Most Homes Are Underinsured. Here's the Ten-Minute Check on Yours.

Your premium went up again this year. Your coverage almost certainly did not keep pace with what it would actually cost to rebuild your house. Those two facts sit side by side on the same piece of paper, and most homeowners never notice, because the premium is the only number on a renewal notice that anyone reads.

The scale of this is not a rounding error. When researchers at the University of Colorado Boulder and the University of Wisconsin–Madison examined nearly 5,000 policyholders who filed claims after Colorado's 2021 Marshall Fire, they found 74% were underinsured. More than a third were severely underinsured, carrying limits below 75% of what their homes actually cost to replace. These were ordinary homeowners with ordinary policies who believed they were covered. The check can be done in ten minutes, and it is arithmetic, not argument.

Why market value, tax assessment, and rebuild cost are three different numbers

Start here, because almost every coverage gap traces back to confusing these three.

Market value is what a buyer would pay for your house today. It includes the land, the neighborhood, the school district, and whatever the local market is doing. Land does not burn. If your $800,000 house sits on a $300,000 lot, no insurance policy needs to cover that $300,000.

Tax assessed value is a municipal figure calculated for a municipal purpose. In many jurisdictions it is deliberately set at a fraction of market value and updated on a multi-year cycle. It has no relationship to construction cost.

Rebuild cost — also called replacement cost — is what a contractor would charge today to construct the same house on the lot you already own: materials, labor, permits, debris removal, architectural drawings, and the general contractor's overhead and profit. This is the only one of the three your dwelling coverage is sized against.

The gap runs both directions depending on where you live. In high-land-value markets, rebuild cost can be well below market value, and homeowners who insure to the sale price overpay for years. In older or inland housing stock, rebuild cost frequently exceeds market value — a 1940s house with plaster walls, oak floors, and a slate roof costs far more to reproduce than it sells for. Underinsurance clusters heavily in that second group.

Finding your Coverage A limit, and what it is actually promising

Pull your declarations page. It is the two-to-three-page summary that arrives with every renewal, and it is the only part of your policy you will ever reread. Near the top, under a heading like "Section I — Property Coverages," you will find a line labeled Coverage A — Dwelling followed by a dollar figure.

That number is the maximum your insurer will pay to rebuild the structure itself. Everything else on the page is sized off it. Coverage B (other structures — detached garage, fence, shed) is typically 10% of Coverage A. Coverage C (personal property) runs 50% to 70%. Coverage D (loss of use — the hotel and restaurant bills while you are displaced) is usually 20% to 30%. Raise or lower Coverage A and all three move with it.

So a dwelling limit that is 20% short does not just leave a 20% gap on the house. It quietly shrinks your contents coverage and your temporary living allowance by the same proportion, at the exact moment you need both.

Write your Coverage A figure down. You now need a second number to compare it against.

Estimating today's rebuild cost — three ways, ranked by what they cost you

The free version, ten minutes. Take your home's above-grade finished square footage — from the appraisal in your closing file, not from a listing site, which often counts space differently — and multiply it by a current local rebuild cost per square foot. Your regional homebuilders association publishes ranges, and a local general contractor will usually give you a number over the phone. Expect a wide range depending on finish level. This method is crude and it is still dramatically better than nothing, because it will tell you within a few minutes whether you are short by 5% or by 40%.

The agent's estimator, free, one phone call. Every insurer runs a replacement cost estimator. Call your agent and ask them to re-run yours, then ask for the input sheet. This is the step almost nobody takes, and it is where the real problem usually surfaces. The estimator is only as good as the data fed into it — and that data was frequently entered once, at the time the policy was written, from a public records lookup. Read every field: square footage, number of bathrooms, roof material, foundation type, exterior finish, interior grade. Correct what is wrong.

A professional replacement cost appraisal, several hundred dollars. An independent appraiser walks the house and produces a line-item construction estimate. Worth it for older homes, custom construction, unusual materials, or anything where the square-foot method obviously will not capture the build quality.

Compare the result to your Coverage A limit. If Coverage A is less than your rebuild estimate, you have found your gap.

The 80% rule: how a shortfall cuts your payment on a small claim, not just a total loss

Here is the part most homeowners do not know, and it is the single most important paragraph on this page.

You do not have to lose the whole house for underinsurance to cost you money. Most replacement cost policies contain a coinsurance provision requiring you to carry dwelling coverage of at least 80% of full replacement cost. Fall below that threshold and the insurer is entitled to reduce payment on every claim, proportionally — including a kitchen fire, a burst pipe, or a tree through the roof.

The math is straightforward. Payment equals your actual coverage divided by the coverage you should have carried, multiplied by the loss, minus your deductible.

Say your home's replacement cost is $500,000. The 80% threshold is $400,000. You carry $320,000 — a limit that felt generous when it was set in 2019 and has not moved much since. A fire does $80,000 of damage to one wing of the house. Your loss is well inside your limit, so you expect $80,000 less deductible. Instead: $320,000 ÷ $400,000 = 0.80, and 0.80 × $80,000 = $64,000, before the deductible comes out. Sixteen thousand dollars, on a claim nowhere near your policy limit, because of a threshold you never knew applied.

This is not a carrier playing games. The provision is printed in the policy, it exists to keep pricing fair across a book of business where everyone pays into the same pool, and it is enforced by arithmetic rather than by anyone's judgment. But it is buried in a document nobody reads, and that is a real information gap — one that costs homeowners money for entirely avoidable reasons.

Extended and guaranteed replacement cost, inflation guard, and what each one adds

Three endorsements exist specifically to close this gap. They are inexpensive relative to what they do.

Inflation guard raises your Coverage A limit automatically each year by a set percentage or an index tied to construction costs. It prevents slow drift. It does not fix a limit that was wrong when it was set — it escalates the error along with everything else.

Extended replacement cost adds a cushion above your Coverage A limit, typically 10% to 50%, with 25% being the most common. If you carry $500,000 with a 25% extension, you have $625,000 available to rebuild. This is the workhorse endorsement, and it is the one most worth asking about, because it is designed for exactly the scenario that breaks budgets: a regional disaster that spikes local labor and material prices at the moment everyone in your county needs a contractor at once.

Guaranteed replacement cost pays whatever it costs to rebuild, with no ceiling. It is the strongest protection available, it is not offered everywhere or on every home, and where it is available it generally requires you to insure to full estimated replacement cost and keep the home's data current. That last condition is the catch worth knowing about — the guarantee is conditional on the accuracy of what your insurer has on file.

Separately, check for an ordinance or law endorsement. Standard policies rebuild what you had, not what current code requires. On a house built before modern electrical, egress, and energy codes, bringing the rebuild up to code can add a substantial sum that the base policy will not touch.

The improvements that raise your rebuild cost and never reach the policy

Rebuild estimates go stale in two ways. Construction costs rise — which inflation guard partly handles — and the house itself changes, which nothing handles automatically.

Anything on this list raises what it would cost to reconstruct your home, and your insurer does not learn about it unless you say so:

• Finished basements and finished attics — often the largest single omission, because public records may still list the original square footage
• Additions, dormers, enclosed porches, three-season rooms
• Kitchen and bathroom renovations, particularly upgrades in cabinetry, counters, tile, and fixtures
• Roof replacement, especially a change in material
• Hardwood, stone, or custom millwork replacing builder-grade finishes
• New HVAC systems, generators, solar, and electrical service upgrades
• Detached structures — garages, workshops, pool houses — which run against the separate Coverage B limit

The opposite is also true and worth reporting: a new roof, a water main shutoff, an upgraded electrical panel, or a monitored alarm system typically earns a premium credit. The same phone call that corrects your limit upward can lower your rate. Most homeowners make neither call.

What to send your agent, and what to check on the next declarations page

The whole exercise resolves into one email. Send your agent:

• Your corrected above-grade square footage, and your finished basement or attic square footage listed separately
• A dated list of every renovation since the policy was written, with approximate cost and what was done
• Roof age and material, HVAC age and type, electrical panel amperage, plumbing material
• Any protective devices — water leak sensors, automatic shutoff valve, monitored smoke, fire, and burglar alarms
• A request for two things in writing: a re-run replacement cost estimate with the input sheet attached, and a quote for extended replacement cost if you do not already carry it

When the next declarations page arrives, check three things and you are done for the year: Coverage A against your current rebuild estimate, the endorsement list for extended replacement cost and ordinance or law, and the protective device credits to confirm you are receiving what you qualify for.

All of that depends on one thing — having accurate, current information about your own house. That is the actual problem here. Not carrier behavior, not policy language, but the fact that almost nobody keeps a documented record of their home's square footage, systems, materials, ages, and improvements in a form they can hand to an agent. Without it, every rebuild estimate is a square-foot guess, and the guess is usually low.

This is what Rafter is built to solve. Rafter runs an AI-powered assessment of your home and builds a documented profile of exactly those inputs — square footage, finishes, systems, roof and equipment ages, protective devices, and a dated record of every improvement and maintenance item. It produces a prioritized mitigation plan for the risks that plan surfaces, and it keeps the documentation you need to both close a coverage gap and claim the protective device credits you have already earned. When your renewal arrives, the ten-minute check stops being an estimate and becomes a lookup.

Your next step: find your declarations page, write down the Coverage A number, and compare it to your square footage times a current local rebuild cost. If the gap is more than 10%, call your agent this week. Then start the record that makes next year's check take ten minutes instead of an afternoon.