Flood insurance

Flood insurance covers damage from rising water, surface water and mudflow — perils every standard homeowners policy excludes. It is a separate purchase, and for property in a designated high-risk zone, a lender requirement.

The exclusion that makes it necessary#

Standard property policies cover water damage originating inside the building and exclude water arriving from outside.

A burst supply line is covered. A river over its banks is not. Surface water running down a hill into a basement is not. Sewer backup is generally not, without a specific endorsement.

That line — inside versus outside — is the source of a very large share of denied claims after a storm, and homeowners routinely discover it while standing in a flooded basement.

Where it comes from#

Most residential flood coverage runs through the National Flood Insurance Program, with a growing private market alongside it. Private policies sometimes offer higher limits than the programme's caps.

The waiting period#

New coverage typically does not take effect for thirty days, with narrow exceptions including policies bought in connection with a loan closing.

This is deliberate and it is absolute. Flood insurance cannot be bought in response to a forecast, and every year people try.

What it does not do#

Three limitations catch claimants.

Caps. Programme coverage is limited, and on higher-value property those limits can fall well short of the loss.

Basements. Below-grade areas are treated restrictively. Structural elements and some systems are covered; finished walls, flooring, furniture and personal property in a basement are largely not.

Contents are separate. Building coverage and contents coverage are bought independently. An owner with building coverage only has nothing for the belongings.

Zone maps describe probability, not safety#

A high-risk designation triggers the lender requirement. It does not mean property outside the zone is safe, and a meaningful share of claims come from outside high-risk areas.

Maps are also revised. A property can move into a high-risk zone through remapping without anything about it changing, at which point the lender requires coverage that was previously optional.

In Minnesota#

River flooding on the Mississippi, Minnesota and Red River systems drives most mandatory coverage in the state, and spring snowmelt is the recurring cause rather than tropical storms.

For property near any of those systems, checking the current zone designation before buying is worth the few minutes — both because coverage is a real annual cost and because it belongs in the purchase arithmetic rather than arriving after closing.