Building Materials & Mold Growth Flashcards

A remediator finds white efflorescence and mold on a basement concrete wall. What does this combination most likely indicate?

Answer: Active moisture migration through the wall driving salts and supporting mold

Efflorescence is caused by water carrying soluble salts through concrete to the surface; this same moisture pathway also provides water to support mold growth on organic material at the surface.

What is the term for mold that grows primarily on the surface of a material without penetrating into the substrate?

Answer: Superficial (surface) colonization

Superficial colonization describes mold that grows on the material surface using deposited dust and organic debris as nutrients without penetrating the substrate, which is more common on inorganic materials.

Which of the following building assemblies poses the HIGHEST mold risk in a hot-humid climate (Climate Zone 1-2)?

Answer: Vapor-retarder-painted interior drywall with fiberglass batt cavity insulation

In hot-humid climates, a vapor retarder on the interior can trap outward-driven moisture from the hot exterior, allowing condensation in the wall cavity and promoting mold in the fiberglass and on sheathing.

What is the purpose of a 'mold-resistant' drywall product (such as purple board) in construction?

Answer: To provide a substrate that resists mold growth if intermittently exposed to moisture

Mold-resistant drywall uses fiberglass mat facing and additives to slow mold colonization during temporary moisture exposure, but it is not a substitute for moisture control and will still support growth under sustained wet conditions.

What happens to wood's structural integrity when mold transitions to wood-decay fungal activity?

Answer: Cellulose and lignin degradation reduces load-bearing capacity

Wood-decay fungi enzymatically break down cellulose and/or lignin—the structural components of wood—causing loss of strength, stiffness, and load-carrying capacity.

A remediation crew is removing moldy fiberglass batt insulation from a wall cavity. What is the MOST important PPE consideration beyond N95 respirators?

Answer: Full-face PAPR due to combined mold spore and fiberglass fiber exposure

Disturbing moldy fiberglass insulation releases both mold spores and fine glass fibers simultaneously; a PAPR with appropriate cartridges provides superior protection against this combined respiratory hazard.

Which factor explains why mold grows faster on new construction lumber than on older, well-dried lumber in similar humidity conditions?

Answer: New lumber contains more readily available nutrients and higher initial moisture content

Green or freshly milled lumber has higher moisture content and abundant accessible carbohydrates and nutrients that have not yet been depleted by weathering, making it a richer substrate for rapid mold colonization.