Learning how to test for mold inside walls is crucial if you’re planning to start a new painting project. If you’re repainting your home, you should check for mold in walls as soon as possible – because if you don’t, you may regret it.

The problem with repainting walls that contain mold is that most modern paints act as a sealant – while they help keep moisture out of the rooms that are painted, they have a tendency to allow it to collect behind the walls themselves – and this can spur major growth of dangerous black mold, as well as many other types of of molds.

And if your walls are moldy, new paint isn’t going to cover up their appearance or smell – so you should learn how to test for mold inside walls. If you don’t, you may find your new paint job ruined by creeping, growing mold in less than a month.

So if you’re suspicious and need to know how to test for mold inside walls, read on. We’ll show you how to detect mold inside walls, check for mold in problem areas, and give you tips on how to deal with mold, if you find a problem area.

Moisture Meters & mold testing kits

Moisture Meter

Nutrients, moisture, and time – these are the three required factors for mold growth. Your interior walls provide the nutrients required, but moisture is necessary for the growth of mold. So a great way to find out if you have a mold problem – or at risk – is by buying a moisture meter and a mold test kit.

Moisture meters are generally used by professional mold analysts, and can be a bit expensive for the general public. There are two types – one uses direct contact with a surface to detect moisture levels in the walls, and the other uses radio-frequency signals to detect moisture without direct contact. Both are easy to use, and by testing areas where you suspect you may have moldy growth, you can see if your moisture levels are high enough to encourage mold growth.

Mold testing kits are somewhat different – these are sort of like Petri dishes. You place a small disc with a growth environment that’s conducive to mold near your suspected area. If you are indeed suffering from mold, the spores will spread within 48 hours, and you’ll see moldy growth on the test kit.

If you don’t want to hire a professional, but need to be totally certain about whether or not you have a mold problem, these are great ways to do so – though a mold testing kit is much more inexpensive than a moisture meter.

Discoloration, allergies, musty, smell

You don’t just have to rely on high-tech gadgets to figure out if you’ve got a mold problem. When it comes to how to test for mold inside walls, human sense can be more than enough – if the mold is sufficiently advanced.

If you suspect an area of your home has a mold problem, start by looking for discoloration. Moisture doesn’t play nice with drywall, and even slight moisture collections can leave a telltale imprint.

Smell should be another way you can detect mold. You may not know exactly what your mold problem smells like, but it won’t smell the same as the rest of your house. Sniff around in suspected areas, looking for a tell-tale “musty” odor. Imagine the smell of an old basement or a very old building – are there areas of your home that smell like that, despite showing no signs of moldy growth? That’s a sign that you may have mold growing inside your walls.

Finally, allergies can be a huge indicator of mold growth. If you have a mold allergy and recognize that you’re having the symptoms of an allergic reaction, you have a mold problem in your home – and should get it checked out by a professional, ASAP.

Check air ducts

If you’ve been checking all around your home for mold but aren’t finding it in any of your walls, you may want to check your air ducts. Poorly installed HVAC systems can be breeding grounds for mold spores, as an air conditioner that’s improperly sized for your home can lead to deposits of moisture and other issues that encourage mold growth.

Open up a couple of ducts and shine a flashlight into them. Are they clean? Do you see anything fuzzy or out of place? If you have mold in your vents, it’s not going to stay there for long – the spores will spread through your house to other areas that are dark, moist, and conducive to mold growth.


Borescopes are exactly what they sound like – when it comes to how to test for mold inside walls, they’re the most invasive – but consistent – method used.

These tools consist of a boring tool (bore) and a camera (scope). Using this tool, you bore into your wall in your suspect mold growth area, and use the flexible camera to get an inside look into your walls. This allows you to determine the full extent of your mold problem without tearing down your walls, so it can be very useful when figuring out next steps to deal with mold.

Don’t Try To Remove Mold On Your Own

Removing mold helter-skelter and without a solid containment strategy is a recipe for disaster. Mold spore are extremely durable and robust, and disturbing a mold colony will spread them all throughout your home, potentially making your problem even worse. This is especially important for dangerous black mold and other toxic mold.

So don’t try to remove mold on your own. If you discover that you have an infestation, contact a professional right away. They’ll conduct further testing, and help you come up with a plan to get rid of your mold infestation – permanently.