CMI Basement and Crawl Space Mold Assessment

Question 1

What is the most common moisture source causing mold growth on below-grade basement walls in residential construction?

Accepted Answer

Bulk water intrusion from inadequate exterior waterproofing, grading, and drainage

Answer

Condensation from interior air only

Answer

Plumbing condensation on supply lines in the wall cavity

Answer

Roof drainage routed through interior downspouts

Question 2

When inspecting a vented crawl space with a ground vapor barrier, the inspector finds elevated moisture on wood joists above the barrier. The most likely cause is:

Accepted Answer

Humid outdoor air entering through foundation vents and condensing on the cooler wood structure

Answer

The ground vapor barrier is too thick

Answer

The HVAC supply ductwork above is poorly insulated

Answer

Radon gas migrating through the barrier causing condensation

Question 3

The current best practice for moisture control in crawl spaces per Building Science Corporation and ENERGY STAR is:

Accepted Answer

Encapsulation with a continuous vapor barrier sealed to the foundation walls and controlled mechanical ventilation or conditioned air supply

Answer

Maximum cross ventilation with large foundation vents on all sides

Answer

Covering only 50% of the ground with a 6-mil poly sheet

Answer

Installing a sump pump and leaving the crawl space vented to outdoor air

Question 4

During a crawl space inspection, an inspector observes white fuzzy growth on the bottom of OSB subfloor panels. This is most likely which genus?

Accepted Answer

Penicillium/Aspergillus or Trichoderma species growing on the wood composite binder

Answer

Stachybotrys chartarum

Answer

Serpula lacrymans (dry rot fungus)

Answer

Cladosporium cladosporioides

Question 5

A properly functioning interior perimeter drain system (French drain) in a basement manages water intrusion by:

Accepted Answer

Collecting water that enters the basement at the footing level and routing it to a sump pump for removal

Answer

Preventing all water from entering the basement through the foundation wall

Answer

Applying hydrostatic pressure to seal foundation wall cracks

Answer

Ventilating the basement floor slab to reduce vapor transmission

Question 6

When assessing a finished basement for mold, the inspector should pay particular attention to which location that is most commonly overlooked?

Accepted Answer

The bottom plate and lower sections of framing inside finished walls built directly against the foundation wall

Answer

The top of interior partition walls

Answer

The ceiling drywall adjacent to interior recessed lights

Answer

Electrical panel boxes mounted on interior partition walls