What Is Rising Damp?

rising damp

“Rising damp” may sound like the name of an Eighties metal band. However, it’s actually a phenomenon that occurs inside homes which can cause noticeable water damage as well as impact the overall health of the indoor environment. Expressed simply, rising damp is moisture that is absorbed upwards into the structure of a home from an ongoing source of wetness somewhere below.

How Does It Happen?

Moisture accumulating underneath a structure may be drawn upwards into certain absorbent building materials, most notably drywall, plaster, and masonry. Think of it as the effect of water being sucked up by a dry paper towel.

Where Does the Moisture Come From?

Groundwater rising up beneath the house keeps the crawl space underneath chronically wet. This moisture may be gradually soaked up into structural materials above.

A chronically wet basement due to seepage from outdoor soil, frequent flooding, or even plumbing leaks, may also provide a water source that migrates upwards into the structure.

What Are the Consequences?

Rising moisture content inside building materials gradually deteriorates the material. You may first notice that affected walls always feel damp. This typically progresses to flaking paint, peeling wallpaper, and eventually decomposing, stained drywall.

Chronically damp building materials indoors also provide a focal point for mold growth. Airborne spores released by growing mold spread contamination throughout the house and may trigger allergic reactions in susceptible individuals.

How Can It Be Treated?

Eiminate the moisture source.

  • The crawl space should have a plastic cover installed atop the soil to prevent intrusion of rising ground moisture, as well as adequate ventilation.
  • Reduce seepage through basement walls by grading landscape to divert pooling rainwater away from the house perimeter. A french drain installed in the ground can also remove excess soil water. Seal obvious cracks or leaks in basement walls that admit water.
  • Water permeating through the basement floor can be removed by a sump pump.
  • Identify and repair plumbing leaks.

Chronically moist and/or moldy sections of drywall in the house may be unrepairable. However, they can be cut out and replaced with new material.

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