Mold & Mildew on Exterior Walls in Hawaiʻi: What to Do

Hawaii's Mold Problem

If you've noticed dark streaks, green patches, or fuzzy growth on your home's exterior walls, you're not alone. Hawaii's warm, humid climate creates ideal conditions for mold and mildew growth.

Understanding the Difference

Mildew

• Typically gray or white
• Grows on the surface
• Flat, powdery appearance
• Easier to remove

Mold

• Usually black, green, or dark colored
• Can penetrate surfaces
• Fuzzy or slimy texture
• More stubborn to remove

Why It Happens in Hawaii

Humidity

Our year-round humidity (often 70-80%) provides constant moisture for growth.

Shade

Areas that don't get direct sunlight stay damp longer.

Rain Exposure

Frequent rain, especially on windward sides, keeps surfaces wet.

Poor Airflow

Tight spaces between buildings or landscaping too close to walls.

Where It Commonly Appears

• North-facing walls
• Areas shaded by trees or structures
• Under eaves and overhangs
• Near sprinkler systems
• Lower portions of walls near ground
• Stucco and textured surfaces

Health and Home Concerns

Health Issues

Mold can trigger:

• Allergies and respiratory problems
• Asthma symptoms
• Skin irritation

Home Damage

Untreated mold can:

• Stain surfaces permanently
• Degrade paint and coatings
• Damage siding materials
• Spread to interior walls

Removal Methods

DIY for Small Areas

For minor mildew spots:

1. Mix 1 cup bleach with 1 gallon water
2. Apply to affected area
3. Let sit 15-20 minutes
4. Scrub gently with soft brush
5. Rinse thoroughly

Caution: Bleach can harm plants and discolor certain materials. Always test in an inconspicuous area first.

Professional Soft Washing

For larger areas or persistent problems, professional soft washing is recommended:

• Uses specialized, biodegradable solutions
• Kills mold and mildew at the root
• Won't damage siding or paint
• Results last longer than DIY methods
• Treats entire surfaces evenly

Why Not Pressure Wash?

High-pressure washing can:

• Drive water and mold spores into walls
• Damage paint and siding
• Create conditions for faster regrowth

Soft washing with proper solutions is far more effective.

Prevention Strategies

Improve Airflow

• Trim bushes and plants away from walls
• Remove debris that traps moisture
• Ensure proper gutter drainage away from walls

Reduce Moisture

• Fix sprinklers spraying on walls
• Repair any leaks promptly
• Ensure proper roof drainage

Increase Sunlight

• Trim overhanging branches
• Consider removing or relocating shade-creating plants

Regular Cleaning

• Address growth early before it spreads
• Schedule routine exterior cleaning
• Rinse walls occasionally with fresh water

Protective Treatments

Some professional cleaners offer mold-resistant treatments that can slow regrowth.

When to Call a Professional

• Growth covers large areas
• It keeps returning after DIY attempts
• You see mold inside your home too
• The surface is delicate (stucco, painted wood)
• You're not comfortable working with cleaning chemicals

What to Expect from Professional Cleaning

1. Assessment of affected areas
2. Protection of plants and surrounding surfaces
3. Application of cleaning solution
4. Dwell time for solution to work
5. Soft-wash rinse
6. Optional protective treatment

Maintenance Schedule

For Hawaii homes, exterior cleaning every 6-12 months helps prevent mold from becoming established. Homes in particularly humid or shaded areas may need more frequent attention.

Bottom Line

Mold and mildew are common in Hawaii but don't have to take over your home. Regular maintenance and prompt treatment keep your home looking good and protect your family's health.

Contact Mālama Home Solutions for professional soft washing and mold prevention services.