As the waters from Hurricane Harvey recede in Texas and Louisiana, the owners of more than 100,000 flooded homes are getting a good look at what is left.
“The damage to the houses is going to be tremendous,” said Jean-Pierre Bardet, a geotechnical engineer and dean of engineering at the University of Miami. Thousands are beyond repair.
Often, however, a waterlogged house can be saved.
“A high water depth doesn’t mean the home is destroyed,” said Claudette Hanks Reichel of Louisiana State University’s Agricultural Center, who has written disaster recovery material for the U.S. Department of Housing and Urban Development. “But if a house was already structurally compromised by decay, termites or very poor construction, then the flood could be the last straw”
So what does water — not a small leak but a major deluge — do to a house?
Cracks the foundation
Serious foundation damage is common in Southeast Texas and Louisiana, Reichel said, because the soil is mostly clay, and most homes are built on concrete slabs. Saturated clay expands unevenly and lifts parts of a slab, causing it to crack or break. Embedded pipes can rupture, exterior walls can crack, the roof can sag. As the soil dries and shrinks, it all gets worse. Sometimes, moving water erodes the soil from below the slab, and a poorly secured house will simply float off its foundation. No one should enter a house that looks cracked or off-kilter before a structural assessment.
Jams (or breaks) windows and doors
Bardet said one of the first signs of foundation damage is that doors and windows won’t open or close because their frames have become distorted by the shifting house, sometimes so much so that the glass twists and breaks. Glass could also be broken by floating debris.
Water weakens regular drywall, and the paper facing provides food for mold, Reichel said. If drywall is soft, crumbly or moldy, it has to be replaced. Plaster and other materials may dry, but walls and ceilings that were in contact with water still need to be gutted down to the framing so that the insides can be cleaned and dried to prevent mold.
Most insulation used in homes is made of fibers or foams that hold water, so it has to be replaced if it gets wet. But other types, such as closed-cell foam, don’t absorb water and can survive a flood.
Many common types of structural sheathing — the large panels between the framing and the outside of the house — are a composite of wood chips or other porous material. Those will absorb water, swell and lose strength. Plywood sheathing probably will be fine after it dries out.
Temporarily swells framing
Here’s some good news: Most homes are framed with solid wood lumber, which usually withstands flooding quite well unless it sits in water for weeks or was already damaged. Even if the wood soaks up some water and swells, it should return to shape and maintain its structural integrity. All framing has to be cleaned thoroughly and dried quickly to prevent mold, which flourishes in warm, moist areas.