CMI CMI Building Materials & Construction Systems

Question 1

Why is gypsum wallboard (drywall) considered a high-risk material for mold growth in water-damaged buildings?

Accepted Answer

The paper facing and gypsum core absorb water readily and provide a nutrient source for mold

Answer

Drywall contains antimicrobial additives that fail after 5 years

Answer

Gypsum board only supports mold growth if it contains recycled content

Answer

Only the painted surface of drywall is susceptible to mold, not the core

Question 2

At what moisture content (MC%) does wood framing typically become susceptible to mold and decay fungus growth?

Accepted Answer

Above 19% moisture content

Answer

Above 8% moisture content

Answer

Above 30% moisture content

Answer

Wood framing is not susceptible to mold at any moisture content

Question 3

Which type of insulation is most resistant to mold growth due to its non-organic composition?

Accepted Answer

Closed-cell spray polyurethane foam (SPF)

Answer

Cellulose insulation

Answer

Fiberglass batt insulation

Answer

Cotton batt insulation

Question 4

A mold inspector finds mold growth behind vinyl wallcovering in a hotel corridor. What building science principle explains this common problem?

Accepted Answer

Vinyl acts as a vapor barrier trapping moisture between the wall and the covering, creating hidden mold growth

Answer

Vinyl wallcovering is a food source for mold species

Answer

The adhesive used under vinyl wallcovering introduces moisture into the wall

Answer

This only occurs when the HVAC system is set too cold

Question 5

What makes oriented strand board (OSB) sheathing more susceptible to mold than traditional plywood in similar conditions?

Accepted Answer

OSB's higher moisture absorption rate and longer drying time compared to plywood

Answer

OSB contains more wood preservatives that attract mold

Answer

Plywood has a porous surface that dries faster than the smoother OSB face

Answer

OSB and plywood have identical mold resistance properties

Question 6

Which concrete or masonry characteristic makes it susceptible to mold growth despite being an inorganic material?

Accepted Answer

Dust and organic debris accumulate on porous masonry surfaces, providing nutrients for mold to grow

Answer

Masonry contains organic lime that mold can metabolize directly

Answer

Concrete emits water vapor that directly feeds mold colonies

Answer

Mold cannot grow on concrete under any circumstances