Anti-Concurrent Causation: The Insurance Clause That Denies Hurricane Wind Claims for Flood Reasons, and the 4 States That Refuse to Enforce It

The wind took the roof off at 3 a.m. The water came in two hours later. The carrier denied the entire claim, citing a single sentence buried on page 14 of the policy: "We do not insure for loss caused by any of the following events, regardless of any other cause or event contributing concurrently or in any sequence to the loss."

That sentence is the anti-concurrent causation clause. In four states it is unenforceable. In the other forty-six it is the most efficient denial mechanism the insurance industry has ever drafted. After Hurricane Helene, 53% of closed homeowner claims in North Carolina paid nothing. After Hurricane Milton in Florida, 39%. The pattern of those denials lines up almost exactly with where covered wind damage occurred concurrently with excluded flood damage. The clause is doing exactly what it was written to do.

If your claim was denied citing "concurrent causation" or your denial letter quotes the "regardless of" language, you are looking at the most consequential clause in modern homeowners insurance. Here is what it actually says, why it works the way it does, the four states that refuse to enforce it, and the moves that surface in litigation.

TL;DR

• The anti-concurrent causation (ACC) clause says that if a covered peril and an excluded peril combine to cause a loss, the entire loss is excluded. It overrides the standard "efficient proximate cause" rule that would have allocated coverage based on which peril dominated.
• The clause appears in nearly every ISO HO-3 form sold in the US since 1984, written into the "Exclusions" section, typically prefacing the listed exclusions with the phrase "regardless of any other cause or event contributing concurrently or in any sequence."
• Four states refuse to enforce ACC clauses by case law or statute: California, North Dakota, Washington, West Virginia. A handful of others limit enforcement at the margins.
• Carriers use ACC most aggressively in three contexts: wind + flood during hurricanes, earth movement + landslide + fire during wildfires and post-fire debris flows, and freeze + frozen pipe + flood of the kind the Texas 2021 freeze produced.
• Counter: demand a written allocation between covered and excluded perils, request the engineering report under your state's UCSPA, and check whether your state recognizes a "covered peril sufficient on its own" exception even where ACC is otherwise enforced.

The clause language

A typical ISO HO-3 ACC clause:

We do not insure for loss caused directly or indirectly by any of
the following. Such loss is excluded regardless of any other cause
or event contributing concurrently or in any sequence to the loss.
These exclusions apply whether or not the loss event results in
widespread damage or affects a substantial area.

[List of excluded perils follows: Ordinance or Law; Earth Movement;
Water Damage (including flood, surface water, storm surge); Power
Failure; Neglect; War; Nuclear Hazard; Intentional Loss;
Governmental Action.]

Two things this paragraph does that almost no homeowner notices at purchase:

1. "Regardless of any other cause" inverts the default rule. Historically, US insurance law applied the efficient proximate cause doctrine: when two perils combined, coverage was determined by which peril predominantly caused the loss. ACC overrides this entirely. If even a small portion of the loss is attributable to an excluded peril, the entire loss can be denied.

2. "In any sequence" eliminates the timing argument. It does not matter if the wind hit first and the flood second, or vice versa. Sequence-based arguments that worked under efficient proximate cause are foreclosed.

The clause was developed and pushed through state regulators starting in the 1980s in direct response to State Farm v. Partridge (CA 1973) and similar decisions that had expanded coverage under efficient proximate cause. The industry won the language fight in 46 states.

Where it bites: the wind-plus-flood pattern

The cleanest illustration: hurricane storm surge.

A typical homeowners policy covers wind. It excludes flood, including storm surge. When a hurricane hits, both perils arrive within hours of each other. Wind tears the roof off, surge floods the ground floor, and water from above and below saturates the entire structure. Without ACC, an adjuster would allocate: 60% wind, 40% flood, pay the wind portion. With ACC, the carrier denies everything.

Hurricane Helene (NC, September 2024) and Hurricane Milton (FL, October 2024) produced exactly this denial pattern at scale. Public claim-data audits by NC and FL regulators showed denial rates of 53% and 39% respectively. Many of those denials cite ACC. Litigation is now working through the trial courts in both states.

For the broader insurance policy red flags framework that ACC fits inside, see the pillar post.

The four-state carve-out

Four states refuse to enforce ACC clauses, either by court holding or statute:

California. Julian v. Hartford Underwriters Insurance Co. (Cal. 2005, not 2007 as sometimes cited) confirmed that California Insurance Code § 530 and § 532 codify the efficient proximate cause doctrine and that ACC clauses cannot override it. If a covered peril is the efficient proximate cause of loss, the loss is covered even if an excluded peril contributed. The rule extends to wildfire debris flows, freeze-then-pipe-burst patterns, and earthquake-then-fire patterns.

North Dakota. Western National Mutual Insurance v. University of North Dakota (ND 2002) held that ACC clauses violate the state's reasonable-expectations doctrine and statutory loss-causation rules.

Washington. McDonald v. State Farm Fire & Casualty Co. (Wash. 1991) and subsequent cases reject ACC as inconsistent with WA's efficient-proximate-cause statute. Recent cases extend the rule to wildfire-and-debris-flow combinations.

West Virginia. Murray v. State Farm (W. Va. 1998) and follow-on cases hold ACC clauses unconscionable as applied where they conflict with reasonable expectations. WV courts have applied this reasoning to flood + wind, freeze + pipe burst, and earth movement + fire.

A handful of other states limit ACC at the margins. New York courts have read ACC narrowly when the covered peril is "sufficient on its own" to cause the loss (the Pioneer Tower v. Insurance Corp. of New York line). Mississippi federal courts after Hurricane Katrina (Leonard v. Nationwide 2007) enforced ACC but only after detailed allocation, which gave plaintiffs leverage in subsequent settlements.

How ACC is invoked at claim time

If you live outside the 4-state carve-out and your claim involves any wind + flood, freeze + pipe, earth + fire, or similar combination, the carrier's adjuster will typically:

1. Retain a forensic engineer. The engineer's report attributes percentages to each peril. If any portion is attributed to an excluded peril, ACC kicks in.

2. Cite the policy ACC clause in the denial letter. State UCSPAs (Unfair Claim Settlement Practices Acts) require the specific clause to be quoted. Demand the quote in writing.

3. Refuse to allocate. Without ACC, allocation would be required. With ACC, the carrier argues no allocation is possible. The denial covers the entire loss.

The countermove that has worked in litigation:

Demand the engineering report. Most state UCSPAs require the carrier to provide the basis for the denial in writing. The engineer's allocation often understates the wind portion. Hire your own engineer for an independent review. Cost: $1,500-$5,000. Net recovery in catastrophe litigation often runs into six figures.

Argue covered-peril-sufficient-on-its-own. Even in ACC states, several jurisdictions recognize that if the covered peril alone would have caused the loss, the loss is covered regardless of any contributing excluded peril. NY, IA, and a growing list. Check your state.

File the DOI complaint. State Departments of Insurance can fine carriers for failure to quote the specific clause, failure to investigate, or failure to allocate. The DOI complaint paper trail is critical to any subsequent bad-faith litigation. See insurance claim denied for the full appeal framework.

The 2024-2025 wave

Hurricane Helene, Hurricane Milton, and the January 2025 Eaton fire / Palisades fire combined to produce the largest single concentration of ACC-denied claims in the post-Katrina era. Three patterns are now in litigation:

• Helene wind + flood in western NC, eastern TN, and northern GA. Trial-court rulings expected through 2026.
• Milton wind + storm surge along the FL Gulf Coast. FL OIR data shows higher denial rates in storm-surge zones than in wind-only zones, consistent with ACC.
• Eaton/Palisades fire + debris flow + earth movement in CA. CA's anti-ACC rule should preserve coverage; carriers are still attempting to deny on related "concurrent" grounds.

The CA Department of Insurance issued a January 2025 bulletin reminding carriers that ACC clauses are unenforceable against fire-then-debris-flow losses and that denials citing ACC will be referred for market-conduct exam. That bulletin is itself a citable authority on appeal.

What to do if your denial cites ACC

A clean checklist:

• Read the denial letter. Find the specific ACC language quoted.
• Identify your state. If CA, ND, WA, or WV, the ACC clause is unenforceable as a matter of law. Quote the controlling case in your appeal letter.
• If outside the carve-out, demand the engineer's report and the carrier's allocation analysis in writing.
• Hire an independent engineer for a competing report. The cost is small relative to the claim. The ACV vs replacement cost calculator lets you sanity-check the carrier's depreciation math on the wind-damaged portion, which is often where the allocation argument starts.
• File a DOI complaint citing the relevant UCSPA subsection on failure to investigate or failure to allocate.
• Consult a policyholder-side bad-faith attorney if the loss exceeds $50,000. Most work on contingency in catastrophe states.

The shape underneath ACC is the same as every other override clause in modern consumer contracts. The default rule, efficient proximate cause, was developed over a century to allocate fairly between insurer and insured. The ACC clause was drafted specifically to revert that default to the carrier's benefit, in language most homeowners cannot parse without a copy of Couch on Insurance. Reading it before purchase, before a storm, is the only window where the leverage shifts.

Redline reads insurance policies and denial letters in plain English. Photograph the denial letter, paste in the policy exclusions section, or upload the engineering report, and Redline flags the ACC language, your state's enforcement status, and the specific UCSPA hooks for appeal in seconds. One scan, one dollar. Available on iOS and Android.