How to Check for Toxic Mold

Okay, let’s learn to check for toxic mold in your home! Are you excited? No? Oh, okay, got it. Yea, well, I wasn’t into environmental health either… that is, until I got sick from mold in a rental home I lived in. Until I was diagnosed with Chronic Inflammatory Response Syndrome (CIRS), I had never given any thought to checking any building or living space for mold. Since learning what to look for, however, it’s almost like I’ve developed a ninth sense for mold (since we actually have eight senses!), or perhaps a slight obsession. While not a glamorous superpower by any means, I certainly appreciate the health benefits. My hope is that this post can be helpful to you and your health regardless if you’re looking for a new home, checking your current home, or scoping out the Airbnb you booked to help.

Let’s start with a quick review of how mold grows before we cover where and how to check for toxic mold. It needs oxygen, food (which is everything), and moisture. We can’t control oxygen or food, but moisture is the factor we want to avoid. Moisture on wood and drywall creates the perfect conditions for toxic mold to thrive. Some of the places to check might have obvious fungal growth, but many of the places will simply show signs of water damage, indicating a potential mold problem hidden behind the wall, floor, or ceiling. If you’re searching for a new home, depending on the extent of the water damage you find, you can decide if it’s worth it to formally test with an ERMI or walk away. If some of these terms are unfamiliar, visit this post to familiarize yourself with the mold basics.

Without further ado, here are some of the most important places to check for toxic mold:

Outside the home

The House

Check the roof for staining, moss, mold, and algae, as this can be a sign that the roof is rotting.
Check the exterior for vines. While vines certainly have a romantic appeal, they create cracks in the exterior where moisture can seep in.
Check the gutters. Make sure they’re in working condition and that they drain away from the house. A clogged gutter is practically an open invitation for mold!

The Landscaping

Check for trees towering directly over the house since this can lead to falling leaves and branches, along with acorns and gum tree balls, which will constantly clog the gutters.
Check the grading around the home. It is so important for the land around the foundation of the house to slope away from the home so that water will be guided away from the home. Any puddles or soggy ground against the foundation are cause for further investigation. In this post, I share a brief story of what can result from poorly sloped land.
Track any drainage systems. French drains are generally installed when there is a high probability of flooding, so if not done correctly, this could lead to serious water damage.

Inside the Home

In Every Applicable Room

Check for odors. Musty, earthy smells indicate a potential moisture problem. Also, be wary of air fresheners as they’re often used to cover up musty, earthy, mold scents.
Check around windows for staining, sogginess, or recently patched surfaces. The glass of the windows can also be revealing if you see condensation or signs of condensation, indicating a moisture concern. Of course, keep an eye out for mold, too.
Check ceilings and closets for water stains.
Check baseboards. If you see baseboards pulling away from the wall, this is often a sign of water damage.
Look for bubbling, peeling or cracking paint. These are signs that mold is likely growing underneath.
Bubbling, buckling, or dipping of floors. These are indicative of moisture impacting the subfloor, which means further investigation for mold would be wise.

Rooms With Plumbing

Check the caulking, especially in showers. Mold in showers might be common, but that doesn’t make it healthy.
Check under and around appliances. Look behind the fridge, around the dishwasher, and take a gander at the washer hook-ups for mold growth, and signs of mold like staining and sogginess. Look inside the washer and dishwasher, too, as these damp environments are attractive to mold.
Check to make sure drainage works in sinks, showers and tubs. Slow drains can allow water to collect and grow mold.
Check the water heater drain.
Look under all the sinks. Water damage under sinks is so common and not always a huge problem. Take a flashlight and shine it along the wood of any cabinetry to reveal any warping.
Take a peek at the toilet tanks. If there’s a serious mold problem, you can sometimes see mold growing in the tank. This is a tip I learned from Michael Rubino, the Mold Medic.

The Highest and Lowest Levels

Check the attic. Mold grows so easily in the extremities of the house because of their closeness to the elements. Mold in the attic is a sign of poor ventilation and needs to be addressed.
Check the basement or crawlspace. First of all, crawlspaces are not recommended as it is so likely for them to turn into a mold problem since the bottom of the house is exposed to the elements. That’s a recipe for condensation, moisture, and disaster, even when the crawl is encapsulated. Secondly, the lowest part of the home is so important because of the stack effect, which is where the air in the lowest part of the home is pushed through the higher parts. This means that if there’s a problem in the basement or crawlspace, the whole house is impacted. Basements and crawlspaces often house hot water heaters and HVAC units, which are also important to check for signs of mold growth. Mold in the HVAC will be dispersed to every room of the house, unfortunately.

What next?

Okay, whew. We did it! We got through that list! If you’re still with me, you now know how to check for toxic mold, and you’re probably going to go check for toxic mold in your house now. Go ahead; I’ll be here when you get back!

If you just checked your current home and found mold, here are five steps to take. I know firsthand how overwhelming it can feel, and a lot of the information on the internet is inaccurate about mold because it’s not a regulated field.

If you’re searching for a new home, here are 10 powerful things you can do if you’re still exposed to mold, and here are some thoughts on how to find a low-mold home.

Much of what I’ve learned about visually inspecting for mold, I learned from Brian Karr and Michael Rubino. I highly recommend checking out these two invaluable resources and all the free content they share.