Home Insurance Coinsurance Clause: Verify the Insured Amount
Check the minimum percentage required by the coinsurance clause and the reconstruction value used in the calculation.
Published 2026-07-21
The coinsurance clause sleeps in most home policies, and wakes at the moment of a partial loss — precisely the one most owners will experience. Its mechanism: the insured amount must reach a minimum percentage of the reconstruction value, often 80%; below that, the settlement of any partial loss shrinks in proportion to the shortfall, a $60,000 kitchen fire reimbursed incompletely, deductible on top. The penalty strikes the frequent losses, not just the total one, which makes underinsurance costly long before the catastrophe. Meeting the threshold gets verified through an up-to-date reconstruction appraisal, redone with the insurer's tool — years without adjustment and undeclared renovations widening the gap in silence. The dated appraisal is kept on file, evidence in any future disagreement. This article explains the penalty calculation with worked examples, the threshold check and the update that closes the gap.
Find the percentage the contract requires
A coinsurance clause requires insuring the building for at least a percentage of its rebuilding value, generally eighty, ninety or one hundred percent. That percentage appears in the policy's particular conditions, often in a discreet line, and it is not the same everywhere. Reading it is the first step because it sets the threshold below which any settlement will be reduced. A ninety percent policy on a building whose rebuilding costs four hundred thousand dollars therefore requires an insured amount of at least three hundred and sixty thousand.
Use the right rebuilding value
The clause is calculated on the rebuilding value on the day of the loss, not on the day the policy was taken out. That detail is what makes the clause dangerous: an insured amount perfectly adequate five years ago can find itself below the threshold today simply because construction costs have risen, with nothing about the building having changed. The valuation used must therefore be recent and reflect current material and labour costs in your region, two figures that have moved markedly in recent years.
Understand the proportional reduction
The penalty is not refusing the settlement but reducing it in proportion to the shortfall. A building insured for three hundred thousand dollars when the clause required three hundred and sixty thousand produces a ratio of eighty-three percent, applied to the settlement. A partial loss of fifty thousand dollars is then reimbursed at roughly forty-one thousand, less the deductible. That mechanism surprises people precisely because it strikes partial losses, which are the vast majority, while everyone pictures underinsurance as a problem reserved for total losses.
Keep a current valuation on file
Protection against this risk comes down to one practice: having a rebuilding cost valuation prepared, keeping it, and updating it every three or four years as well as after each major renovation. Many insurers provide that valuation at no charge and offer automatic indexing, which should be checked to confirm it genuinely tracks construction costs rather than a general price index. Some policies replace the clause with a replacement-cost guarantee carrying no coinsurance: that option, where it exists, eliminates the problem entirely and is worth asking for at renewal. Asking the question at renewal costs nothing, and the answer belongs in the file either way. Brokers field this question every renewal season and can produce the figure quickly.
Quebec scenario: compare before confirming
Rereading his policy before renewal, a teacher in Magog stumbles on an 80% coinsurance clause and realizes he has never understood it in fifteen years of contract. His broker translates it with an example that makes the mechanism unforgettable. The clause requires the insured amount to reach at least 80% of the reconstruction value; below that, the insurer may reduce the payout of any partial loss in proportion to the shortfall. His house needs $400,000 to rebuild: the threshold is $320,000. Yet his contract, never adjusted since purchase, shows $260,000. A $60,000 partial loss — a kitchen fire — would not pay $60,000: the settlement would be prorated, 260,000 over 320,000, about $48,750 minus the deductible — the penalty striking partial losses, by far the most frequent, not just total ones. The correction follows the diagnosis: an updated reconstruction appraisal, redone with the insurer's tool, establishes $405,000; the insured amount rises accordingly, the premium climbs $210 a year — the price of a contract that will pay what it promises. The dated appraisal goes into the file, useful evidence in any future disagreement, and one line joins the renewal ritual: verify that the contract's automatic indexing has kept pace with real costs, the coinsurance clause being unforgiving of forgotten years of inflation.
Checklist
- Find your policy's coinsurance clause
- Note the minimum required percentage
- Obtain an up-to-date reconstruction appraisal
- Compare the insured amount with the threshold
- Understand the pro-rata reduction of partial losses
- Adjust the insured amount without delay
- Accept the premium of a contract that will pay
- Keep the dated appraisal as evidence
- Verify the threshold at every renewal
Frequently asked questions
What exactly does a coinsurance clause do?
It requires the insured amount to reach a minimum percentage of the reconstruction value, often 80%. Below that, the settlement of any partial loss is reduced in proportion to the shortfall: a kitchen fire gets paid incompletely, deductible on top. The penalty strikes the frequent losses — not just the total one.
How do I know whether I meet the threshold?
Through an up-to-date reconstruction appraisal, redone with the insurer's tool: square footage, year, materials, outbuildings, finished basement. Compare the result with the contract's insured amount: years without adjustment, or undeclared renovations, widen the gap in silence.
What should be done with the appraisal once obtained?
Adjust the insured amount accordingly, accept the premium increase as the price of a contract that will pay what it promises, and keep the dated appraisal on file: it becomes your evidence in any future disagreement over meeting the threshold at the time of a loss.