Mold in Attic - What Caused It and How to Remove It

When was the last time you stepped into your attic? 

Can’t remember? That’s what we thought. Unfortunately, most homeowners only go to their attics when there’s a problem, and many times that problem has grown into a serious concern by that point.

So, one of the many problems you can have in your attic is mold. Today, we’ll discuss everything you need to know about mold in attic:

  • Signs of Mold in Attic
  • Causes of Mold in Attic
  • How to Remove Attic Mold
  • How to Prevent Attic Mold from Growing Back
  • Conclusion

So, without any further ado, let’s dive in!

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Signs of Mold in Attic

Most likely, as you may have guessed, these signs will be visible when you look up at your walls and ceilings.

You may see dark patches or stains in the corners of your ceilings. The upper section of your walls may have started to peel off or crack. 

When you step into the rooms below your attic, you may smell that rotten, musty odor and perhaps even start coughing or sneezing. 

This is because mold spores can cause asthma or allergic reactions in those prone to them. So, if you feel like you need to wear a mask when you step into those rooms (or the attic itself), and you see these patches, it’s time to do further inspection (with caution, of course).

Climb up to your attic and look around. If the mold has spread enough to be visible on your ceilings, you should be able to clearly see mold colonies in the attic.

Mold causes the wood to warp and distort. It can also make your insulation less effective if it grows enough.

Okay, good, I’ve spotted it. But what has caused it?

Great question.

Causes of Attic Mold

Mold was likely caused by moisture accumulation of some kind in your attic. The attics have plenty of wood the mold can eat to sustain its growth. All that’s needed is moisture.

For those who don’t know, mold requires organic materials as a food source, and wood contains cellulose and sometimes lignin which are the exact things mold can digest and use as energy.

Cellulose, a primary component of wood and cotton, can be broken down into glucose by mold. That glucose will serve as fuel. Similar goes for lignin.

So, we all know your attics are pretty much all wood. Therefore, if mold growth gets out of hand there, it can become a real problem to repair it all.

But what causes that moisture in the attic? Glad you asked, since there can be a lot of perpetrators:

  1. Inadequate Ventilation:
    • Without proper ventilation, the attic can become stagnant, leading to moisture buildup. Stagnant air prevents the natural drying process.
    • Also, inefficient or improperly designed ventilation systems may fail to adequately expel humid air out of your house. This can then cause problems such as attic mold and bathroom fan leaks.
    • Soffit vents that are blocked by insulation or debris don’t allow the intake of fresh air.
    • Similarly, obstructions near ridge vents can limit the escape of humid air from the attic.
  2. Roofing Leaks:
    • Missing or damaged shingles, cracked flashing, or other compromised roofing parts can allow water to infiltrate the attic during rain.
    • In colder climates, ice dams can form on the roof, preventing melting snow from draining properly. This trapped water can then seep into the attic.
  3. Insufficient Insulation:
    • This can lead to temperature differentials between the attic and the rooms below. This difference can cause condensation as warm air meets cooler surfaces in the attic.
    • Insulation that absorbs and retains moisture also creates problems. Remember, insulation is also made of organic matter like cellulose and wool. This means mold can start eating your insulation too.
  4. Inadequate Vapor Barriers: Lack of proper vapor barriers in rooms below can allow moisture to move up from them and get stuck in the attic.

This is a pretty good list. Make sure to look around. Check your ventilation system and inspect your roof for leaks.

How to Remove Mold from Attic

Attic mold removal is one of the more challenging tasks to carry out. So, we have to say it but you should hire a restoration company for that.

But if you’re still willing to give it a go, here’s how to do it:

  1. Safety First: Wear appropriate safety gear, including a mask (preferably an N95 respirator), gloves, and protective glasses, to prevent inhalation or skin contact with mold spores.
  2. Identify and Fix the Moisture Source: Identify and repair any roof leaks or sources of moisture before removing the mold itself. If you don’t do this, the mold will just keep coming back. Got condensation problems? Fix them. Insulation problems? Fix them. You need to do this so that your hard work in removing mold does not go to waste when you notice mold again after a few months.
  3. Seal Off the Attic: Use plastic sheeting and tape to seal off the affected area from the rest of the home. Then you get to removal work.
  4. Discard Damaged Material: As we’ve mentioned before, mold can penetrate and eat up your insulation and other organic materials. This also likely includes some of your wooden beams. Hopefully, your wood hasn’t suffered much and can be cleaned. Your insulation is likely to deteriorate much more easily but you should be consulting a professional engineer if you see that you can’t save your wooden beams from mold. Also call up a restoration company in that instance.
  5. Use HEPA Vacuum: Vacuum the entire attic space, especially after removing contaminated materials. Use a vacuum with a High-Efficiency Particulate Air (HEPA) filter to capture mold spores and prevent their release back into the air.
  6. Use a Mix of Vinegar and Water: Apply white vinegar to the wood along with warm water. Leave it to sit for some time, and then repeat this process until the mold is killed. Do not use bleach as white vinegar can penetrate through the roof and kill the mold’s roots.
  7. Improve Ventilation: Once you’re done, improve attic ventilation for air to circulate and the now-wet area to dry out more easily. Vinegar should do the deed for most instances.

And there you go. 

How to Prevent Mold from Growing Back to Your Attic

It’s simple. Whatever the moisture source, make sure it doesn’t happen again. 

Repair any roofing leaks and/or improve ventilation. Use insulation baffles to maintain a clear pathway between the insulation and the roof deck.

Make sure condensation doesn’t happen. Opt for thermostat-controlled fans that activate when attic temperatures reach a certain level, resulting in more efficient cooling.


That’s it for today. Hopefully, after this post, you won’t have to deal with attic mold again now that you know how to remove and prevent it for good.

If you need more help with mold removal, check out some of our other posts or connect with a restoration pro near you!

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