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How to Check for Mold in Your House

Mold in your house

You might think that most mold in a house is visible. While this is true, there are two points to consider:

First, there are places you haven’t thought to check for mold in your house where it may exist

Secondly, you have to think ‘there may be the presence of mold in my house where I’ll never see’ such as all around you in the air.

If you’re searching for how to check for mold and want to find out what type of mold you have inside you house, then read on.

We’ll cover all the places to first check for, then the proper way to test the mold you find in your home.

Is Mold in Your House Dangerous?

Before we get to the checking and testing, let’s first understand possible health effects of mold around us.

Most house molds and their spores are allergens, meaning they cause allergic reactions in people sensitive to indoor mold.

The so-called “toxic molds” have been blamed for even more serious health conditions such as memory loss, fatigue, seizures and brain damage. These are extreme, of course,

Children growing up where large amounts of mold is indoors, namely schools and homes, have more frequent asthma attacks and higher incidences of wheezing and upper respiratory infections.

Even for normal people, reactions range from increased runny nose, eye irritation, or congestion. 

Children (and many adults) spend most of their time at home, so it’s a no-brainer to learn how to check for mold in your house and find out what type of mold is there.

Before getting too worried though, it’s important to understand that some mold is present in any house.

Since it is a natural organism that feeds off of organic materials and thrives when any moisture is available, mold in a house is unavoidable.

Where house molds are a problem is when there is excessive and persistent moisture for it to live on and reproduce.

The Process for Checking and Testing Mold

Checking and testing for house molds begins with identifying places indoors where moisture may exist more than you want.

Once you find mold; if you’re concerned, move on to a mold test to find out what you’ve got and if it’s harmful.

In all cases, always eliminate any water problems.

Ok, here’s where to check for mold indoors (some you might not have thought of):

Where to Check for Mold in Your House

Investigate duct work

Check your HVAC system, mainly duct work. Moisture can get into your ducts in high humidity or in cases of condensation.

Over time, leaky duct joints, especially non-insulated ones, can bring regular moisture into placed like attics.

This could create a moist environment for mildew. Check for mold in basements, attics, crawlspaces; wherever ductwork runs and especially where it is joined together.

Look anywhere water can leak

In places where appliances might leak or overflow can pose a mold threat.

For example, when a washing machine overflows, a water heater leaks or hoses burst and no flood drain is nearby, water may seem to “dry up”. But, actually it soaks into carpet, floorboards and drywall.

Mold in the house often lives in these places if there are regular leaks.

Mold in the bathrooms?

Mold in a home bathroom

Poorly ventilation can definitely lead to unwanted bathroom mildew and even mold.

We’ve all seen the surface mold growing in the tub, shower walls or on the ceilings above showers or sinks. This may look common, but it’s still mold living in your house!

Check on the wall inside the cabinet under the sink and also behind toilets and on shower curtains.

Consider inside the walls

In warm, moist environments, impermeable vinyl wall covering can trap most air inside walls as the air moves from the warm outdoors to the cool interior.

This degrades the drywall and the adhesive behind the wall covering.

This is hard to check unless you remove the wall covering. If you can, replace with permeable material to allow these areas to dry.

On drywall itself

Moldy walls can occur, especially when wall board is used as a tile backer.

It quickly degrades when subjected to moisture; house mold speeds this process up. Cement board is a better alternative if possible. Ideally, a layer of concrete on the walls should be your top choice.

Mold in crawlspace?

In crawl spaces where bare earth floors transmit large amounts of moisture constantly, you’ll usually smell something funny.

You’ll most likely detect a musty odor here, so sample this air when doing an interior mold test.

Check under the fridge

In the condensation pan under the coils of your refrigerator can harbor molds. A pan is there for a reason, to catch the dripping condensation.

Stay on top of this, emptying the pan if necessary and keeping the pan clean by adding a few drops of bleach whenever you think about it.

Mold in basements

Check around finished concrete basements that are not adequately waterproofed from the outside.

These areas can allow moisture to penetrate and become trapped behind vapor barriers, carpet, insulation and drywall. This is a huge source and place to check for mold in your house that you might not have imagined would be there.

Always conduct a moisture test before finishing a basement like this.

Check for mold around windows

On improperly flashed or caulked windows and doors you might find large amounts of window condensation in the winter time.

Check all around framework to locate possible water infiltration. If you suspect problems, remove flashing to inspect for mold.

Mold from leaky roofs

Leaky roofs, especially poorly flashed areas, allow rain to infiltrate attics, insulation, eaves and other difficult to inspect areas.

If you have a roof that has leaked after multiple rains over time, it’s important to check for mold in effected areas.

How to Check the Type of Mold in Your House

Of course you can use a variety of remedies to try and clean up any mold you find but in a lot of cases it’s good to find out more.

One the best ways you can start the process of finding out what kind of mold lives in your house is through a self mold test kit.

Here’s how it works:

1. Pick up at Least Two DIY Mold Test Kits 

One of the most highly rated is made by Mold Inspection Network  – You can pick one up here for a little less money than what Home Depot or Lowes sells test kits for.

It comes with three surface testers. This is usually enough, but they can quickly be used up say if you’re testing your bathroom, kitchen, the air inside your home and the air outside your home.

If you can swing it, pick up two of these mold testers and you’ll be able to do a complete check of your immediate living environment. Trust me, this lets you rest easier.

DIY Mold Test Kit

2. Collect Mold Samples from Your House

Follow the directions on the package. The little plates will remind you of biology class back in school – it’s kind of fun you get to use them for a “real life” test now as an adult.

These are actually quite easy to use and allow you to instantly capture mold from surfaces where you see mold.

Collect mold in your house

3. Mail Your Mold Samples

After collecting mold in your house, the process is pretty easy from there.

You simply package up the collectors and ship them to the included address.

You’ll include your contact information so you can get your analysis and results back quickly.

4. Receive Your Mold Report

Mold test result from home

Example of a mold test report

Usually well within a week, you’ll get a report emailed to you showing the results of the mold test.

Just to set expectations, you may not actually understand what the analysis means unless you work in a biological lab!

It’s ok though… you can email them back with any specific questions and usually get a quick reply.

The company will often suggest giving them a call, and you can speak with a knowledge technician. It’s essentially a helpful consultation that goes over your report and spells everything out for you.

This consultation is 100% included in the price of your test kit and includes the good AND the bad, should there be any concerning information.

The point is you will know, and nothing beats actually speaking with an informed expert so you can become an informed homeowner and know exactly what you’s going on with the mold in your house.

Another Mold Test Kit Product

Another popular mold test kit is from Pro-Lab. Their system uses a petri dish to “capture” air-borne mold.

In that kid you just pour a small vile of liquid into the petri dish, then let the dish sit out with the lid off for an hour.

After an hour, put the lid back on and wait for whatever mold it captured to incubate for at least 48 hours.

If mold has grown in there (which it most likely will), you have the option of sending the petri dish into Pro-Lab.

They provide the envelop and postage! A couple weeks later, they send you a report from their analysis of the mold growth in your house.

For the DIY Mold test

Some Points about Testing Your House Molds

Since molds live around us all the time (inside and out), your mold testing is more than likely going to pick up spores–plan on seeing growth in your petri dish. (see photo)

Mold in home's air

Get two mold test kits 

Since mold is going to be present, it’s important to see what’s going on outside AND inside.

You want to find out if you have something growing indoors that’s different from outdoors.

You do this by sampling the air both outdoors and indoors.

DIY mold testing in summary

Mold growing around house




Test kits like the ones mentioned above allow you to do both air sampling (sitting out in open space such as your living room or directly in front of a air vent for testing duct work).

They also allow you to scrape off some living mold on a surface using a Q-tip and placing it in a petri dish to grow or directly on a slide.

Both kinds can have an analysis done to determine if the mold in your house is toxic.

The report you get back will give you detailed names of the house mold identified in your samples.

While explanations may tell you all the different types, be prepared that it can also conclude that you may have an abundance of moisture in your house, i.e. if more growth occurred in a sample dish that was used inside.

Not only will you be surprised by how much mold growth appears in your dish after 48-72 hours, you may also see a variety of colors (black mold, orange mold, green mold, fuzzy gray mold and more).

Don’t be too alarmed though as even the strangest kinds will be common and harmless to most people in low quantities.

When Should I Check My House for Mold?

It is recommended to check for house mold if you:

  • See growth somewhere in your house
  • Smell musty or or mildewy odors
  • Have a situation where you or someone shows signs up allergies indoors
  • Suspect regularly occurring moisture somewhere in your house.

View an actual mold in house report to see what comes back after you analyze your house mold.

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