Moisture Ants—the home inspector’s little helper.

One of the wood destroying insects that Washington State, Licensed Structural Pest Inspectors report on is “Moisture Ants.”

These fascinating ants are considered a “secondary” wood destroying organism.  In other words they typically only infest wood structures that are already damaged by wood fungal rot.  They like to build their nests around the damp wood which then acts like a sponge to make even larger areas of wood wet—thus promoting further decay.

The key with these critters is that there has to be a good source of water.  Plumbing leaks fit this bill very nicely.  For example a failed pipe fitting might have a very small leak that has damaged the wood below it.  The moisture ants will build their nest in the decay and might then extend the nest to totally encapsulate the leaking pipe.  The nest would then have a constant supply of moisture to support the colony.  In this manner whatever is covered with the nest would be subject to decay/rot.  The size of the colony would be relative to the supply of water.

Sometimes we see areas of obvious past infestation but perhaps the moisture condition is no longer present or is seasonal.  In some instances they come and go relative to the presence or absence of adequate moisture.  So in this sense they can assist the home inspector in finding other conditions. Whether active or not there can still be damage that needs to be repaired.

In this first picture we can see where the Moisture Ants have built a nest up into the wall cavity behind an electric base board heater.  (I think you should be able to see the outline of the heater on the wall around the damaged area.)  The source of this moisture was at a plumbing leak in the crawl space below.  Some of the materials of the nest appeared to be made out of the blown cellulose insulation that was in the wall cavity.

Pulling out some of the nesting material you can see where the wet nest made the exterior siding wet creating decay which could then be used by the ants for further nesting materials.   Can you see the bright lighted holes at the center of the picture?

These holes are where the boards have become so thin that the outdoors is now visible through the holes.

Here is a picture of a piece of the nest pulled from the wall.

And a “close-up” of the Moisture Ant “carton” or nest.

I think you can now see why the Moisture Ant can be seen as the “Home Inspector’s Little Helper.”

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Charles Buell, Seattle Home Inspector

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