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Coinsurance is a provision found in many commercial property policies that ties the amount of coverage a policyholder carries to the amount they can ultimately collect on a claim, and it catches building owners off guard more often than almost any other policy mechanic. In simple terms, a coinsurance clause requires the policyholder to insure the property to at least a specified percentage of its value, commonly eighty, ninety, or one hundred percent, in exchange for full payment of a covered loss up to the policy limit. If the property is insured for less than that required percentage, the policy applies a penalty formula that reduces the claim payment proportionally, even if the loss itself is smaller than the policy limit.
The calculation generally compares the amount of insurance actually carried to the amount of insurance that should have been carried given the coinsurance percentage and the property’s value at the time of loss, and applies that ratio to the loss amount before any deductible is subtracted. This means a building that is significantly underinsured relative to its true replacement cost can see a claim payment reduced substantially, sometimes well beyond what the underinsurance itself might suggest at first glance, even for a partial loss affecting only a portion of the structure.
Because coinsurance calculations depend heavily on an accurate value for the insured property, questions about how that value was established, and whether it reflects current construction costs, often become part of the broader claim discussion. Construction costs for commercial buildings have shifted considerably in recent years due to material pricing and labor availability, and a building insured to a value set several years earlier may no longer reflect current replacement costs by the time a loss occurs. This is one reason many commercial policies now include or offer inflation guard endorsements, which automatically adjust the insured value over time.
A simplified illustration helps show why the mechanics matter. Suppose a building has a true replacement cost of one million dollars, the policy carries an eighty percent coinsurance requirement, and the owner insured the building for four hundred thousand dollars rather than the eight hundred thousand dollars that eighty percent coinsurance would call for. If a covered loss of one hundred thousand dollars occurs, the carrier divides the amount of insurance carried by the amount required, four hundred thousand over eight hundred thousand, and applies that fifty percent ratio to the loss before the deductible, resulting in a payment of fifty thousand dollars rather than the full one hundred thousand dollars of damage. This is why insurance-to-value accuracy matters well beyond simply avoiding a shortfall on a total loss.
An appraisal proceeding addresses the amount of loss, meaning the physical scope and cost of repairing or replacing damaged property, and does not apply or calculate coinsurance penalties, which are a policy administration matter handled between the carrier and the policyholder after the amount of loss has been established. Building owners who are uncertain whether their coverage limits align with current replacement costs are generally well served by reviewing that question with their insurance agent or broker independent of any specific claim.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.