in Insurance Code § 530.

States that enforce ACC as written:

• Texas has generally upheld ACC clauses as valid contractual provisions.
• Florida enforces ACC language but applies a burden-of-proof framework: once the insured demonstrates a covered loss occurred during the policy period, the burden shifts to the carrier to prove that an exclusion applies. This has meaningful strategic implications for how scope is presented (discussed below).

Most states fall somewhere between these poles. Jurisdiction determines strategy. That determination needs to happen before the first inspection report is written.

The Strategy That Survives: Segregation of Damages

Even in states that strictly enforce ACC clauses, one argument can survive: if the covered-peril damage and the excluded-peril damage are truly independent — two distinct loss events rather than one concurrent loss — the ACC preamble may not apply at all.

This is the segregation argument. The standard is demanding. It is not enough to show that damages can be divided between perils. The adjuster must demonstrate that the covered-peril damage stands alone as a distinct loss event that would have occurred regardless of whether the excluded peril followed.

On claims where stakes justify it, an independent engineering or forensic report drawing a bright line — physically and temporally — between the covered and excluded damage is often the difference between a viable segregation argument and one that doesn't survive scrutiny.

Florida procedural note: When a claim is presented with segregated, peril-specific scope and estimates in Florida, the carrier must disprove coverage on each line item rather than relying on a blanket ACC denial. Segregation doesn't eliminate the ACC argument, but it changes the practical dynamics of the dispute considerably.

How Anti-Concurrent Causation Denials Start at Intake

Many ACC failures don't begin with a denial letter. They begin in the first 48 hours.

If the initial claim submission, the first call with the carrier's adjuster, or the early documentation describes the loss as a single blended event involving multiple perils, that framing becomes very difficult to walk back. A statement as simple as "the building sustained wind and flood damage during the hurricane" can become the evidentiary foundation for an ACC denial. The carrier does not need to independently establish concurrent causation when the insured's own adjuster has already described it.

Anti-Concurrent Causation Intake Checklist

Run this before the first inspection report is written.

Anti-Concurrent Causation and Policy Analysis

Anti-concurrent causation is structural policy language. It doesn't appear in the coverage grant. It doesn't appear under the specific exclusion it modifies. It sits in the preamble — and a standard review focused on covered perils and exclusion lists will walk right past it.

The same problem applies to ACC-triggering definitions buried in the earth movement or water exclusion sections of proprietary forms. The language that determines whether a claim survives isn't always where adjusters are trained to look for it.

Frontera surfaces lead-in ACC language, identifies which exclusions it modifies, and flags ACC-triggering definitions in coverage analysis reports — with citations to the exact policy pages where the language appears. The goal is the same as this article: know what you're dealing with before the first inspection report is written, not after the denial letter arrives.

References

• Colo. Intergovernmental Risk Sharing Agency v. Northfield Ins. Co., 2008 WL 2837517 (Colo. App. 2008)
• Lawrence v. State Farm Fire & Cas. Co., No. 5:24-cv-04008 (N.D. Iowa 2025)
• Dalmac Realty LLC v. Scottsdale Ins. Co., No. 3:24-cv-00942 (D. Conn. 2025)
• Key Tronic Corp. v. Aetna (CIGNA) Fire Underwriters Ins. Co., 124 Wn.2d 618 (1994)
• Jones v. Federated Nat'l Ins. Co., 235 So. 3d 936 (Fla. 4th DCA 2018)

This article is for educational purposes and does not constitute legal advice. Consult coverage counsel on specific claims.