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Anti-concurrent causation clauses explained
One policy sentence can bar a whole loss if an excluded cause like flood played any part. How it works, which states limit it, and how to document a claim.
An anti-concurrent causation clause is wording in your policy saying that certain excluded causes, such as flood or earth movement, bar the loss "regardless of any other cause or event contributing concurrently or in any sequence." If an excluded cause is anywhere in the chain of events, the insurer can deny the claim even when a covered cause, like wind, also played a part. Some states limit that result by law or case law, and in others the clause is enforced as written, so the sequence of events and your state's rule often decide the outcome.
The language in the HO-3
Section I of the ISO HO 00 03 05 11 form lists the exclusions in two groups. The first group, Exclusion A, opens with this sentence: "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." That is the anti-concurrent causation (ACC) lead-in. It governs nine items:
- Ordinance or law
- Earth movement
- Water (flood, surface water, storm surge, sewer and sump backup, and water below the ground)
- Power failure off the premises
- Neglect
- War
- Nuclear hazard
- Intentional loss
- Governmental action
The second group, Exclusion B, covers weather conditions, acts or decisions of others, and faulty planning, workmanship, materials or maintenance. It lacks the ACC lead-in and says any ensuing loss not otherwise excluded is covered. A separate set of exclusions in the Perils Insured Against section, covering wear and tear, settling, rodents and the like, also works differently. So a policy can treat two causes in the same claim under different rules. Your insurer's form and any state amendatory endorsement control, so read the exact wording; see ISO homeowners forms and why your policy may differ.
Why the clause exists
Property policies cover many losses with several causes. Consider a hurricane: wind peels off shingles, rain enters, and later storm surge floods the first floor. Without a rule, each side could argue the cause that favors it. Courts have used different approaches, and the clause is the industry's attempt to settle the question by contract.
- Concurrent causation. If a covered cause is a concurrent cause of the loss, the loss is covered even when an excluded cause also contributed.
- Efficient proximate cause. The court looks for the predominant or moving cause. If that cause is covered, the loss is covered. If it is excluded, the loss is not.
- Enforcing the clause. If an excluded cause contributed at all, the loss is excluded.
An ACC clause pushes toward the third approach. Whether it succeeds depends on where you live and how the court reads the wording.
How courts in different states have handled it
These are decisions on particular policies. They illustrate the range, they are not a list of current law, and later cases may have changed things.
| State | What happened | Source |
|---|---|---|
| California | The efficient proximate cause rule rests on Insurance Code section 530. In Garvey v. State Farm (1989), the California Supreme Court held that coverage exists where the covered cause is the predominant cause; a concurrent covered cause alone does not create coverage. In Howell v. State Farm (1990), a fire that destroyed slope vegetation was held to be the efficient proximate cause of a later landslide, so the earth movement exclusion could not be applied. | California Department of Insurance notice, September 19, 2025 |
| Mississippi | After Hurricane Katrina, the Mississippi Supreme Court held in Corban v. USAA (2009) that the ACC clause in that policy did not apply to losses caused by wind, so wind damage that occurred before the flood remained covered. Storm surge itself stayed excluded. | Insurance Journal, October 9, 2009 |
| Florida | In Sebo v. American Home Assurance (December 1, 2016), the Florida Supreme Court applied the concurrent cause doctrine where independent perils combined and no single cause could be identified. It noted that the insurer had used anti-concurrent wording in other parts of its policy but not in the exclusion at issue. | Cozen O'Connor client alert, 2016 |
| Texas | In JAW The Pointe v. Lexington Insurance (April 24, 2015), the Texas Supreme Court enforced an ACC clause in an apartment complex's property policy where wind and flood combined to trigger city ordinance costs. | Thompson Coe summary |
Insurance Journal reported in 2013 that, in addition to California, North Dakota (by statute and court decision), West Virginia and Washington had limited ACC clauses in favor of the efficient proximate cause rule. Treat that as a lead to check, since it is dated.
California's insurance commissioner has made the point in current terms. A September 19, 2025 notice told insurers they may not deny flood, mudflow, mudslide or landslide claims if a wildfire, a covered peril, was the efficient proximate cause, and that once the insured shows basic coverage applies, the burden is on the insurer to prove an exclusion. The notice also cites Insurance Code section 530.5, enacted in 2018 after the Montecito mudslides. The earth movement side of that story is in the earth movement exclusion explained and landslides and mudflow: what's covered.
A worked example
Say a hurricane tears roof shingles off your Gulf Coast home at 2 a.m. and rain pours into the upstairs bedrooms (hypothetical). At 8 a.m., storm surge floods the first floor. Your policy has the standard ACC lead-in and no flood coverage.
How an insurer might analyze it: the upstairs rain damage came from wind, which is covered, and happened first. The first-floor damage came from surge, which is excluded under the water exclusion. A fair adjuster separates them. A less careful one points to the ACC clause and denies everything because flood "contributed in some sequence." The documentation you gather decides which version you face: time-stamped photos of the upstairs damage before the water arrived, a log of when the surge came, and a contractor or engineer's opinion on what each cause did. See wind vs water: the hurricane claim dispute and engineering reports and causation disputes.
The mirror case is harder. If the roof was already intact and surge alone caused the damage, there is nothing to separate, and the exclusion applies.
The case for and against the clause
Insurers argue that flood, earthquake and similar events are catastrophic, correlated losses that cannot be priced inside a standard homeowners premium, and that without clear language every such loss would be litigated for some covered contributor. Clear exclusions keep the premium lower for everyone and allow separate flood and earthquake policies to be priced properly.
Policyholders and regulators who disagree argue that most people do not read the lead-in, that it can wipe out coverage the buyer reasonably believed they had when a covered peril started the chain or did real separate damage, and that rules like efficient proximate cause protect reasonable expectations. Some states agree and some do not, which is why the same facts can come out differently in different places.
What to do
- Find the lead-in in your Section I exclusions and note which exclusions it covers. Ask your agent which state rule applies.
- Document the sequence from the first moment of damage. Photos with timestamps, weather data, repair invoices and notes on what you saw when matter more here than almost anywhere. See documenting damage: photos, video and receipts.
- Separate the damage by cause when you can, such as wind-driven rain versus rising water, and ask the adjuster to do the same in writing.
- Ask for the denial in writing, quoting the exclusion and the facts supporting it. If the letter relies on the ACC wording, ask which excluded cause the insurer says contributed and what evidence supports it.
- Get an independent opinion when causation is the dispute. A licensed engineer's report on the efficient or predominant cause can change the file.
- Escalate. homeowners claim denied: what to do next outlines the sequence, and how to file a complaint with your state insurance department covers state department complaints. When the question is a legal one about your state's rule, an attorney is the right resource.
Key takeaways
- The ISO HO-3 puts an anti-concurrent causation lead-in on nine exclusions, including water, earth movement and ordinance or law.
- The clause lets an insurer deny a whole loss if an excluded cause contributed "in any sequence," unless your state's law or courts limit that.
- California applies the efficient proximate cause rule under Insurance Code section 530. Courts in Mississippi and Florida found coverage in particular cases where the wording did not clearly bar it, and Texas enforced the clause in a commercial case.
- The order of events and your records often decide whether covered damage can be separated from excluded damage.
- Read your policy's exact wording and your state's rule before a storm, and document the sequence carefully after one.