Outdoor Sources of Excess Home Moisture

by J on December 22, 2010

It’s fairly straight forward identifying if you have a moisture problem in your home. What’s not so straightforward is narrowing down what is causing the moisture problem. Previously, we considered indoor sources of excess moisture in the home. Today let’s consider exterior moisture sources that can cause problems inside the house. The Oregon State University Extension Service Home Moisture Problems handout is a valuable source of information for homeowners.

Common Outdoor Sources of  Moisture Problems

  • Foundation Drainage. If moisture problems suddenly develop in your home, suspect a problem with your foundation’s drainage. Two common sources of foundation drainage problems are plugged downspouts and blocked foundation footing drains. Another problem area could be the slope of the ground around your foundation. Ground that slopes toward your home needs to be corrected. Assess the severity of it, and if the scope of the remediation is beyond you, hire an excavation contractor to regrade your land so that it slopes away from your house. You may also want to consult with a basement waterproofing expert to help determine the severity of the problem.
  • Slabs. Neglecting to install a moisture barrier underneath a slab can cause moisture to wick up through the slab, creating problems in the house. This is often the problem in converted garages with excess moisture.
  • Below-grade walls. If you have a cement block foundation, moisture may move up through the blocks, causing problems in the walls, which raises the humidity levels in the house.
  • Splashback. Moisture problems can occur when your siding is installed too close to the ground. If the siding is less than 12 inches from the ground, rain can splash up and soak the bottom edge of the siding. At this point, capillarity can take over and the water can move into the wall. One home improvement fix to this problem is to paint and seal the bottom edge of the siding to waterproof it.
  • Details. Construction problems like inadequate drip edges and flat edges can allow moisture into the home. Check your roof for problems. Old or missing shingles and missing flashing around chimneys can cause water damage inside the home.
  • Air flow. Be sure to let the air circulate around your home without any obstructions. Trees and shrubs that touch your home or firewood that is piled up against the house can all cause moisture problems. You should allow a few feet of space between your house and any shrubs or piles of firewood.

Being vigilant about checking for moisture problems in your home can help you identify a problem in the early stages before it is allowed to do years of damage. Be sure to call in an expert, such as a basement waterproofing professional, if you’re unable to determine the source of the problem.

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