If you’ve noticed green streaks, patches, or discoloration appearing on your home’s siding, you’re not alone.
One of the most common questions homeowners throughout Waukesha, Brookfield, Pewaukee, Delafield, Oconomowoc, and surrounding Southeastern Wisconsin communities ask is:
“Why is my house turning green?”
The good news is that your home likely isn’t damaged. In most cases, the green color is caused by algae growth that can be safely removed with professional house washing.
What Causes Green Algae on House Siding?
The green discoloration you see is typically a type of airborne algae that thrives in damp, shaded environments.
Over time, algae spores land on your home’s exterior and begin growing when conditions are right. This is especially common on:
- North-facing walls
- Areas shaded by trees
- Sections of siding that stay damp after rain
- Homes near lakes, ponds, or wooded areas
- Vinyl, aluminum, fiber cement, and composite siding
Wisconsin’s humid summers, rainfall, and changing seasons create the perfect environment for algae growth.
Why Does It Usually Start on One Side of the House?
Many homeowners notice the green staining first appears on the north side of their home.
That’s because the north-facing side typically receives less direct sunlight, allowing moisture to remain on the surface longer. Algae thrives in these damp conditions and can spread gradually across larger areas of siding.
You may also notice increased growth behind landscaping, near downspouts, or under roof overhangs where moisture tends to linger.
Is Green Algae Harmful?
While algae itself is usually not immediately damaging, allowing it to remain on your siding for years can create several problems:
Reduced Curb Appeal
Green staining can make an otherwise beautiful home appear neglected and older than it actually is.
Surface Deterioration
Organic growth can trap moisture against exterior surfaces, which may contribute to premature aging of paint, siding, and trim materials.
Increased Cleaning Difficulty
The longer algae remains on a surface, the more difficult it becomes to remove completely.
Potential Mold and Mildew Growth
Algae often appears alongside mold, mildew, and other organic contaminants that can continue spreading if left untreated.
Can I Pressure Wash It Off?
Many homeowners assume pressure washing is the solution. However, high-pressure washing can potentially damage siding, force water behind exterior materials, and void certain manufacturer warranties. Professional exterior cleaning companies typically use a process called soft washing instead.
What Is Soft Washing?
Soft washing uses specialized cleaning solutions and low-pressure application methods to eliminate algae at its source.
Unlike traditional pressure washing, soft washing:
- Kills algae rather than just blasting the surface
- Cleans deeper into porous surfaces
- Uses significantly less pressure
- Is safe for most siding materials
- Produces longer-lasting results
The cleaning solution breaks down organic growth and allows it to be safely rinsed away without risking damage to your home’s exterior.
How Often Should a House Be Washed?
Most Southeastern Wisconsin homes benefit from professional house washing every 1 to 3 years.
Factors that may require more frequent cleaning include:
- Heavy tree coverage
- High humidity areas
- Homes near water
- Significant shade exposure
- Previous algae issues
Regular house washing helps maintain curb appeal, protects exterior surfaces, and keeps your home looking its best year-round.
How Can I Prevent My House From Turning Green Again?
While no home is completely immune to algae growth, you can help reduce future buildup by:
- Trimming trees and shrubs away from siding
- Keeping gutters functioning properly
- Improving drainage around the home
- Reducing areas where moisture remains trapped
- Scheduling routine exterior cleanings
Preventative maintenance is often far less expensive than allowing years of buildup to accumulate.
Professional House Washing in Southeastern Wisconsin
At DeMark’s Window & Pressure Cleaning, we have helped homeowners throughout Waukesha County and Southeastern Wisconsin safely remove algae, mold, mildew, and exterior staining since 2007.
Our professional soft washing process is designed to restore your home’s appearance while protecting the surfaces underneath.
If your house is starting to turn green, now is the perfect time to address the problem before the staining becomes more noticeable.
Request Your Free House Washing Quote
Whether your home is in Waukesha, Brookfield, Pewaukee, Delafield, Hartland, Oconomowoc, New Berlin, Muskego, Menomonee Falls, or the surrounding Lake Country area, our team can help restore your home’s curb appeal.
Get your free quote today and see why homeowners throughout Southeastern Wisconsin trust DeMark’s Window & Pressure Cleaning for safe, professional house washing services.
