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▼ Is Your Crawl Space Up To Code?

The Uniform Building Code requires the following:

  • All Crawl spaces must have an entry of 20" x 24".
  • A minimum of 18" clearance below joists and 12" below girders (large beams) is required to allow room for movement.
  • For proper ventilation and air circulation the crawl space must have openings or vents in a ratio of 1 sq. ft. for each 150 sq. ft. of floor above and should be covered with a 1/4" screen mesh.
  • Code requires wood and earth to be separated by at least 6 inches.
  • The soil in a crawl space must be comcovered by a vapor barrier which is simply plastic sheeting - 6-mil polyethylene

The code makes no effort to establish maximum standards.  For that reason you must realize that compliance with the Uniform Building Code may not be adequate because of unique characteristics in each home.  A house constructed on soil which allows for good migration of water such as a sandy formation at the top of a hill may be well served by a crawl space 18" deep where the water evaporating into the air and being carried out through the vents is minimal.  Conversely the same house at the bottom of a hill or on a reverse slope (soil sloping toward the house rather than away) may be burdened with substantial more water coming from the soil into the air in the crawl space and the minimum clearance and vent openings may not keep the crawl space dry.  Code enforcement officials are allowed to use their own opinion to deviate from standards regarding crawl space venting which has resulted in tremendous variation in crawl space ventilation around the community.   

What does this have to do with mold? 

The key to mold prevention is to keep moisture out of the crawl space while providing proper ventilation, thus eliminating an atmosphere where mold spores will settle and colonize.  You may think that mold contamination in a crawl space can't pose much of a problem but if left alone over a certain period of time mold colonies can eat away at the wood which will eventually compromise the safety of the structure.  Repairs for this type of damage will be costly.  Mold contamination in a crawl space has the potential to affect  the indoor air quality of the main floor of the structure and is hazardous to humans with sensitivity to mold or those with immune system deficiencies.  Water intrusion into a crawl space that is left unnoticed can result in moisture actually vaporizing and passing up through the other floors of the house; this can elevate the indoor humidity level and also condensate on the attic ceiling that can in time possibly initiate mold growth in that area of the structure. 

  • Check your crawl space regularly for water issues
  • Make sure you have a good vapor barrier in place
  • Inspect around the foundation for drainage problems
  • Inspect vents and keep plants and debris from blocking them                                                                                       
  • Take care of water intrusions immediately                                                                                                                        



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