Moisture, Water and Mold Problems in a House
Indoor moisture problems follow one of three paths: liquid water entering from outside, water vapor produced inside, or warm humid air condensing on a cold surface. The EPA puts the target indoor relative humidity at 30–50%; sustained readings above 60% support mold growth on drywall paper, dust and wood within 24–48 hours of wetting.
Basement moisture
Seepage, damp walls, floods after rain.
Crawl-space moisture
Standing water, wet insulation, ground vapor.
Mold
Visible growth on walls, ceilings, closets and framing.
Condensation
Sweating windows, walls, ducts and pipes.
Indoor humidity
Whole-house humidity that is too high or too low.
Water intrusion
Leaks entering through walls, floors and slabs.
More moisture, water & mold problems
Moisture, Water & Mold questions homeowners ask
What indoor humidity is safe?
The EPA recommends keeping indoor relative humidity between 30% and 50%, and never above 60%. A $12 hygrometer placed away from vents gives you the number you need.
Does mold always mean I need remediation?
The EPA guideline is that areas under 10 square feet can normally be cleaned by the homeowner with detergent and water. Larger areas, HVAC contamination or sewage-contaminated water call for a remediation contractor.