Commercial property insurance, valued to rebuild.

The coinsurance penalty is not a judgment call. It is a four-step calculation printed on the face of the form. The worked example in CP 00 10 10 12 uses a building worth $250,000, an 80% coinsurance requirement, a $100,000 limit and a $40,000 loss. The policy pays $19,750. The owner absorbs $20,250 on a $40,000 loss, because the building was insured to 50% of value instead of 80%. Source: ISO form CP 00 10 10 12, Building And Personal Property Coverage Form, F.1.

Why valuation matters more than premium

The single most dangerous number on the policy is the building limit. Insure to purchase price or market value instead of replacement cost and you are underinsured the day you sign, because the cost to rebuild has little to do with what you paid or what it would sell for. Underinsurance triggers a coinsurance penalty that reduces even a partial claim, so a stale valuation can cost far more than any premium you saved. The two mistakes behind most of it are worth understanding in detail: how the coinsurance penalty cuts a claim and replacement cost versus actual cash value.

What it does not cover on its own

A standard property form leaves real gaps an owner has to close deliberately: flood and earthquake are separate, code-upgrade costs need ordinance and law, mechanical and system failures need equipment breakdown, and an extended vacancy can suspend coverage. The policy is the floor of a program, not the whole program. For the full picture of what the form responds to and what it leaves out, see what commercial property insurance actually covers.

The form, and the condition that decides what you collect

On an ISO commercial property policy the building and its contents sit on CP 00 10 10 12, the Building And Personal Property Coverage Form. What perils it responds to is set by a separate causes-of-loss form, usually CP 10 30 09 17, the special form.

The provision that decides most disputes is F.1, the Coinsurance condition. It is a bargain: the carrier gives you a lower rate in exchange for your agreeing to insure the building to a stated percentage of its value, commonly 80%, 90% or 100%. Insure it for less and the form reduces every partial loss in proportion, whether or not the loss itself is anywhere near the limit.

The calculation is printed in the form, in four steps. Multiply the value of the property at the time of loss by the coinsurance percentage. Divide your limit by that figure. Multiply the loss, before the deductible, by that fraction. Subtract the deductible. There is no negotiation in it, and there is no way to see it coming from a declarations page alone, because the declarations show your limit and not the building's current value.

Two things get owners into it. The building appreciates and the limit does not. Or the limit was set from a purchase price or a tax assessment rather than from what it costs to rebuild. Those are different numbers and only one of them is what the form measures against.

There is a way out of the condition entirely. G.1 Agreed Value suspends coinsurance on the property it applies to, for the term shown, in exchange for a signed statement of values the carrier accepts. It has to be requested, and it has to be kept current. It is the single most useful thing to ask your agent about on an older building whose limit has not been revisited.

If code upgrades are part of your rebuild exposure, the giveback in this form is small and the real coverage is a separate endorsement. See ordinance and law coverage.

How we handle it

We confirm the building is valued to rebuild at today's costs, check the covered causes of loss and the deductibles, and identify the endorsements your building actually needs. Then we make sure the limit, the catastrophe response, and the lender requirements all line up before a loss tests them.