Coinsurance: how an 80% clause can shrink a claim check

If your building’s limit is less than 80% of what it would cost to rebuild on the day of a loss, an 80% coinsurance clause cuts the claim in proportion, even when the damage is small. Insure a building that costs $2,000,000 to rebuild for $1,200,000, and a $200,000 fire pays $140,000 after a $10,000 deductible instead of $190,000.

The fix is a limit built on current replacement cost, or agreed value, an option that sets the clause aside for the policy year.

How does the coinsurance math work?

In effect, a coinsurance clause is a promise to insure the building to a set share of its value. Most commercial property policies enforce it with the same four steps. First, the insurer multiplies the building’s value at the time of the loss by the coinsurance percentage on your dec page. That’s your minimum. Then it divides your limit by the minimum, multiplies the loss by the result, and subtracts your deductible.

If your limit meets the minimum, the clause doesn’t reduce the claim. If it falls short, the claim is cut to the same fraction your limit is of the minimum.

Note the timing. The value in the first step is measured on the day of the loss, not the day you bought the policy. If the policy settles at replacement cost, the test uses what it costs to rebuild that day, and if it settles at actual cash value, the test uses rebuild cost minus depreciation.

A worked example: a $2,000,000 building and a $200,000 fire

Say you own a two-story mixed-use building with a restaurant downstairs and three offices above. A contractor puts the cost to rebuild it today at $2,000,000. You insured it for $1,200,000, roughly what you paid three years ago minus the land, and the policy carries 80% coinsurance and a $10,000 deductible. Then the kitchen catches fire. The damage to the first floor comes to $200,000.

1. Multiply the rebuild cost by the coinsurance percentage: $2,000,000 times 80% is $1,600,000, the least you needed to carry to avoid a penalty.
2. Divide your limit by that figure: $1,200,000 divided by $1,600,000 is 0.75.
3. Multiply the loss by the result: $200,000 times 0.75 is $150,000.
4. Subtract the deductible: $150,000 minus $10,000 is $140,000.

The damage came to one-sixth of your limit, and you still absorbed $60,000 of it: the $10,000 deductible plus a $50,000 penalty. With a limit of $1,600,000 or more, the same fire would have paid $190,000.

A total loss plays out differently. The formula works out to $1,490,000 on the full $2,000,000 loss, but the payment can’t exceed the limit, so you’d collect $1,200,000 with or without the clause. Coinsurance does its real damage on partial losses: the kitchen fire, the burst pipe, the section of roof that lets go in a storm. Those are exactly the losses owners who insure low on purpose expect to be safe from.

Why is market value the wrong number for your limit?

Market value is what a buyer would pay for the property, and it answers a different question. It includes the land, which doesn’t burn. It rises and falls with rents, interest rates, and the neighborhood, and none of that changes what it costs in labor and materials to put the same building back on the same lot.

They can be far apart. An older masonry building in a slow rental market might sell for $900,000 and cost $2,400,000 to rebuild, while a small building on an expensive corner lot can sell for twice its rebuild cost. Purchase price, the tax assessment, and the appraisal your lender ordered all measure the property as an investment, so none of them is a safe basis for a limit.

Replacement cost is what it would take to rebuild the same building with materials of like kind and quality at today’s prices. Your agent can estimate it from the square footage, construction type, number of stories, year built, and finishes, and an insurance appraisal goes further for large or unusual buildings. Update it when costs move. Say the rebuild cost of the building in the example rose from $2,000,000 to $2,300,000. The 80% line moved from $1,600,000 to $1,840,000, and a limit that cleared it at the last renewal may not clear it now.

Inflation guard, an option on many property forms, raises your limit by a set percentage over the policy year, which helps a sound limit keep pace but won’t rescue one that started too low.

Agreed value, and when to ask for it

Agreed value is an optional coverage on most commercial property forms that sets the coinsurance clause aside for the period shown on your dec page, usually the policy year. You sign a statement of values, the carrier accepts it, and a partial loss isn’t cut for underinsurance as long as your limit matches the agreed amount. If the limit is lower than the agreed value, the claim is cut in that proportion instead. When the period ends without being renewed, the coinsurance clause comes back on its own. Watch that date.

Ask for it in five situations. Many lenders require the coinsurance clause waived, and agreed value is the usual way to do it. Blanket policies that spread one limit across several buildings often come with agreed value or a high coinsurance percentage, and our page for real estate investors explains the margin clause that can come with a blanket. It also earns its place on older or unusual buildings whose rebuild cost is hard to pin down, after a renovation that changed the building, and in any year construction costs outran your limit.

Carriers usually want a current valuation before they agree, and the statement of values you sign becomes the number they hold you to for the year. Ask at renewal, when there’s time to get the valuation done.

One more place coinsurance hides: business income and rental value coverage often carries its own coinsurance percentage, measured against a year of income and expenses instead of rebuild cost. If you see a percentage next to that line on your dec page, it needs the same check with a different worksheet.

Check your own dec page in three steps

1. Find each building on your declarations or location schedule and note the limit, the coinsurance percentage, and whether it settles at replacement cost or actual cash value. If agreed value applies, the dec page shows it with an expiration date.
2. Get a current replacement cost figure for the building from a recent valuation, an insurance appraisal, or your agent, not the sale price, the tax value, or the loan appraisal.
3. Multiply that figure by the coinsurance percentage, then divide your limit by the result. Anything under 1.00 is the share of a partial loss you’d collect before the deductible if part of the building burned tomorrow.

Run the check for each building and each business personal property limit, since coinsurance applies to each item separately unless the policy uses a blanket limit.

If you’d rather not do the math alone, our free gap report reads your dec pages and schedule of values and flags any building whose limit sits under its coinsurance line. When you’re ready to fix a limit, a building quote starts from current values.