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Moisture In Your Crawl Space



Crawl space moisture damage

High moisture levels in the crawl space can cause many problems in a home.


During a home inspection, if signs of abnormal moisture are detected, the home owner

should make corrections to the home as soon as possible. This may require hiring a

contractor who specializes in crawl space moisture control.


High moisture content in crawl spaces will eventually lead to serious damage.


Two different types of damage are typical:


  1. If the moisture source is directed at a foundation wall, such as from a gutter downspout, the foundation wall can suffer major damage such as sinking, cracking, bowing and deterioration.

  2. High moisture content in a crawl space damages insulation, creates a perfect environment for fungus to grow, allows termites to prosper and can eventually cause wood to rot.


Let’s take a look at an example where a gutter downspout contributed to cracking of a

foundation wall in a Raleigh, NC home. The lot was gently sloped from the front to the

rear and a downspout was dumping at the front of the house, just right of center. The

ground at the front of the home was flat so water exiting the downspout accumulated

here. Not only did water accumulate, it ran through the foundation wall, under the house

and exited at the right rear.


When this house was inspected, it was only six years old yet the foundation wall at the

right front, right middle and right rear was cracked. Basically, the right side of the house

had dropped. The crack at the right rear was about one-half inch wide. This was a costly

repair that involved consultation with a structural engineer.


The moral of the story here?


Gutters are not enough; the home owner must ensure the downspouts direct water well

away from the home.


A discharge point of 10’ from the house is a good rule. This can be accomplished with

landscaping drain pipe on top of the ground covered with mulch/pine straw, a buried

landscape pipe or a buried PVC pipe.


Now, the other issues – mold, termites, rotten wood and damage to insulation. Insulation

absorbs moisture then becomes heavy, begins to deteriorate and ends up falling on the

ground. Damp wood framing members are a perfect place for molds to flourish.


These molds can enter the interior of the house as the crawl space air does exchange with the inside air (that is another subject for another time). And, we all know termites need

moisture to survive, they love to consume wood and damp wood is a playground for them.


Lastly, if high moisture levels continue to long periods of time, wood framing members

can decay.


During a recent home inspection, it was discovered that a screwdriver could

easily be inserted a half-inch into much of the framing.


Repair costs were significant as additional bracing had to be added to support the weakened framing.


We could elaborate on each of these individual topics as the ramifications of a damp

crawl space are significant.


Further, drying of the crawl space, mold remediation, grading of the soil, etc can become very detailed.


But for now, just remember to check those gutter downspouts and consider their potential effect on the life of your home.

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