Mold Testing: How to Test for Mold in Your Home

Mold is everywhere but you never want to see it in your house. There are some things you can do to test for mold by doing routine maintenance checks.

What does mold look like

Mold is everywhere. It's a type of fungus that grows from tiny spores that float in the air. It can grow almost anywhere that spores land and find moisture and a comfortable temperature, between 40 and 100 degrees F. Typically that includes about every damp place in your home. You can easily spot the most visible type of mold, called mildew, which begins as tiny, usually black spots but often grows into larger colonies. It's one of the easier ways of how to tell if you have mold. It's the black stuff you see in the grout lines in your shower, on damp walls, and outdoors on the surfaces of deck boards and painted siding, especially in damp and shady areas. A mildewed surface is often difficult to distinguish from a dirty one. To test for mold and mildew and how to tell if your house has mold, simply dab a few drops of household bleach on the blackened area. If it lightens after one to two minutes, you have mildew. If the area remains dark, you probably have dirt.

Is it Mold or Dirt?

Most mold is unmistakable, but sometimes small or largely hidden growths just make a surface look dirty. A quick test for mold can be done when you dip a swab in diluted bleach (1 part bleach, 16 parts water) and dab it on the wall. If the spot quickly lightens (or keeps coming back after cleaning), assume it's mold. Mold testing kits are available that detect the presence and identify the type of mold, but they won't help determine the cause or what to do about it.

Probe the Area with a Screwdriver

Mildew is a surface type of mold that won't damage your home's structure. But other types of mold cause rot. If you want to know how to find mold in your house, probe the suspect area with a screwdriver or other sharp tool as a test for mold. If the wood is soft or crumbles, the fungi have taken hold and rot has begun.

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Probe the Area with a ScrewdriverFAMILY HANDYMAN

Probe the Area with a Screwdriver

Mildew is a surface type of mold that won't damage your home's structure. But other types of mold cause rot. If you want to know how to find mold in your house, probe the suspect area with a screwdriver or other sharp tool as a test for mold. If the wood is soft or crumbles, the fungi have taken hold and rot has begun.

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Check for Plumbing Leaks

Check for Plumbing Leaks

If you see mold near water pipes, waste lines, icemaker lines or plumbing fixtures, chances are the mold is feeding off a nearby leak. Let the water run while you check the pipes and surrounding area for damp spots to see if there's mold from water leaking. Remember that water can travel in any direction—down, sideways or even up when it wicks into absorbent material like drywall—so the actual leak may be some distance from the mold. Once the leak is found, fix it. This portable work light is perfect for scoping out problems inside cabinets and other hard-to-reach spaces. Learn how to clean black spots in the bathroom here. Is is safe to clean with bleach in the bathroom? Get the answer here.

Look for Outside Leaks

If mold is growing on an exterior wall or ceiling, first look for a leak in the wall or roof as a test for mold. Measure from the moldy area to a reference point like a door, then find the spot on the other side of the wall or ceiling. Closely inspect nearby vents, roof flashing, decks, window wells and anywhere wood is rotting. Look for ground sloping toward the house and downspouts emptying next to the wall. If the ground around the house gets too wet, moisture will wick into the foundation or slab and become persistent dampness. Make sure you properly install flashing when you're fixing the leak.