Basement Leaks and Moisture

From time to time, virtually all homes with basements will have moisture problems or direct leaks in areas below grade. This does not necessarily mean that the home is poorly constructed.

Usually the problem is caused by improper grading that prevents water from effectively draining away from the foundation. Experience has shown that faults can also develop when gutters and downspouts get clogged, depositing unusually large quantities of water on the ground near the home.

How to recognize leaks or moisture problems

A leak is usually obvious, but other moisture problems can sometimes only be detected indirectly, such as finding mold (sometimes hidden by interior finishes) or detecting musty odors (usually when the area has been closed for a period).

Where does the moisture come from?

Outright leaks can occur under specific conditions, especially in early spring when melting snow can’t penetrate the frozen soil but finds its way down the side of the foundation where heat loss has made the soil permeable. Seepage, which is just a slow leak, can occur in the fall or spring when heavy rainfall or melting snow causes the ground near the foundation to become saturated. Homes built before 1950 seldom have weeping tiles to draw water away from the foundation, and in homes more than 20 years old these tiles may no longer be effective due to deterioration.

A significant source of basement moisture is condensation. When the basement air is humid, moisture will condense on cool surfaces, such as cold water pipes, foundation walls or the floor slab.

The telltale signs of moisture

  • a musty odor
  • a white powdery mineral deposit on masonry or concrete walls (this is called efflorescence)
  • stains, discoloration or decay on window sills, sill plates, wood posts or even furniture or cardboard boxes stored in the basement
  • bulging or lifting drywall tape, popped nails, bubbling or peeling paint and detaching wallpaper
  • rust at the base of heating equipment, steel posts or appliances
  • lifted floor tiles, buckled paneling, mildew on carpet