Whether the water leaks from a leaking roof, a fridge, a shower, or a burst pipe, it typically ends up under the floors and into the walls. As we explain below, this is mostly a problem for drywall, flooring, gas operated equipment, electrical equipment, and the electric system.
Most walls and ceilings are made of drywall, with a few notable exceptions, such as concrete walls in an unfinished basement and cement board in the walls immediately surrounding a shower or bathtub. Drywall quickly absorbs and retains moisture, and becomes a source for mold growth. Drywall that has been wet, should be replaced. Opening up the walls has the additional benefit that the wooden frame of the house can dry out.
If water has passed through an insulated wall or ceiling, the insulation might be affected as well. It’s best to remove the insulation so the frame of the house can dry. Most insulation materials do not retain moisture and can be reused if fully dried and if no mold has formed.
The wooden frame of a house is typically not affected by water damage, unless exposure over a longer time period has led to wood rot. It might give you comfort to know that the same frame was exposed to rain during the construction of your home, and dried up after the roof and windows were installed. However, it is important to expose the wood by removing drywall to allow it to dry.
Hardwood floors can start “cupping” after being exposed to water. This happens when the bottom of the planks absorb moisture and expand, while the sealed tops do not. When this happens, the floor typically needs to be replaced.
The grout lines of tile floors can develop cracks if the substrate below the tiles expands.
When water might have been in contact with electrical devices or the electrical system of your home, it is recommended to have an electrician inspect the damage. If the breaker panel or receptacles are still wet, you should call a 24/7 emergency electrician. Any electric devices exposed to water should be replaced. There are mixed opinions on whether the electric wiring that runs through the walls needs replacement. The NM-B wiring typically used is not rated for wet locations, and manufacturers recommend replacing it when it gets wet (National Electrical Manufacturers Association, Report Evaluating Water-Damaged Electrical Equipment, Section 4.6):
When any wire or cable product is exposed to water, any metallic component (such as the conductor,
metallic shield, or armor) is subject to corrosion that can damage the component itself and/or cause
termination failures
However, in the aftermath of the 2013 hurricane Sandy, the New Jersey department of community affairs issued guidance that if wiring has been underwater but does not appear damaged, it does not need replacement. This guidance did not discriminate between fresh water from rain and salt water from coastal flooding. The guidance is corroborated by reports from electricians who say they do not care if the wiring they carry in their truck gets rained on. Insurance companies do not typically pay to replace undamaged wiring, but are likely to pay for a megohm test that would detect certain types of damage. Your electrician can tell you whether this test is warranted.
Gas-fired or oil-fired appliances should be repaired or replaced after exposure to water. This includes furnaces, cook tops, ovens, and HVAC systems. Water can affect safety valves and burners, which can lead to gas leaks or fires.