Causes

• Black mold, or Stachybotrys chartarum, requires water to grow. A water leak can introduce enough moisture inside a wall to allow black mold to grow and spread undetected, according to the book "Home Rich," by Gerri Willis.
  
  

Issues

• Not all forms of black mold are toxic, but Stachybotrys chartarum is associated with health issues in people exposed to it, including allergic reactions and respiratory difficulties. The more black mold in a home and the longer the exposure continues, the worse the health issues can become, according to the book "Nevada Real Estate Principles and Practices," by Harry V. Eastlick.
  
  

Solutions

• Finding and fixing water leaks quickly is key to reducing the risk of black mold growth. After a water leak, wiping damp surfaces with a detergent can eliminate mold spores if the surfaces are thoroughly dried afterward. In a worst-case scenario, entire sections of an affected house will need to be torn out and replaced to be sure the black mold is gone.