Begin by visually scanning the walls and pay extra attention to the high-probability locations noted above. Look for any discoloration, change in the wall texture or a slightly wavy surface, and peeling or powdering paint. Push on any suspicious areas with your finger, looking for soft spots.

    Then feel for moisture. Fingertips are your own exquisitely sensitive on-board moisture detectors. A folded piece of toilet paper pressed against the suspicious surface is another good moisture indicator.

    Your nose can also lead you to the problem area. A musty odor in one part of the home indicates a definite problem. Removing a nearby switch or outlet cover plate may give you a small opening to sniff the inside of the wall cavity.

    Wet areas of wood exterior siding will have the same visual clues for moisture, but we suggest probing any suspect spot with a screwdriver because wood is sturdier than drywall. Wet and rotting wood will crumble when poked.

    Home inspectors like us take the search for hidden moisture a step further by using electronic tools. Here’s the four we carry in our tool kit:

  1. Bullet Infrared camera - It sees heat instead of light, and creates an image on a screen that shows temperature variations over surfaces as shades of gray or a gradient of colors. Because the continuous evaporation that occurs on a moist surface makes it slightly cooler than surrounding dry areas, this tool is great for scanning large areas for moisture intrusion. It is not as useful on the exterior of a home, because of the temperature variations between sunlit and shaded surfaces.

  2. Bullet Non-invasive moisture meter - When this device is run over a wall surface, it sends a radio frequency signal that penetrates the material for a moisture level reading.

  3. Bullet Pin-type moisture meter - When two small pins at the head of the meter are pushed into the wall it uses the electromagnetic resistance of the current flow between the pins to determine moisture content, because wet materials allow more current flow. This system is low-level invasive, due to the tiny pin holes left in the material. Although we use a professional model that costs serval hundred dollars, Home Depot offers an inexpensive version for homeowners, manufactured by General Tools, for under $20.

  4. Bullet Borescope - It has a tiny camera and light, only 1/3” in diameter, on the end of a flexible cord that sends an image to a laptop computer, allowing examination of the interior of a wall through a small hole. We are using it in the photo below to examine the interior of a dryer duct. The insulation that fills the wall cavity of exterior walls can limit the usefulness of this tool.

    Even with the advantages provided by these high-tech gadgets, the best and final way to evaluate moisture damage in a wall is to open it up where you found the problem, and continue expanding the opening until you reach the edge of affected area. Exterior walls can be the most problematic, because the wall insulation absorbs the water and spreads it in all directions by capillary action.

    Mold can begin to grow as soon as 48-hours after building materials get wet. If it is not yet visible on the wall surface, opening up the wall is the only sure way to determine the presence and full extent of any mold infestation, and the moisture-damaged wall material will have to be replaced anyway.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
© McGarry and Madsen Inspection


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