Slate's Explainer: What Flooding Does to Homes

Slate senior editor Andy Bowers explains what kind of damage floods do to homes. For homes left completely under water, the cost of repair will probably exceed the cost of moving out.

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Along with the big reconstruction issues, everyone from New Orleans is wondering when or if they can ever move back home. The Explainer team at the online magazine Slate has been looking into a basic question about this: What kind of damage does a flood do to houses? Here's Slate's Andy Bowers.

ANDY BOWERS (Slate): It depends, of course, on the severity of the flooding. For homes that are completely under water or that are flooded to the upper floors, the cost of repair will probably exceed the cost of moving. At the very least, the interior finishes of a waterlogged house must be stripped and replaced. High water can also damaged the wiring, gas lines, furnace and septic system, not to mention furniture and appliances.

Wind and water can cause a house's structural components--the struts, studs and foundation--to shift or warp. Tilting walls or a shifted roof also suggest dangerous structural damage that could signal an imminent collapse.

Inside the house, ceilings may sag under the weight of trapped water or soggy drywall. Wet floorboards bend and buckle, and the roof may leak or break altogether. Flooding in the basement can be especially dangerous. If the water is removed too quickly, pressure from the soaked earth outside can push inward and crack the foundation walls.

Brick and masonry homes will suffer less exterior damage than those made of wood. In all types of housing, though, flooding will most likely destroy the interior walls. Studs will eventually dry out and return to their original shape, but any plywood in the walls is likely to swell and peel apart. Water can also dissolve the mortar in a chimney, which creates leaks and thus a risk of carbon monoxide poisoning once the heat comes back on.

Structural hazards account for only one kind of water damage. Floods often deposit dirt and microorganisms throughout the house. Silt and sediment can create short circuits in electrical devices, and anything that gets soaked through with water may contain sewage contaminants or provide an almost irresistible breeding ground for mold.

CHADWICK: Andy Bowers is a Slate senior editor. That Explainer was compiled by Daniel Engber.

Slate has several other very good articles on Hurricane Katrina and the aftermath, and there's other information at our Web site,

More on DAY TO DAY just ahead. I'm Alex Chadwick.

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