Water Damage & Prevention
Hidden mold: where it grows and how to suspect it
In plain English
A lot of mold grows where you can't see it: behind drywall and wallpaper, on top of ceiling tiles, under carpet pad, in wall cavities around pipes, in AC drain pans and duct liners. The front of a wall can look perfect while the back is covered.
Suspect hidden mold when a space smells musty and you can't find the source, or when there has been water damage and people are reporting symptoms. Vinyl wallpaper and wood paneling are common culprits: they trap moisture against the wall behind them.
Be careful investigating. Opening a wall or peeling wallpaper over growth can release a large burst of spores. If you find hidden mold, the size of the job — and the plan for it — usually grows too.
Key points
- Musty odor with no visible source is the classic sign.
- Back of drywall, top of ceiling tiles, under carpet, pipe chases, AC drain pans, duct liners.
- Vinyl wallpaper and paneling act as vapor barriers.
- Wear protection before opening anything up.
Official text
EPA 402-K-01-001 — Hidden Mold p. 8 Best practice
In some cases, indoor mold growth may not be obvious. It is possible that mold may be growing on hidden surfaces, such as the back side of drywall, wallpaper, or paneling, the top of ceiling tiles, the underside of carpets and pads, etc. Possible locations of hidden mold can include pipe chases and utility tunnels (with leaking or condensing pipes), walls behind furniture (where condensation forms), condensate drain pans inside air handling units, porous thermal or acoustic liners inside ductwork, or roof materials above ceiling tiles (due to roof leaks or insufficient insulation). Some building materials, such as drywall with vinyl wallpaper over it or wood paneling, may act as vapor barriers,[5] trapping moisture underneath their surfaces and thereby providing a moist environment where mold can grow. You may suspect hidden mold if a building smells moldy, but you cannot see the source, or if you know there has been water damage and building occupants are reporting health problems. Investigating hidden mold problems may be difficult and will require caution when the investigation involves disturbing potential sites of mold growth—make sure to use PPE. For example, removal of wallpaper can lead to a massive release of spores from mold growing on the underside of the paper. If you believe that you may have a hidden mold problem, you may want to consider hiring an experienced professional. If you discover hidden mold, you should revise your remediation plan to account for the total area affected by mold growth.
[5] For more information on vapor barriers and building construction, see Resources List. It is important that building materials be able to dry; moisture should not be trapped between two vapor barriers or mold may result.
Photo caption: Hidden Mold Growth
Photo caption: Photo 5: Mold growth behind wallpaper
Citation: EPA 402-K-01-001, Hidden Mold, p. 8.
Read on the official site ↗ See it in the full EPA 402-K-01-001
Citations
- EPA 402-K-01-001, Mold Remediation in Schools and Commercial Buildings — Hidden Mold, p. 8. Best practice Publisher's page ↗