Mold 1. Problems

What About Mold from Moisture Problems in Buildings

We expect that molds growing on damp surfaces indoors can get airborne.


We find these moldy or conducive conditions indoors:

  • Moldy window sills, from moisture condensation on glass or on metal frames.
  • Moldy bathroom or bedroom walls, more on exterior, or behind furniture.
  • Moldy, water stained, or wavy walls or ceilings below leaks.
  • Moldy attics, often on large areas under the roof, from condensation.
  • Moldy odor in basements (damp? carpet?) or in cabinets below sinks.
  • Mold or water stains with white “efflorescence” salt crystals deposited on masonry.
  • Moldy crawl spaces from poor drainage, bare soil, poor ventilation.
  • Rotted wood from slow leaks around tubs, showers, toilets, or roof eaves.


We see spots or fuzzy growth on surfaces.

  • Mold spores land on surfaces everywhere, just waiting for moisture to grow.
  • Mold growth indicates excessive moisture that permits amplification.
  • Mold indoors is usually limited by water availability (also needs food & light).
  • More mold grows inside windward S & W walls near Puget Sound from rain & leaks.
  • More mold grows on the N side walls and attics near Puget Sound (away from the sun, so cooler, more condensation; and driven by the prevailing wind).
  • Mold colonies start from seedlike “spores” or fragments, and grow out rootlike threads to form circular spots, then a mat of “mycelia” or “mildew”.
  • Outdoor molds grow on living and dead matter, and in soil.


We should fix moisture or 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).
  • Breathing airborne allergenic mold particles can cause health problems.
  • Other fungi are less of an air concern: mushrooms, yeasts, rusts, smuts.


We have moisture and water intrusion from indoors and outdoors from many sources.


We must avoid conditions conducive to moisture, surface molds, or WDOs, such as:

  • Damp materials.
  • Moisture condensation.
  • High humidity.
  • Inadequate ventilation.


We inspect a structure to find or evaluate if and why it might have problems.

  • Purpose: to find signs of water damage and mold growth, to guess possible sources/causes, to decide if it’s a past problem, or significant, active, and increasing.
  • Mold odor is useful evidence of damp mold, pointing to a source or a pathway.
  • Moisture can be measured within building materials using conductivity meters.
  • Water stains or rust are important flags and evidence of conducive conditions.
  • Inspectors reporting on conducive conditions in real estate transactions must have a License as a Structural Pest Inspector from the State Department of Agriculture.
  • Our inspections are limited to surface mold and conducive conditons (not a complete WDO inspection that includes wood rot or insects).
  • Wood rot fungus often has stringy white mats or “brown cubical rot”, and soft wood.


We find a few of the many natural molds growing indoors.

  • “Mold” includes thousands of species of filamentous mycelial fungi like mildew.
  • Molds are a normal component of house dust (less than 1%).
  • Molds are the microscopic plantlike version of mushrooms.
  • Some types grow mostly outdoors; their spores are often found indoors.
  • Mold types that grow in the wettest conditions may be worse for humans.
  • The type of mold usually does not change how we deal with it. It’s “just mold”.
  • These surface molds are not the structural wood destroying organisms (WDOs).


  • 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 test to confirm some hypotheses we have guessed after inspection.

  • Mold odor can indicate the presence of hidden damp growth.
  • Test the air (at least 3 locations, including outdoors) to find what we are breathing.
  • Test. before/after cleanup, or for reassurance even though no mold was found.
  • Test the growth to confirm it is mold, if it is uncertain (stain?).

NEXT:  2. Mold Inspections

©2004-2016 Richard Knights, Blue Sky Testing Labs, Seattle,