Attic and crawl space mold, from the moisture source out

Attic mold

Attic mold usually shows up as dark staining on the underside of roof sheathing. Common causes:

• Roof leaks at flashing, vents, and worn shingles, most often noticed during winter storms.
• Bath fans or dryer vents that end in the attic instead of outside, dumping warm, wet air onto cold wood.
• Blocked soffit or ridge venting, often from insulation pushed against the eaves.

Remediation typically means correcting the moisture source and ventilation, then HEPA-vacuuming and cleaning the sheathing and framing, and replacing wet insulation.

Crawl space mold

Many older San Jose neighborhoods have raised-foundation homes over crawl spaces. Signs of trouble include a musty smell in the house, soft or cupping floors, standing water after rain, and condensation on pipes or ducts. Common causes:

• Missing or torn vapor barrier over bare soil.
• Poor grading or gutters that send winter rain toward the foundation. The EPA recommends that the ground slope away from the foundation.
• Plumbing leaks under kitchens and bathrooms.
• Blocked foundation vents that limit airflow.

Remediation usually means fixing drainage and leaks, cleaning joists and subfloor, and installing or replacing the vapor barrier. Some homeowners also ask about crawl space encapsulation or a dehumidifier; ask any company to explain why its recommendation fits your house.