Quick Answer
Okay so here's the quick version. That green or black gunk on your vinyl siding is algae and mildew, and it loves shade and moisture. For light stuff, a bucket of water and vinegar works. For the heavy-duty nastiness, you'll need a real siding cleaner. The rust streaks? That's from metal dripping on it. You can do this yourself for maybe $30-100 in supplies, but don't just grab a pressure washer and go nuts. You can do some real damage. A pro will charge you anywhere from $200-600, but they'll do it right.
Common Symptoms
Possible Causes
Step-by-Step Diagnosis
Step 1
Perform a full walk-around inspection of the house to identify all affected areas and look for environmental factors like shade or overgrown plants.
Step 2
Identify the type of stain by its color and location. Green is typically algae, black is mildew, and orange/red streaks are rust.
Step 3
Look directly above any rust stains to locate the source, such as a rusty nail, screw, or piece of metal flashing.
Step 4
Gently press on the siding to check its condition. If it's old, brittle, or makes a crackling sound, you'll need to use a much gentler cleaning method to avoid damage.
DIY vs Professional Costs
| Repair Type | DIY Cost | Professional Cost | Time Required |
|---|---|---|---|
General Siding Cleaning | $10-50 | $150-400 | 2-4 hours |
Heavy Mold/Algae Removal | $30-100 | $300-700 | 3-6 hours |
Rust Stain Removal | $15-40 | $250-500 (often add-on) | 1-3 hours |
When to Call a Professional Siding
- If your house is two or more stories tall, due to the safety risks of working on high ladders.
- If the siding is old, faded, or brittle, as a professional will know how to use low-pressure 'soft washing' techniques to avoid causing damage.
- When the staining is severe and covers a large portion of the house, making a DIY job impractical and time-consuming.
- If you've cleaned the siding yourself but the mold or algae returns quickly, indicating a persistent moisture problem that may need an expert opinion.
Prevention Tips
- Trim trees and shrubs at least one to two feet away from the house to allow for better airflow and sunlight.
- Clean your gutters at least twice a year to prevent clogs and water overflow from running down the siding.
- Adjust lawn sprinklers to ensure they are watering the lawn and not constantly spraying the side of the house.
- Perform a light annual rinse with a garden hose to wash away surface dirt and pollen that can feed mold and algae.
Frequently Asked Questions
Related Guides
Choosing a Qualified Siding Repair Contractor: A Guide for Homeowners Troubleshooting & Fixes (2024 Guide)
A veteran technician's guide to choosing a siding repair contractor. Learn how to spot scams, verify credentials, and get a fair price for quality work.
Annual Siding Inspection for Damage and Maintenance Needs Troubleshooting & Fixes (2024 Guide)
A veteran tech's guide to your annual siding inspection. Learn to spot damage, what causes it, and when you can DIY a fix versus when you need to call a pro.
Siding Leaks: Identifying and repairing water intrusion through exterior siding materials. Troubleshooting & Fixes (2024 Guide)
A veteran technician's guide to finding and fixing siding leaks. Learn the symptoms, causes, and when it's a DIY job versus when to call a pro.
Common Siding Problems & Solutions: A Homeowner's Troubleshooting Guide covering various types of siding damage, their causes, and repair options. Troubleshooting & Fixes (2024 Guide)
A veteran technician explains common siding problems like cracks, warping, and rot. Get real-world troubleshooting tips and repair costs for your home's siding.
Siding damage due to external impacts like trees or accidents, leading to visible defects and potential structural or moisture issues. Troubleshooting & Fixes
Siding Took a Beating from a Storm? Troubleshooting & Fixes from a Guy Who's Seen It All
Storms beat up your siding? Here's a veteran tech's guide on what to look for, how to fix vinyl and fiber cement, and when to call for backup.
Need Professional Help?
Find top-rated siding experts in your area