Tips for Finding Hidden Mold in a Building

5/1/2017 update, adding ideas from people in the Mold Avoiders group.  🙂 

I wrote this from the perspective of trying to find a new rental or house to purchase. But these might help find hidden mold in a current residence, too. 

Also thanks to my friend D. P. for helping me brainstorm and come up with these.

Besides normal things one would look for (roof damage, signs of water damage on drywall, musty smell, etc.), here are some things to check:

• Ground slanting toward the house (it should slant away for drainage)
• Dense landscaping near house that someone may have watered a lot near foundation
• Downspouts emptying water too close to the foundation. Look for signs of “moss” etc. around/near downspout opening and on the foundation there. It can even affect basements or anything near there inside.
• Even worse, no gutters at all. Amazingly, this can create serious foundation problems.
• Driveways that slant down toward attached garage
• Many trees over house, causing too much shade, wet leaves, etc.
• Mobile homes tend toward mold problems possibly more than stick built, because they may have insufficient insulation, insufficient ventilation, and cheaper materials. If they have been moved, it is possible this has compromised materials causing small leaks, too.
• It may be a good idea to check into the flooding history for the town. Floods can cause major problems in MANY buildings and even in the outdoor air quality.

Maybe the two most important ones???  These mean a very serious, continuing problem.

• Humidity above 60% in any room, area, basement, etc. Humidity should really be preferably below 50%. Any dirt anywhere and paper and other cellulose can start to grow mold around 67%, and you don’t want “pockets” of humidity close to this. You can carry a humidity monitor with you. It should register a new room within 5 minutes. Humidity above that or above 40% in winter usually indicates a hidden leak somewhere or a major construction mistake, especially if the house has been empty for a while (no showers & cooking recently). A moisture meter may be helpful, also, in case there is moisture within a wall that is not affecting room humidity for some reason.
• Condensation in a house anywhere, any season.  This usually indicates too high of humidity, usually due to hidden leaks or construction mistakes causing high humidity. If a basement, it can be “naturally” higher in humidity even without a leak, but if a dehumidifier cannot keep up, THAT usually means a leak. The dehumidifier should be able to keep it below 50% humidity. There should be no condensation on windows unless someone has just taken a shower or it has been extremely cold and the windows are drafty/very cold.

But also, old, dry mold can be a problem.  🙁 

• Ask about prior leaks, which they may not know.
• Under the bathroom and sink cabinets, look for dripping or evidence of someone putting something under the drain, or wrapping with a rag, etc.
• Carefully inspect the corner of patio door windows and windowsills. Mold or water damage can indicate condensation in the wintertime, which is a sign of high humidity from something.
• Check out corners in closets. Humidity can collect here.
• Try to avoid fireplaces, skylights, and ice-makers in fridge if you can.  These all tend to leak. 🙁  
• Avoid crawlspaces unless encapsulated but find out if it had ever NOT been encapsulated. If so, proceed with caution. Check subfloor if you can for any signs of mold, water damage, or discoloration.
• Smell behind dishwasher and clothes washer. Try for a place with no carpet especially in these areas & bathroom.
• Try to avoid tiled showers. They are notorious for getting water through the grout into walls or subfloor.
• Be very careful with a brick-sided house, because brick holds water. Some other sidings do, too, like manufactured stone.
• If caulk ANYWHERE looks bad or old or cracking, imagine water getting behind there. What would happen? If it seems like it could be bad, test humidity, smell, etc. It only takes 48 hours of a hidden material inside being wet before mold can take hold and grow.
• All bathrooms and drier should have vents, with insulated ducts and vented OUTSIDE. If anything is vented in the attic, the attic will have mold. If no vents, the bathroom will have mold.
• If new paint, especially a smaller area, check to see if there are pipes, etc. nearby. Also remember water from roof leaks can travel far and wide, going places I never thought possible. Un-insulated duct-work can also drip water in odd places.
• Check under wall-to-wall carpet for mold in padding or on subfloor.
• Ask to have A/C and then heat turned on WHILE you are there, and smell, etc.
• Run showers for a couple minutes & smell. Humidity in the bathroom can activate mold you might not smell right away.

Christa Upton   Black Hills Picture Books     Edgemont, SD  57735