Is It Better to Have 80% or 100% Coinsurance?
100% usually costs less in the long run, since it means insuring the house for its full rebuild cost, not less.
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The coinsurance number isn't something you pick like a deductible. It's a requirement that your dwelling coverage equal the full rebuild cost of the house, usually 100% of it. If you insure for less, say 80% of what it would actually cost to rebuild, the insurer can reduce any claim payout by that same shortfall, even on a partial loss like a kitchen fire. So the choice in front of you is about setting dwelling coverage correctly at the start. A contractor's replacement cost estimate, not the sale price, is what gets you there.
Getting the dwelling number right matters more than the price
Two policies with the same price can pay very differently if the dwelling coverage is wrong on one of them. Compare quotes side by side and check that each one is built on a real rebuild cost estimate, not a shortcut.
How is the rebuild cost figured out, and who does it
The number used for dwelling coverage comes from a replacement cost estimate, not an appraisal and not the price being paid for the house. An appraisal values the land and the structure together for a sale or a loan. Replacement cost looks only at what it would take to rebuild the house itself at current material and labor prices, which is a different number and often higher than people expect, especially in areas where construction costs have climbed.
Most insurers run this estimate themselves during the quote, using a model that factors in square footage, the number of stories, the type of foundation, roofing material, and finishes. Some will send someone out to look at the house, particularly if it's older or has features that are hard to judge from a form, like a renovated kitchen or an attached guest unit. Either way, the estimate becomes the starting point for the dwelling coverage number on the policy.
It's worth checking that number against the details of the actual house. If the estimate assumes a smaller square footage than what's in the listing, or misses a finished basement or an addition, the dwelling coverage will fall short of 100% of rebuild cost without anyone intending it to. The listing sheet, a recent inspection report, or the builder's specs if the house is newer are useful to have on hand when getting the quote, since they let the estimate reflect the house as it actually is rather than a rough average for homes its size.
Rebuild costs also change over time, through inflation in materials and labor, so the number that was accurate at closing may not stay accurate for years. Some policies include a built-in adjustment that raises dwelling coverage automatically with construction cost trends. It's listed on the declarations page, and if it isn't there, the dwelling number is worth revisiting at each renewal rather than assuming it still matches what rebuilding would cost.
What happens at renewal if rebuild costs change
The dwelling number set before closing is not permanent. Material and labor costs move year to year, sometimes a lot in a short stretch, and a figure that matched 100% of rebuild cost at closing can quietly fall short two or three renewals later. This matters because the coinsurance requirement is checked against the rebuild cost at the time of a claim, not the figure that was accurate when the policy was first written.
Most insurers send a renewal notice that keeps the same dwelling coverage unless something prompts a change, like a renovation reported to them or a built-in inflation adjustment doing its work in the background. That adjustment, sometimes called inflation guard, raises the dwelling number automatically each year based on construction cost trends for the area. Whether a given policy has it is listed on the declarations page, usually near the dwelling coverage line, and it is worth checking rather than assuming.
Without that adjustment, the dwelling number only changes if the homeowner asks for a new replacement cost estimate or the insurer happens to reassess it. A kitchen remodel, a finished basement, an addition, any of these raise what it would cost to rebuild the house, and none of them show up in the coverage automatically. The homeowner is the one who knows the work was done, so it falls to them to report it and ask for the estimate to be updated.
A quick way to check is to compare the dwelling coverage on the current declarations page against a recent estimate of local construction costs per square foot, which contractors and some insurers can provide. If the gap looks large, a call to ask for a new replacement cost estimate is worth the time. Letting the number drift is how someone ends up fully intending to carry 100% coinsurance but discovering, after a loss, that the house would actually have cost more to rebuild than the policy assumed.
Before you sign anything
Check the dwelling coverage number against a real rebuild cost estimate for the house, not the sale price. If it looks low for the square footage, ask for that number to be corrected before closing.
