Mold 2. Inspections

Mold & Moisture Inspections in Buildings

  • Purpose:  to find signs of water damage or mold growth, to guess possible sources/causes, to decide if it’s a past problem, or significant, active, and increasing.
  • Air quality inspections focus on surface molds, and conducive conditions (like excess moisture and inadequate ventilation), rather than structural wood destroying organisms (WDOs), which include wood rot and insects.

Looking for Mold Growth

  • Look in damp locations, especially inside cabinets under sinks, around showers, against basement foundation walls, in the crawl space under the house, and near any dark stains leached out from wet wood.
  • Expect to see mold growth appear after a week damp, as the individual colonies form visible spots the same size, which then merge into fuzzy mats, such as “mildew”.
  • Look for the circular spots that colonies form initially, or the eventual fuzzy mats that form as the spots merge.
  • Wood rot fungus shows as stringy “white rot” (some brown) mats on the surface, which eventually softens the wood, or “brown cubical rot” that breaks into square chunks.
  • Be aware that shadowy black soot deposits on cold surfaces are not mold. They are very thin, greasy, but not spotty, and cannot be bleached out.
  • Note the mold colors: different types often black, or white, olive, green, brown, gray, pink (bathrooms), orange. Many turn brown or black when old.

Sniffing for Mold Odors

  • Use mold odor as evidence of damp growth, pointing to a source or a pathway. But mold odor is only produced when growing by “metabolizing” food (no odor when dry and dormant).
  • Or use odor to decide that it is not mold but something else, like sewer gas, natural gas, damp earth, or dead rodent.Sniffing for mold odor is better than chemical testing for mold VOCs by GCMS, which is slow, expensive, and rarely helpful, because of the many other VOCs that obscure the faint mold VOCs like 1-octen-3-ol.
  • Find the specific area, building material, or air supply where the odor is strongest.
  • Try various tricks to find the source.

Looking for signs of dampness

  • Damp or wet or new materials; water splashing or pooling near the exterior.
  • Moisture condensation on cold surfaces in contact with warm, moist air.
  • Water stains or rust.
  • Mushrooms indicate chronic dampness and possibly rot.
  • Water stained or wavy ceilings or walls below leaks.
  • Water stains with white “efflorescence” salt crystals deposited on masonry.
  • Open suspect wall cavities, etc., by intrusive disassembly.

Find the moisture sources

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

Look in common problem areas

  • Window sills below much condensation on glass or on metal frames.
  • Cold exterior walls, especially behind furniture or in closets.
  • Around tubs, showers, toilets, or roof eaves.
  • Upwind S & W walls near Puget Sound from rain leaks.
  • Downwind N/NE (cooler) side walls and attics near Puget Sound from condensation.
  • Attics, often on large areas under the roof, from condensation.
  • Basements (damp? carpet?), or cabinets below sinks.


  • High humidity indoors that slows evaporation.
  • Inadequate ventilation to dump excess moisture from inside.
  • Inadequate roof drainage: gutters, downspouts, drain fields.
  • Inadequately sloped soil surface drainage away from the building.
  • Inadequate groundwater drainage outside the foundation.
  • Poor drainage within a basement or crawl space (if inadequate drainage outside).
  • Much cellulose debris or bare soil in a crawl space.
  • Exterior siding that traps moisture between wood and impermeable foam insulation.
  • Earth (soil, bushes, moss, landscape materials) in contact with wood structure.



  • Rub a finger across a black surface to see if it’s soot (greasy stain on finger).
  • Wet a small area with bleach to see if the color disappears, like mold does.
  • Look an uncertain area under a magnifier to see if it has any plantlike structures.


  • Disturbing dry mold can release much of it into the breathing air.
  • Remember that glass fibers fill the air in most crawl spaces and attics. So:
  • Wear an air purifying respirator with a HEPA filter cartridge. The best is a powered air purifying respirator (PAPR) supplying air into a helmet & face shield.
  • Wash attic & crawl space inspection clothing often, separately.

NEXT:  3. Mold Decisions

©2004-2019 Richard Knights, Blue Sky Testing LLC
Salem, OR & Seattle, WA,