When Engineering Reports Cross the Line: Why Physical Findings Don't Determine Coverage

Your insurance company sends a forensic engineer to inspect your property after a loss. A few weeks later, you receive a denial letter that leans heavily on the engineer’s report. The engineer found a construction deficiency, an installation error, or a pre-existing condition somewhere in the chain of events — and the insurer has used that finding to deny the entire claim. The message, implicit or explicit, is that the engineer has determined your damage is “not covered.”

But here is the problem with that approach: engineers determine how something was built or how it failed. They do not determine whether it is covered.Coverage is a legal question governed by policy language, state law, and decades of judicial precedent. When an engineering report crosses the line from physical analysis into coverage conclusions, it is exceeding its scope — and the policyholder needs to understand why that distinction matters and how to challenge it.

The Role of Engineering Reports in Insurance Claims

Forensic engineering serves a legitimate and valuable purpose in insurance claims. Engineers examine physical conditions — structures, materials, systems — and determine how things were constructed, how they performed, and how they failed. A qualified forensic engineer can tell you whether a roof was installed according to manufacturer specifications, whether a foundation crack resulted from settlement or seismic activity, whether water intrusion originated from a flashing deficiency or a wind-driven rain event, or whether a fire started from electrical failure or an external source.

This is important work. Understanding the physical mechanism of failure is an essential part of investigating any property damage claim. Insurers hire forensic engineers to inspect damaged properties, and those inspections can provide valuable information about what happened physically to the structure.

The problem arises when engineering reports are used not as one input in a coverage determination, but as the sole basisfor denying a claim. When an insurer takes an engineer’s physical finding — “the flashing was not installed to code” or “the roof sheathing was not properly fastened” — and converts it directly into a coverage denial without any analysis of the applicable law, the engineering report has been transformed from a factual tool into a coverage denial tool. And that transformation raises serious questions about the insurer’s investigation and the engineer’s role.

Engineering Causation vs. Legal Causation

This is the central issue, and it is the distinction that most policyholders — and, frankly, many insurance adjusters — do not understand. There is a critical difference between engineering causation (what physically happened) and legal causation (what the policy covers based on the law).

An engineer can examine a water-damaged wall and identify every factor in the chain of events: the window flashing was not installed to the manufacturer’s specifications, the weather-resistive barrier behind the siding had a gap, and wind-driven rain during a storm penetrated the wall assembly through those deficiencies. The engineer has described the physical mechanism perfectly. But the engineer has not determined whether the damage is covered under the policy. That is a legal question.

Under California law, the “cause of loss” for coverage purposes is a legal determination, not an engineering determination. California follows the efficient proximate cause doctrine, which holds that when a loss results from a chain of events involving both covered and excluded perils, coverage depends on what the predominant or efficient proximatecause of the loss was. If the predominant cause is a covered peril, the claim is covered — even if an excluded or non-covered cause was part of the chain.

The key California authorities establishing this principle are well-settled:

• Sabella v. Wisler (1963) 59 Cal.2d 21: The seminal California Supreme Court case establishing the efficient proximate cause doctrine. The court held that when a covered peril sets in motion a chain of events leading to a loss, coverage exists even if an excluded peril was also involved, so long as the covered peril was the efficient proximate cause.
• Garvey v. State Farm Fire & Casualty Co. (1989) 48 Cal.3d 395: Reinforced and refined the efficient proximate cause doctrine. The California Supreme Court confirmed that the doctrine applies even when the policy contains an explicit exclusion for one of the concurring causes, as long as the predominant cause is a covered peril.
• California Insurance Code § 530:“An insurer is liable for a loss of which a peril insured against was the proximate cause, although a peril not contemplated by the contract may have been a remote cause of the loss; but he is not liable for a loss of which the peril insured against was only a remote cause.”
• CACI 2306 (Jury Instruction): The standard California jury instruction on efficient proximate cause, which instructs juries to determine the predominant cause of the loss and apply coverage accordingly.

All of these authorities say the same thing: you look at the predominant cause.An engineering report that identifies a construction deficiency as one factor in a chain of events has not answered the coverage question. The coverage question is which cause in that chain was predominant — and that is a legal determination, not an engineering one.

Why This Is California Law — and Why It Matters That Other States Differ

The efficient proximate cause doctrine described above is California law. It is not universal. Many states follow a fundamentally different approach — and the difference has enormous practical consequences for how engineering reports are used to deny claims.

Anti-Concurrent Causation Clauses: Enforceable Elsewhere, Void in California

Most modern insurance policies contain what is known as an anti-concurrent causation (ACC) clause. This language typically appears at the beginning of the exclusions section and reads something like:

“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 that contributes concurrently or in any sequence to the loss.”

In states that enforce ACC language, this clause means that if an excluded cause is anywherein the chain of events — even as a minor contributing factor — the entire claim can be denied. In those states, an engineering report that identifies a construction deficiency, soil settlement, wear and tear, or any other excluded cause as one contributing factor is effectively a kill shot: the ACC clause allows the insurer to deny the claim regardless of what the predominant cause was.

A handful of other states — including Washington, West Virginia, and North Dakota — have similarly refused to enforce ACC clauses. But in the majority of states, ACC language is enforceable, and the engineering-report-denial tactic carries far more weight. In those jurisdictions, the insurer does not need to prove that the construction deficiency was the predominant cause. It only needs to show that an excluded cause contributed “in any sequence” to the loss — a much lower bar.

This is why it matters that this article discusses California law specifically. If you are a policyholder or practitioner in a state that enforces ACC clauses, the legal framework for challenging an engineering-report-based denial is different, and the strategies that work in California may not apply in your jurisdiction. Consult with a qualified attorney in your state who understands your state’s position on concurrent causation.

For California policyholders, the takeaway is clear: your insurer cannot use anti-concurrent causation language to sidestep the efficient proximate cause analysis.An engineering report that identifies a contributing excluded cause does not end the inquiry. The question remains: what was the predominant cause? If it was a covered peril, the claim is covered — and the insurer’s remedy for the construction deficiency is subrogation against the responsible contractor, not denial of the policyholder’s claim.

How Engineering Findings Get Misused

The pattern is predictable and repeats on thousands of claims. Here is how it typically works:

1. A homeowner files a claim for water intrusion damage after a major rain event.
2. The insurer sends a forensic engineer to inspect the property.
3. The engineer examines the point of water entry and identifies a construction deficiency — perhaps the window flashing was not installed to the manufacturer’s specifications, or the roof-to-wall transition lacked a kick-out diverter.
4. The engineer’s report describes the physical findings and concludes (or strongly implies) that the water intrusion was caused by the “construction defect” or “installation deficiency.”
5. The insurer issues a denial letter citing the engineering report: the damage was caused by a construction defect, which is not a covered peril.

On its face, this may seem logical. But the analysis has a fatal flaw: a construction deficiency is the carrier’s subrogation target, not a coverage defense.

Think about what the insurer is really saying: “A contractor installed your flashing incorrectly, and wind-driven rain exploited that deficiency to enter your home. Because of the contractor’s error, we will not cover your water damage.” But the policyholder did not install the flashing. The policyholder bought a home, bought an insurance policy, and suffered water damage during a covered weather event. The efficient proximate cause of the loss is the wind-driven rain — a covered peril. The construction deficiency is a contributing factor that explains why the rain was able to penetrate, but it is not the predominant cause of the loss.

The insurer’s proper course of action is to pay the policyholder’s claim and then pursue the negligent contractor through subrogation. When the insurer instead uses the engineering finding to deny coverage, they are shifting the burden of the contractor’s negligence from the insurance company (which can pursue subrogation) to the policyholder (who may have no practical remedy against a contractor who is long gone, out of business, or judgment-proof).

The Proper Boundaries of Engineering Reports

A well-written engineering report stays within its lane. It reports physical observations and draws conclusions about physical mechanisms. A properly scoped engineering report should:

• Describe what was observed: The physical conditions of the structure, the damage, the materials, the installation details.
• Describe the mechanism of failure: How water entered, how the structural element failed, how the fire progressed — the physical chain of events.
• Identify contributing factors: Construction deficiencies, material defects, code violations, maintenance issues, weather conditions — all physical factors that contributed to the loss.
• Reference applicable standards: Building codes, manufacturer installation requirements, ASTM standards, engineering principles that inform the analysis.

What an engineering report should notdo is draw coverage conclusions. An engineer should not conclude that damage is “excluded,” “not covered,” “not the result of a covered peril,” or “attributable to a non-covered cause.” These are legal conclusions that require analysis of the policy language, applicable state law (including the efficient proximate cause doctrine), and judicial precedent — none of which are within the engineer’s professional competence.

When an engineering report drifts from physical findings into coverage language, it is worth asking a straightforward question: who does that framing actually serve? The policyholder benefits from accurate physical findings. The insurer benefits from physical findings framed as coverage conclusions. When an engineering report reads less like an objective physical analysis and more like a pre-written denial rationale, the report has crossed the line.

How to Challenge an Engineering Report Used to Deny Your Claim

If your claim has been denied based on an engineering report, you have multiple avenues to challenge both the report and the denial. Here is a systematic approach:

1. Request the Full, Unredacted Report

Many denial letters reference an engineering report but only include a summary or selected excerpts. You are entitled to the full report, including all photographs, appendices, and any correspondence between the engineer and the insurer. The full report often contains qualifications, caveats, and alternative explanations that the denial letter conveniently omits. Request the complete, unredacted report in writing, and note whether the insurer delays or resists providing it. See our guide on the insurer’s duty to investigate for more on what the insurer must disclose.

2. Examine the Engineer’s Relationship with the Insurer

Forensic engineering in the insurance context is a business relationship. Engineers who produce reports that insurers find useful get more assignments. Engineers who produce reports that support policyholder claims do not. This creates an inherent structural incentive that should inform how the report is evaluated. Check for:

• Repeat retention patterns: Does this engineering firm appear on denial after denial for this insurer? High-volume, exclusive relationships between specific engineering firms and specific insurers suggest that the firm’s business model depends on producing reports the insurer wants.
• Revenue concentration: In litigation, discovery may reveal what percentage of the firm’s revenue comes from a single insurer or a small group of insurers. Heavy revenue concentration creates financial dependence that can compromise objectivity.
• Template language: Compare the conclusions section of multiple reports from the same firm. If the conclusions use nearly identical language across different claims with different facts, the conclusions may be template-driven rather than fact-driven.

For a deeper discussion of bias in insurer-retained experts, see our guide on biased insurance experts.

3. Obtain Your Own Independent Engineering Evaluation

The single most effective response to an adverse engineering report is a competing engineering report from a genuinely independent engineer — one retained by you or your Public Adjuster, not one with a pre-existing relationship with the insurer. Your independent engineer should inspect the same conditions, review the same evidence, and provide their own professional opinion. When two qualified engineers reach different conclusions from the same physical evidence, the insurer can no longer claim that the engineering report settles the matter.

4. Compare Physical Findings with Conclusions

Read the engineering report carefully, distinguishing between what the engineer observed and what the engineer concluded. In many adverse engineering reports, the physical findings are accurate but the conclusions do not follow from those findings — or the conclusions leap from physical observations directly to coverage language without the intermediate analytical steps.

For example, an engineer might accurately observe that a roof flashing was not installed to the manufacturer’s specifications. That is a physical finding. But if the engineer then concludes that “the water intrusion was caused by a construction defect and not by the weather event,” that conclusion has made a causation determination that requires legal analysis the engineer is not qualified to perform. The flashing deficiency is a contributing factor; whether it is the “cause of loss” for coverage purposes is a legal question.

5. Review Whether All Potential Causes Were Addressed

A thorough engineering investigation considers all potential causes of the observed damage. An investigation that considers only the cause that supports a denial — while ignoring or dismissing other plausible causes that would support coverage — is not a thorough investigation. If the engineer’s report identifies a construction deficiency but does not address the role of the weather event, the wind speed data, the rain intensity, or the historical performance of the building before the weather event, the investigation is incomplete.

6. Invoke the Efficient Proximate Cause Doctrine

When the insurer cites an engineering report to deny a claim, the policyholder’s response should directly address the efficient proximate cause doctrine. Even accepting the engineer’s physical findings at face value, the legal question remains: what was the predominant cause of the loss? If a covered peril — wind, rain, hail, fire — was the predominant cause, the claim is covered under California law regardless of any contributing construction deficiency. The engineering report may explain why the covered peril was able to cause damage, but explaining the vulnerability does not change the predominant cause.

7. Evaluate the Adequacy of the Insurer’s Investigation

Finally, consider whether the insurer’s overall investigation was adequate. Under Jordan v. Allstate Ins. Co.(2007) 148 Cal.App.4th 1062, California insurers have a duty to conduct a thorough, fair, and objective investigation. Under 10 CCR § 2695, insurers must investigate claims in good faith and must not rely on biased or incomplete investigations to deny coverage. An investigation that consists entirely of hiring an engineer with a known tendency to attribute damage to non-covered causes, accepting that engineer’s conclusions without independent analysis, and converting those conclusions into a denial letter is not a thorough or fair investigation — it is an outcome-driven process dressed up as due diligence.

For more on the insurer’s investigative obligations, see our guides on the duty to investigate and bad faith insurance practices. For specific strategies on challenging carrier-retained engineers on roof claims, see our guide on defeating carrier engineer reports.

Conclusion

Forensic engineers do valuable work. They examine physical conditions, describe mechanisms of failure, and identify contributing factors. These are important capabilities, and the information they provide is a legitimate part of the claims investigation process.

But physical findings and legal coverage determinations are different disciplines. An engineer can tell you that a flashing was improperly installed. An engineer cannot tell you whether your water damage claim is covered under your insurance policy. That determination requires analysis of policy language, the efficient proximate cause doctrine, applicable case law, statutory provisions, and regulatory requirements — none of which fall within an engineer’s professional scope.

When an engineering report crosses the line from physical analysis into coverage conclusions, it is worth examining carefully. Ask whether the conclusions are supported by the findings. Ask whether all potential causes were considered. Ask whether the engineer’s business relationship with the insurer creates structural incentives. And ask the fundamental question: if the physical findings are accurate but the coverage question is a legal one, who benefits from an engineering report that frames physical findings as coverage answers?

The answer to that question tells you everything you need to know about why the report was written the way it was — and why you should not accept it as the final word on your claim.