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Black Mold On White Walls

How To Detect Mold Inside Walls

You keep everything you can see in your home clean and sanitized, but have you considered what lurks beyond your line of sight? Your walls can house dangerous black mold growth even if you clean regularly.

Water damage can create a prime environment within walls for mold and mildew to fester.

Learn how to spot this hidden intrusion, keep it away for the long term, and prevent it from coming back.

What Causes Mold To Grow Inside Walls?

There are a few common reasons mold will grow inside walls that even attentive homeowners could miss out on.

A broken water pipe between walls allows water to pool and paves the way for mold growth. Even if you dried all the surface water, porous building materials will soak up the water and create a damp space for fungus.

A window leak also can lead to water exposure in between walls. A small hole will lead to a persistent leak letting water flow down the inside of your wall.
Humidity can creep into every available area of your home and take root. Inadequate ventilation will cause mildew to build up in all areas that are not sufficiently air-conditioned. People who live in hot and wet climates are most at risk of humid air causing mildew growth.

Poor insulation and siding are some of the most common reasons mold can grow within walls. When insulation becomes wet, it stops acting as a barrier and becomes completely porous. This is a typical chain of events: the roof has a small hole that leaks on the insulation, allowing water to pool inside the skeleton of your home, making the ideal conditions for mold.

Read more: Is there mold on basement walls?

Is Mold Inside Walls Dangerous?

In as little as 24 hours, mold can begin to grow in damp and dark areas. The dreaded Stachybotrys chartarum, or black mold, feeds off cellulose, which both wood and drywall are made of. Oxygen, water, food, and darkness are all that’s needed to make this take root. It is both easier and faster for mold to grow than you may think.

Black mold can cause hay fever symptoms in healthy people and lead to severe respiratory problems in people with preexisting conditions. Studies have shown black mold can cause sleep apnea, hives, rashes, and other common allergy symptoms.

Along with the sickness this fungus can bring, the structural integrity of your walls is threatened by mildew. Since mold eats cellulose, it slowly takes apart the building blocks of your home and puts it at risk of collapse.

Mold inside walls is very dangerous because it is so hidden. The spores hidden in crevices can be carried away by the air current of an HVAC system to infect all areas of your home.

Read more: How to tell if mold is toxic?

Black And Green Mold On White External Wall

How To Detect Mold Inside Walls

Keep all of your senses keen to pinpoint the location of the fungus.


Mold produces a unique musty smell that permeates out from its location. Sniff for a deep earthy smell like the forest floor. Get close to outlets and other holes to locate the source precisely.


Water damage and mold growth often go hand in hand. Look for signs of water damage along your walls. Any discoloration from brown to yellow to black is a serious warning sign.
Any slimy or fuzzy growths appearing is a sure-fire sign of a colony within your walls. Any color from yellow to green to purple to red to black is a bad sign.


If you notice condensation on your walls or they feel wet to the touch, immediately get help. Do your best to dry any surface water; you can attempt to clean faster than mildew can grow.

Peeling and cracking

Wallpaper and paint should never peel or crack. Bulges and bubbles are a sign of excess moisture slowly building up over time. If you see your walls warping or twisting, you have water damage and will need to bring in an expert to properly dry and prevent a mold infestation.

Read more: Can a water leak be the cause of mold?

How To Remove Mold Behind Walls

The most challenging part of cleaning behind a wall is that you will have to tear it down in order to access the affected areas. It is best to work with professionals to avoid cutting through any electrical wiring or plumbing piping.

Should you manage to access the interior yourself, follow the same steps to remove mold from wood flooring. Create a cleaning solution of bleach and water and work in the mixture until you lift the mold completely and you cannot see any remnants.

Lastly, you must fully dry the area. Start with a cloth to remove surface water, then run a dehumidifier for at least 24 hours so that the site will dry all the way through.

Frequently Asked Questions

Is Mold Inside Walls Dangerous for Babies?

Prolonged exposure to any form of mold or damp can result in varying respiratory illnesses, including reduced lung function.

Can Mold Inside Walls Make You Sick?

Yes. Whenever you discover signs of mold, you should act promptly to remove them, as they aren’t just unsightly. They can be deeply harmful.

Is Mold in Walls Covered by Homeowner’s Insurance?

In most cases, yes, your homeowner’s insurance should cover you. Always double-check the specific details of your policy!

Will Mold Die if it Dries Out?

No. Drying out is not enough to kill mold entirely. However, it will significantly stunt its growth.

Can You Live in a House with Mold Inside Walls?

Yes, though it isn’t exactly recommended. You should look to remove any signs of mold as soon as possible to minimize damage.


Mold inside your walls is nothing to take lightly. This project is generally above your typical DIY capabilities.

Luckily, All Dry USA is here to save the day. With ten years of mold remediation and removal experience, we can get it out of your walls and make sure it won’t come back.

Plus, we don’t just handle the mold; we can tackle any associated water damage as well. Trust the experts to quell your infestation and get your home back in tip-top condition.

Call (888) 998-2379 or request a free online quote today!

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