Mold growth

Problems with surface mold growth can usually be seen and smelled.


  • We see spots or fuzzy growth on surfaces.
  • We find moldy window sills, walls, attics, basements, below sinks.
  • Mold growth indicates excessive moisture that permits amplification.
  • Mold indoors is usually limited by water availability (also needs food & light).
  • Mold colonies start from seedlike “spores” or fragments, and grow out rootlike hyphal threads to form circular spots, then forms a mat of “mycelia” or “mildew”.
  • Mold odor is useful evidence of damp mold growth that is active (not dry, dormant).


  • We expect that molds growing on surfaces can get airborne.
  • We should fix mold problems, and avoid airborne mold.
  • Mold growth indicates a problem with moisture, and maybe other wood destroying organisms (WDOs) such as wood rot fungus or insects (beetles, termites, ants).


  • Mold throws out spores when mature, when humidity is high enough.
  • Mold particles (spores and mycelial fragments) get airborne when disturbed.
  • Disturbing dry mold can release much of it into the breathing air.


  • We find a few of the many natural molds growing indoors.
  • Some types grow mostly outdoors; their spores are often found indoors.
  • Mold types that grow in the wettest conditions may be worse for humans.

>see also Mold & Moisture

Mold & Moisture Problems in Buildings

The following pages are details about “Mold and Moisture Problems in Buildings“:

  1. What About Mold from Moisture Problems in Buildings
  2. Mold & Moisture Inspections in Buildings
  3. Mold Hypothesis Testing in Buildings
  4. Mold Testing: Results & Analysis
  5. Avoiding Mold Growth in Buildings by Controlling Moisture
  6. Cleaning Up Mold & Rot: Building Remediation

©Richard Knights, Blue Sky Testing LLC
Salem, OR & Seattle, WA,