What Mold Needs to Grow
Mold requires four conditions to establish and grow:
- Moisture — the critical limiting factor in buildings
- Oxygen — always present in buildings
- Temperature — 40-100°F (mold can grow in refrigerators to warm attics)
- Food source — organic compounds the mold can digest
Building materials provide the food source. Mold secretes enzymes that break down organic compounds (cellulose, starch, lignin) into nutrients. Materials with more accessible organic content are more susceptible.
Highly Susceptible Materials
🔴 Paper and Paper-Faced Products (Highest Risk)
- Drywall paper facing — extremely susceptible, mold’s preferred food
- Cardboard, books, stored paper products
- Wallpaper (especially vinyl that traps moisture behind it)
- Cellulose insulation — treated but still organic
- Kraft paper facing on insulation batts
🟡 Wood and Wood Products
- Lumber, plywood, OSB — structural framing materials
- Hardwood flooring
- Wood trim, cabinets, and furniture
- Particle board and MDF — adhesives add some resistance
🟡 Fabrics and Soft Materials
- Carpet and carpet padding — especially when wet
- Upholstered furniture
- Curtains, drapes, and bedding
- Clothing and linens stored in humid conditions
More Resistant Materials
🟢 Inorganic Materials
- Concrete, stone, brick, masite — no organic food source
- Tile, glass, glazed ceramics
- Metal (though can corrode and support mold on oxidation)
- Fiberglass insulation batts (unfaced)
- Plastic, vinyl, and synthetic materials
- Closed-cell spray foam insulation
Important: Even “resistant” materials can support mold if dust, debris, or organic films accumulate on surfaces. Mold can grow on the dust layer, not the material itself. This is why mold can appear on glass, metal, and plastic surfaces.
Special Focus: Drywall
Standard drywall is one of the most mold-susceptible materials in modern construction. The paper facing provides an ideal cellulose food source, and the gypsum core absorbs and retains moisture.
| Drywall Type | Mold Resistance | Best Use |
|---|---|---|
| Standard (white) | Low | Dry areas only |
| Green Board | Moderate | Behind tile (not direct water) |
| Paperless (fiberglass face) | High | Bathrooms, basements |
| Cement Board | Highest | Shower surrounds, high-moisture |
Important: “Mold-resistant” means slower colonization, not immunity. No building material is completely mold-proof under sustained moisture. The solution is moisture control, not material selection alone.
Oklahoma-Specific Material Considerations
Pier and Beam Floor Joists
Many Oklahoma homes have wood floor joists exposed to crawl space humidity. Without vapor barriers, these absorb moisture from the ground. TrueSight frequently finds mold on floor joist bottoms and subfloor in these homes.
OSB Sheathing
Oriented strand board (OSB) is common in Oklahoma construction. It’s more moisture-sensitive than plywood and swells when wet. Roof leaks or condensation can cause OSB sheathing to delaminate and grow mold quickly.
Post-Flood Considerations
After Oklahoma flooding events, drywall that was submerged should be removed at least 12-24″ above the water line. Wet carpet padding typically cannot be salvaged and should be discarded.
Research & Citations
- EPA. “Mold Remediation in Schools and Commercial Buildings.” EPA.gov.
- IICRC S520. “Standard for Professional Mold Remediation.” 2021.
- DOE Building America. “Moisture Control and Building Materials.”
- FEMA. “Removing Flood-Damaged Building Materials.”
- Building Science Corporation. “Understanding Mold and Moisture.”