Person holding magnifying glass over a house

Most of us have been there. You discover some gross ooze under your sink, or you catch a whiff of something not so fresh in the basement. Most of the time, it’s nothing to worry about, but these signs could lead to something hugely problematic if not adequately addressed: mold.

Mold can usually be addressed by homeowners themselves, but occasionally, it can take hold and cause major headaches — both literally and figuratively. Problematic mold can cost thousands to remediate and cause untold disruption to your life, not to mention the health problems mold might cause.

To help you better understand if you’ve got a problem brewing, we’re going to detail seven signs that you’ve got mold in your home. The first one might be obvious, but trust us, there’s more than meets the eye.

#1: You See It

It might seem like a no-brainer, but seeing a little bit of mold can be an indication that you’ve got a major infestation on your hands. Keep in mind that mold often grows where you can’t see it, so those little black spots on the crown molding might be revealing a much bigger problem in your ceiling.1

Pro Tip: Not all molds are created equal, and some are more dangerous than others. Learn more in our guide to the most common types of household mold.

Mold can grow wherever moisture and organic matter are present. That means it can hide behind your wallpaper, underneath your carpet, in your attic’s insulation, or in that stack of books you keep by your bedside table.

We’re not saying this to make you feel paranoid that mold is all around you — though technically it is,2 but it’s not a problem most of the time. We’re saying it to make you aware that if you spot mold in your home, there’s a good chance it’s also in places you might not be able to see. But you might detect it with another sense.

#2: You Smell It

We all know that thick, musty odor you smell when entering a damp crawlspace or basement. You guessed it: That’s caused by mold. You see, when mold grows and reproduces, it gives off compounds called microbial volatile organic compounds, or mVOCs for short. These often produce strong smells, and while the science behind it is still a little iffy, there’s evidence these compounds can cause symptoms including headaches, dizziness, and nausea.3

FYI: There was a big scare about a decade ago about “toxic mold syndrome” and the dreaded black mold — most of which was overblown. While extensive mold contamination can cause negative health outcomes, there is next to no evidence that mold can be extremely dangerous or fatal for otherwise healthy individuals.

We’re not saying you need to go around sniffing every surface in your house, but if you catch a whiff of something unpleasant, you probably shouldn’t ignore it. You also shouldn’t ignore household damage that involves water. That can cause big problems in the long run.

#3: You’ve Had Water Damage

Moving away from our human senses for a minute, another sign you have mold is if you’ve had a water damage incident. Let’s say your toilet lid had a hairline fracture in it that leaked water onto your bathroom floor for days while you were out of town. You come back to a soggy, squishy floor. You turn off the water, get the toilet fixed, and think the problem is solved.

Wrong. You could have mold growing under your bathtub and underneath the floorboards, and since the bathroom is located upstairs, your bathtub could be threatening to crash through your living room ceiling.

Don’t ask us how we know.

If you’ve had any household damage that involved water, you need to dry the area out completely. Dry up as much of the water as possible, clean the surface, and consider running a dehumidifier in the area for a few days. Yes, a few days.4 You might also consider purchasing a moisture testing kit.

#4: You Have Warped Walls or Cracked Ceilings

Another type of household damage that might indicate you have a mold problem is if you’re noticing cracks in your ceiling or bulges and warping in your walls.5 Like we said above, mold feeds on organic material and can grow in places in your home you can’t see. If you’re noticing warping or cracking, that can indicate mold is eating your drywall or the structural elements behind it.

If you notice these physical signs that something might be wrong, do not simply address them cosmetically. There’s a reason why your ceiling is cracking, so don’t just slap a layer of joint compound on it and call it a day. For big problems like these, you’ll want to call in a professional.

Pro Tip: If you’ve read this far and what we’re saying is checking boxes, you might consider performing a mold test in your home or calling a mold inspector.

Sometimes, though, the indication your home has mold will have nothing to do with the physical structure itself. Sometimes your own body might be telling you something’s wrong.

#5: You’re Experiencing Physical Symptoms

Most children have a head cold or sinus congestion from time to time — most parents do too for that matter —- but when these ailments are chronic or recurring, you might consider that something could be wrong in your physical environment.6 It might be mold if you or your child has a persistent:

  • Headache
  • Cough
  • Sore throat
  • Runny nose

This includes any other unexplained maladies, like dry, scaly skin. That said, it’s going to be pretty difficult to isolate the cause of mysterious physical symptoms, especially when you’re talking about mold. The impacts of having mold in our domestic and professional spaces are not well understood, but the science is clear that mold can cause allergic reactions. How those manifest is up for debate, but if you’ve exhausted other causes, mold might be the culprit.

Pro Tip: If you’re concerned about the impact household mold might be having on your little ones, read our guide to the dangers of mold for babies and toddlers. There’s a lot of misinformation out there that we set straight.

Another culprit? Moisture. Moisture is mold’s favorite thing, and if your home has high levels of it, you should almost expect mold to show up.

#6: You Have High Humidity

Mold and moisture go hand in hand. Where one exists, you’ll almost always find the other. What does that mean for your family, though? If you’re concerned with mold, you’re going to want to keep the relative humidity in your house down to a reasonable level.

What do we mean by that? Well, the EPA recommends indoor relative humidity should be kept below 60 percent — ideally between 30 and 50 percent.7

Pro Tip: Want to know more about mold, your family, and your home? We’ve compiled a complete guide on everything you need to know about mold.

A lot of the time, this can be accomplished by using your air conditioner and heating system wisely, but it can be difficult in some climates. One of the best things you can do to shield your family from mold exposure is to purchase a dehumidifier and place it in mold-prone areas of your home — especially ones below ground level, such as basements and crawl spaces.8

Now, you can try your best to keep moisture out of your home, but sometimes Mother Nature has other plans.

# 7: You’ve Gone Through a Major Weather Event

Hurricanes and floods are major causes of widespread mold outbreaks, and remediation is usually needed if your home has been impacted.9 The CDC says people with a weakened immune system should be especially cautious after a major event like this, as mold levels in the entire area might be unsafe.

Pro Tip: If you’ve experienced widespread flooding from a natural disaster, it’s unlikely that your homeowners insurance will cover the costs of mold remediation or the damage it caused. Read more on this in our guide to mold insurance.

Luckily, most of us will never have to live through the horror of a natural disaster, but smaller weather events can also present major problems. Particularly strong rainstorms can test the limits of our windows’ weatherproofing and big windstorms can compromise the integrity of our roofs. You don’t need to fully inspect your home from top to bottom every time the sky goes gray, but be aware that the weather doesn’t always stay outside.

Now that we’ve talked about the signs your home might have mold in it, let’s talk about what you should do if it does.

What to Do If Your Home Has Mold

First off, don’t panic. Even if you find mold contamination, it’s not necessarily dangerous to you or your family. You need to take some precautions if you have young children, elderly folks, or immunocompromised individuals in your home, but for otherwise healthy adults, short-term exposure to relatively small amounts of mold is no big deal.

Depending on where the mold is located, it might be pretty simple to clean. It might be as easy as using disinfecting spray and a rag, or you might have to get a little more serious. It all depends on where the mold is and how capable you are of cleaning it yourself. Regardless, though, you should always wear the proper protective gear, including:

  • Eye protection
  • Long sleeves and pants
  • Gloves
  • Closed-toe shoes

Ultimately, you just want to limit your exposure to the mold. Get rid of anything that has been contaminated, such as cardboard boxes or clothing, and make sure you dry out the area completely so the mold doesn’t come back.

If the mold contamination is extensive — the EPA defines that as anything over 10 square feet — you should call in professional mold remediators. If that sounds like a daunting task, don’t worry. We’ve written a whole guide on vetting mold remediation services to make the process as easy as possible.

Mold Signs FAQs

Where does mold typically grow in a home?

Mold likes to grow in warm, dark, moist places. Think bathrooms, crawlspaces, basements, and under sinks.

Can I clean mold myself?

Most of the time, mold contamination doesn’t require professional remediation. If the infestation is significant, though, you might need remediation.

How much does mold remediation cost?

Mold remediation costs depend entirely on the extent of the contamination, but a good rule of thumb is to expect to pay between $10 and $30 per square foot. That said, if your whole home is contaminated, you might have to pay tens of thousands of dollars to have it restored.

Is mold dangerous?

Most mold contaminations pose no threat to healthy adults, but be cautious if you have young children, elderly people, or those with health conditions in the house.

Can mold affect my pets?

Mold can be even more dangerous for our animals than it is for us. Because their bodies are much smaller, they can’t tolerate exposure for as long as humans can.