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  1.    The list is longer for stains that start in the attic. If the refrigerant lines to the air handler (indoor unit) of your air conditioning system run through the attic, any areas of missing or damaged insulation will sweat profusely during hot and humid summer months. Sometimes the attic insulation will absorb it and allow the wetness to evaporate before reaching the ceiling except during the hottest time of year. Leakage of cold conditioned air at the seams of duct connections, especially when they are on the bottom of the duct and just above the ceiling, will also cause condensation and a wet stain.

  2.     Plumbing leaks are another possibility. While a leak in a water supply pipe in the attic or floor framing of an upper floor can cause staining, it usually makes a big mess quickly and is easy to identify. But pinhole leaks, especially in older copper pipes can be tiny enough to create a wet stain and some mold growth without flooding an area. Drain piping is the more common type of leak. A stain that is directly below a bathtub or toilet needs further investigation by a plumber.

  3.     An old container of stored liquid in the attic that has corroded through or been knocked over might be the cause or, rarely, rodent urine directly under a nest will be it.

    A wet stain can be tracked back to the source by a home inspector with any of several different moisture detection tools, such as a infrared camera, electronic moisture meter, or just probing the area with finger tips for wetness. But dry stains can mystify even the best inspector, and may indicate a previous moisture intrusion problem that already been fixed. Sometimes we just have to say “Gosh, don’t know what caused it, but the area is dry now. If the stain comes back after you repair the area, let’s try to troubleshoot it again.”

    When you repair the stain by painting over it, we recommend starting with a coat of an oil-based stain-blocker paint, like Kilz Original or Kilz Complete, before applying a the matching ceiling color. Most water-based paints will allow the stain to migrate to the surface over time and annoy you all over again.

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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