Olympia Home Inspector Explains Dark Marks On Siding

Posted by on Jan 4, 2012 in Inspection Stories | 3 comments

Olympia Home Inspector Explains Dark Marks On Siding

Although I had never seen this exact situation before, it did not take long to understand what was going on with this Olympia home. These dark marks were on the  siding above all the sub-crawl area foundation vents. They are similar to the dark markings I sometimes see around roof vents on homes with moisture issues in the attic.

I knew more would be learned near the end of the inspection when I got into the crawl area. Sure enough, it was a very wet crawl area. Water under a home is never recommended. A one time event is unlikely to cause a problem but continual standing water can lead to moisture issues throughout the entire structure including the attic.

These stains are caused by moisture vapor exiting the vents, condensing on the cold siding and then growing small amounts of organic material. This happens directly above the vents because the area is kept constantly wet. Think of it as a localized Petri dish.

Olympia Home Inspector Finds Water Issue

Olympia Home Inspector Finds Water Issue

In building science terms, something called the “stack effect” can transport moisture from a wet crawl area up through a home. Because of the difference in air pressure inside and outside the home, moist air is drawn up through leaks in the structure. This can lead to mold issues, indoor air quality problems, even wood rot in the roof sheathing and framing members in the attic.

In this case it was recommended that a licensed drainage contractor evaluate the structure for the changes needed to dry out the crawl area and to keep it dry. This may require measures such as re-directing downspout water away from the foundation, re-grading of soils next to the home to direct water away, the addition of a sum-pump or curtain drain around the home.

If you have water under your home, act quickly and have it resolved. If you suspect a water issue but want a professional Olympia home inspector to evaluate it, please call our office or use the online scheduler to set up an appointment. 360-561-0951

Sound Choice Inspections

Your Olympia Home Inspector





One Response to “Olympia Home Inspector Explains Dark Marks On Siding”

  1. Barb Muirhead says:

    Thanks George for your help on this one. We’ll see what we decide to do.

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