Crawlspace Mold Growth

We recently purchased a new home and within 2 weeks time noticed water had been sitting in the crawl space.  As we checked further, mold had started to grow under the crawlspace.  As far as we can see, it is only under the plastic that was laid on the ground.  What actions should we take to correct this?  Is the builder at fault?  How can we prevent this from happening again?  What actions should we take with the builder?  How can this affect the health of my family?  Should we have another inspection done for mold on the home and who should pay for the services?-Erin , Tennessee

            Water sitting under the crawlspace, even if only seen under the plastic “earth cover” is likely to pose significant problems for whoever is the homeowner.  It is an indication that the building contractor did not prepare the building site to provide adequate drainage.  It is in fact the builder’s fault.  Some building scientists would say that builders often choose to use crawlspace substructures in lieu of providing proper drainage.

            Despite water being under the plastic, there are several ways it can result in elevated humidity levels in both the crawlspace and the house.  This would be the case if the plastic did not completely cover the ground surface, had cracks in it, etc.  Water from wet soil also commonly wicks up crawlspace footers and cement (or concrete) block where it vaporizes into the crawlspace resulting in elevated humidity levels above the plastic ground cover.  This wicking phenomenon is quite common .It can be seen in the following image.

crawlspace wicking.pdf

            With time elevated (>70%) crawlspace humidity will cause a variety of mold species to grow on crawlspace timbers.  Mold spores from these infested timbers can then pass into supply air ducts passively by convection when heating/air-conditioning units are not running.    This can result in elevated airborne mold levels in building spaces.  It can also result in an earthy, musty odor.

            If family members are sensitive to mold types present or have the potential to do so, then a moist crawlspace is likely to contribute to significant mold exposures and respiratory health effects such as chronic allergic rhinitis, sinusitis, and/or asthma.

            Your house appears to have a major problem with moisture that needs to be addressed before it evolves into a mold problem, then a health problem.  It is the builder’s responsibility to have constructed the house properly and he/she should be called on to install a drainage system around the periphery of the house to reduce moisture levels.  If you can’t get the builder to do it, I recommend your going ahead yourself to head off a highly likely mold infestation problem.

            I don’t think you need to have another inspection done.  You already know that you have a problem that will only become worse with time.

 

October 6, 2006