Can There Be Hidden Mold in my House?

I get at least a few phone calls per month, where the person tells me, they are sure they have hidden mold in their home. Particularly inside their walls. Why are they so sure of this?

Because they’re mysteriously sick all the time. When they are away from the house for a period of a few days, they feel much better. Come home, sick again. They have convinced themselves it must be hidden mold inside walls of their home, because there is no visible mold in the house.

So, is it possible for mold to be hidden in the walls of a house without any other signs of visible mold. The simple answer is, yes. It is possible. But it is not very likely.

Can There Be Hidden Mold in my House PIN2First, before I delve more into the why’s and why nots of this, let me talk a little more about these frequent calls I get that I mentioned above. Some of these people could be hypochondriacs. But more of them, I think, really do feel sick at home. Yet, in reality, it could be so many other things causing them to feel bad. It just seems that “toxic mold” gets the blame over other possible causes, by default.

Other possibilities: Lead poisoning, asbestos, cigarette smoke, radon, unhealthy, filthy conditions from many pets in the house (pet urine in carpets, etc). I could go on and on. It does not have to be mold. Do me a favor, if a mold professional comes to your home and does an inspection and even does air sample testing and tells you, you have no mold issues, believe him and move on. Cross mold off your list and check other reasons your home could be making you sick. Yes, I occasionally get someone who will not believe me when I tell them that they have no mold issues in their house. Ok, I’m done with that rant. Back to the subject at hand.

As I said earlier, it is possible for mold to be hidden inside walls, but not likely. Here’s why: Mold needs moisture to start growing. Inside most walls, it is dry, so mold will not just suddenly start growing there. Even if you intentionally planted some black mold spores inside a wall and close it up, mold will not grow. It needs moisture.

I know what you are thinking – What about a basement wall? If a drywall wall is built over the foundation wall, as is the case with most finished basements, then, the foundation leaks, you are going to have mold growing inside that wall. This is true. But if a foundation is leaking, it will become evident very soon from visible signs on the outside of the wall that there is a leak. Mold may grow hidden inside the wall in this case, for a short period of time before the mold is also growing on the outside of the wall and is visible to anyone entering the room where the foundation is leaking. So, technically, in this scenario, yes, the mold will grow hidden inside the wall first, but in just a day or so, there is mold on the inside and outside of the wall.

Bottom line, if you have no moisture issues anywhere in your house, I think you can safely conclude, there is no hidden mold growing inside the walls. But, very often, there can be hidden mold in your house. Not hidden in the walls, but hidden from your view. I find this all the time when I am doing mold inspections. Homeowners may not think they have visible mold, but a closer look can reveal they do have visible mold, once furniture is moved or when looking in a place not ordinarily seen by our eyes. Some examples are pictured below.


Hidden Mold Behind Appliances and Cabinets

Can There Be Hidden Mold in my House?
Hidden mold behind appliances and kitchen cabinets:

This previous customer had no idea he had mold until he moved his stove to clean behind it.

The refrigerator line (seen in picture) had been leaking for months.

The kitchen cabinets had to be removed and the moldy walls behind the cabinets had to be remediated and replaced. The cabinets had to be completely remediated.

(More on this situation in my next blog)





Find Mold in Attic

Find Mold in Attic
Hidden Mold in the Attic:

This homeowner never knew she had mold in her attic until she wanted to sell her house and a home inspector pointed it out.

This particular attic had very extensive move.

It was hidden mold in her house because she had no idea. Come on, when was the last time you looked around in your attic?









Hidden Mold Behind Furniture

Hidden Mold House
Hidden Mold Behind Furniture:

This older couple never knew mold was on their basement walls, until I pulled all the furniture and boxes away from the walls.

When was the last time you moved some of your heavy furniture away from the walls, particularly in your basement?

Problems can be not so hidden, if you move furniture regularly, well, at least once a year.







Mold Hidden in Home Closets
Mold Hidden in Home Closets


Hidden Mold in Closets:
Closets are a very common area for mold to be hidden.

If a closet is filled with storage containers or boxes, one could not realize a serious mold issue could exist.

Another area I commonly find mold is closet ceilings. When was the last time you looked at a closet ceiling?



Hidden Mold on Basement Ceilings and Crawl Spaces


Hidden Mold on Basement Ceilings and Crawl Spaces:

No explanation needed.

We don’t normally examine these areas, yet they are the single most common areas of mold contamination in houses old and new.

So, yes, you can have hidden (from your line of sight) mold in your home. But even in these
situations, moisture must be present for mold growth to occur. If you are certain you have a dry basement or crawl space and you have no plumbing or roof leaks, you can be certain, you do not have any mold issues. You can breath easy knowing that.

In my next blog, I will share an experience of a job I had where mold was hidden in the wall and behind kitchen cabinets, unknown to the homeowner, and it was a bad situation that you will want to make sure never happens to you.

“Marvin the Mold Guy”

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One Response to “Can There Be Hidden Mold in my House?”

  1. Marc says:

    Your post was very helpful. My mother was very concerned whether there was mold hiding in her house. Using the tips you gave we did find a hidden area under the house that could be mold. As a result, we ordered a mold test as you suggest. Thanks so much for the helpful information!

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