Water stains are an indication of a water problem (which makes it possible for further mold growth). Unfortunately, not all water damage is easily visible. Water damage can be present within walls, underneath floors, and on ceilings. Evidence of small, ongoing leaks may not be visible until the mold has begun growing. Still, there are a few things to look out for: peeling or bubbling wallpaper & paints, curling or bubbling vinyl flooring warped wooden floors, yellow, brown, or copper-colored stains. Irregular stains may be an indication of mold growth. Some molds stain the surface on which the mold is growing, which leaves a black or blue-black colored stain. Mold growth will cause further damage to the material it is growing on and can ruin wood integrity.