Coinsurance Math and a Six-Day Shutdown
Ridgeline Fabrication LLC insures its Sumter machine shop on a commercial property form. The building's replacement cost is $1,200,000. The policy carries an $800,000 building limit, an 80% coinsurance clause, a $5,000 property deductible, and business income coverage with a 72-hour waiting period and a $200,000 limit. A spindle fire on July 8 damaged the building; the adjuster's accepted repair cost, at replacement cost, is $200,000. Production stopped for six calendar days, and the accountant documents $28,000 in lost net income and continuing expenses for that period. The insured's agent had recommended a $1,000,000 limit, which the owner declined in order to reduce premium.
1. Calculate the building payment. Show each step of the coinsurance calculation and explain what the result means to the insured.
Read the worked answer
Step 1: Required limit under the coinsurance clause 0.80 x $1,200,000 replacement cost = $960,000 required.
Step 2: Carry ratio (did insure / should have insured) $800,000 / $960,000 = 0.8333
Step 3: Apply the ratio to the loss $200,000 x 0.8333 = $166,666.67
Step 4: Apply the deductible $166,666.67 - $5,000 = $161,666.67 payable
The insured absorbs $38,333.33 of the loss beyond the deductible because it carried roughly 83% of the required limit. The penalty is not a punishment imposed after the fact; it is the mechanism that keeps the premium charged proportional to the exposure the insured chose to insure. Note that the loss ($200,000) is well under the policy limit, which is why the owner may believe the limit should not matter. Coinsurance applies to the relationship between the limit and the value, not to whether the loss exceeds the limit.
2. Calculate the business income payment and explain why the coinsurance penalty is calculated differently, if at all, for that coverage.
Read the worked answer
Lost income and continuing expenses: $28,000 over six calendar days = $4,666.67 per day.
Waiting period: 72 hours equals three calendar days. The waiting period operates as the time deductible for business income and is not reduced by partial days unless the form says otherwise.
Recoverable period: 6 days of loss minus 3 days waiting = 3 days.
Payment: 3 x $4,666.67 = $14,000 (well within the $200,000 limit).
Why coinsurance treatment differs:
- Business income is valued on actual loss sustained during the period of restoration, not on a scheduled property value, so many forms either omit coinsurance or apply it only if the insured elected a coinsurance percentage.
- Read the form: if a business income coinsurance or monthly limit endorsement applies, run the same did/should ratio against the annual projected income and the limit. Do not assume.
- Do not stack the $5,000 property deductible on top of the waiting period unless the form expressly applies the property deductible to business income. Double-deducting is a common and expensive error.
- If the period of restoration would have been shortened by reasonable extra expense, evaluate whether extra expense coverage produces a better result for the insured; the insured is entitled to the coverage that responds, not the one the adjuster finds convenient.
3. The owner insists the full $200,000 building loss must be paid because it is less than the $800,000 limit, and threatens to sue the agent. How do you respond?
Read the worked answer
Respond in writing, in plain language, with the math shown:
- Explain that the coinsurance clause compares the limit purchased to 80% of the replacement cost ($960,000), not to the size of the loss. Because $800,000 is less than $960,000, every loss is shared in the ratio 800/960.
- Point to the specific policy clause and the declarations page where the limit and coinsurance percentage appear, and to the replacement cost figure used, which should be documented by an appraisal or the adjuster's own estimate, not by the insured's assertion.
- Confirm whether an agreed value, reporting form, or inflation guard endorsement changes the calculation. If the policy was written on a reporting form with a premium adjustment, the penalty analysis is different and must be re-run.
- Offer the insured the option to submit a signed sworn statement of loss and to request a copy of the valuation documentation.
On the threatened suit against the agent: that is a separate dispute between the insured and the producer. The adjuster should not opine on the agent's conduct, should not admit or deny error and omissions exposure, and should document that the insured was told of the recommended higher limit. Pay only what the policy owes, and put the coinsurance explanation in the denial or payment letter so the record is clear if the file is later reviewed by the Department of Insurance or in litigation.