I live in Mobile, AL. My house crawlspace is wet and black mold is obvious on the wood of the pie and beam construction with venting on 3 of the 4 walls.  What inexpensive means of cleanup and prevention can I perform myself?  I am told I need a cleanup company and polyurethane sprayed in afterwards but this will cost at least $3,000, and it seems disinfectants, a crawlspace fan and plastic sheeting would accomplish the same effect.-David, Alabama                    

            Crawlspace remediation can be done by a homeowner with possibly some help from a contractor.  You have several issues that have to be addressed.  These include:  (1) mitigating the wetness/moisture problem under your house, and (2) remediating crawlspace timbers. 

            A wet crawlspace is mostly commonly due to poor site drainage from usually heavy clay soils.  I am not sure what your soils are like in your coastal town of Mobile (coastal towns often have sandy soils).  Whatever the cause the wetness problem needs to be remediated or the mold problem will return in a few years. 

            All crawlspaces should be covered with a heavy-duty plastic moisture barrier to reduce evaporation from the soil.  Crawlspace vents with adequate air movement at all times is also needed.  In some cases crawlspace vents may not be adequate to do the job.  In such cases you may have to install a fan.  If a regular-type fan is installed, it must be positioned to blow air into the crawlspace rather than exhaust it outward.  If one exhausts air using a regular fan, it will rapidly corrode.  There are fans used in radon remediation that are for the most part corrosion resistant.  These can be used to exhaust crawlspace air.

            An issue unique to coastal areas is the contribution of high humidity ambient air to moisture take-up by crawlspace timbers.  Some studies indicate that it is a significant factor in crawlspace timber moisture levels and a risk factor for mold growth. 

            On the other hand a wet crawlspace is a much greater risk for mold infestation and thus should be the major focus of crawlspace remediation. 

            The black mold you report is likely to be Cladosporium.  It commonly grows on structural timbers subject to high humidities/condensation. 

            To remediate crawlspace timbers, I recommend a regimen of vacuuming (minimum 5HP suction), brushing (stiff brush), vacuuming and spray applying a minimum of one coat of octoborate/polyborate-containing paint (i.e. www.fosterproducts.com). 

            Spray-applying polyurethane in a crawlspace has no practical value.  It may even make the problem worse by trapping moisture in timbers subjecting them to rot.  Wet polyurethane will also undergo biological decomposition.

 November 14, 2003      

 Indoor Environmental Quality (2000), Thad Godish Ph.D., C.I.H

Direct E-mail 00tjgodish@bsu.edu