Mold isn’t just a cosmetic problem—it’s a sign that moisture is creeping in where it doesn’t belong. Left untreated, it can damage drywall, weaken wood, and create serious health issues. If you’re asking, what does mold look like on walls, you’re already taking the right first step.
And when it comes to exterior walls, the risks multiply. Mold on stucco, siding, or painted concrete often points to clogged gutters, poor drainage, or cracks letting moisture in.
So, what does mold look like on walls, exactly? It varies depending on the type and the surface, but here are the most common visual signs:
Still not sure? Take a photo and compare it to known mold types—or call a professional to assess it.
This is one of the most common questions we get. You’re staring at your siding or basement wall wondering, what does mold look like on walls—and is that even mold?
Here’s a quick test: try wiping it with a damp cloth.
Exterior mold tends to cling to porous surfaces like brick, stucco, and wood, so even if it wipes off, the roots may remain.
Knowing what does mold look like on walls is just half the battle—you also need to know where to look. On the exterior of a home or commercial building, mold tends to form:
If you see discoloration in these areas, mold might be brewing beneath the surface.
You may think: it’s outside, how bad can it be?
The truth is, exterior mold spores travel—and they’ll find a way inside if given the chance.
Ignoring mold can lead to:
So if you’ve Googled “what does mold look like on walls” and realized your siding matches the description… it’s time to act.
Here’s what to do if you’ve spotted mold:
Take note of color, size, and texture. Check nearby areas for water sources or damage.
Wear gloves, goggles, and a mask—even outside. Mold spores spread easily.
Try a mix of white vinegar and water (1:1), or a commercial cleaner with sodium hypochlorite.
Use a stiff-bristled brush. Don’t pressure wash unless you know the surface can handle it.
Use a hose to rinse, then let the wall dry completely to prevent regrowth.
It’s easy to confuse mold and algae, especially when they’re both green. But they’re not the same.
If you’re unsure whether it’s mold or algae, look for the odor (mold smells musty), and whether it spreads quickly in moist, shady areas. Either way, Insight can treat both safely and effectively.
It might—if the root cause isn’t fixed. Mold thrives in moist environments, and unless you address the underlying moisture, it will reappear.
That’s why our team doesn’t just wash your walls—we check for clogged gutters, poor drainage, and cracks in your exterior that allow water in. Preventing mold is as important as removing it.
DIY works for small patches. But if:
… it’s time to call in a pro.
At Insight, we don’t just remove mold—we prevent it from coming back. Our team is trained to identify the root causes and safely eliminate buildup from even the toughest surfaces.
How can I tell if it’s mold or mildew on my wall?
Mildew is usually lighter in color and stays on the surface. Mold is darker, fuzzier, and penetrates deeper.
Can mold grow on painted walls outside?
Yes. Paint can temporarily hide moisture, but mold can still grow beneath or push through.
Is mold on walls dangerous?
Yes—especially black mold. Even outdoor mold can trigger allergies or spread inside.
How do professionals remove mold from walls?
We use eco-safe solutions, soft-washing or pressure washing (depending on the material), and sealants to prevent future growth.
You don’t have to live with mold or guess how to fix it. Whether you’re dealing with stucco, siding, or concrete walls, Insight Service Solutions is here to help.
View our full Pressure Washing services
Request a quote and get started today
Built on Clean. Trusted Across Winnipeg.
From rust stains to mold patches, we’ve seen—and solved—it all. Call Insight Service Solutions for honest advice, spotless results, and curb appeal that lasts.