How to Get Mildew Off Vinyl Siding Safely

If the north side of your house has gone green or developed black streaks, you're looking at mildew and algae, and you're not alone. Mississippi's humidity, shade trees, and long warm seasons make it almost unavoidable. The good news is that it comes off. The bad news is that the most popular method, blasting it with a pressure washer, is also the one most likely to damage your siding.

Here's how to get mildew off vinyl siding safely, what to avoid, and when it makes sense to hand the job to a pro.

What you're actually cleaning

The green film is usually algae, and the black spots and streaks are usually mildew. Both are living growths that feed on the dust and pollen stuck to your siding. That matters because just knocking off the visible layer leaves the roots behind, and the growth comes back in weeks.

Whatever method you use, the goal is to kill the growth, not just move it around.

Why high pressure is the wrong tool

Vinyl siding is made of overlapping panels. Hit it with high pressure from below or at an angle and you force water up behind the panels, where it soaks the wall sheathing and can grow mold where you'll never see it. High pressure can also crack older, brittle vinyl, strip caulk around windows, and leave visible stripes where the wand passed.

A pressure washer is a great tool for concrete. Siding is a different job. We break down the full difference in soft washing vs pressure washing.

The safe DIY method for small areas

For a small patch you can reach from the ground, you can get good results with a siding cleaner from the hardware store and a soft brush.

• Wet down any plants near the work area first
• Apply the cleaner with a garden sprayer, working from the bottom up to avoid streaks
• Let it sit for the time on the label so it can kill the growth
• Scrub gently with a soft brush
• Rinse from the top down with a garden hose

Skip the ladder. A spray bottle on a ladder is how weekends end in the emergency room, and ground-level work covers more than you'd think with a sprayer's reach.

What to avoid

• High pressure tips on siding, especially aimed upward
• Undiluted bleach, which can streak siding and kill your landscaping
• Abrasive pads or stiff brushes that scratch the vinyl's surface
• Cleaning in direct hot sun, which dries the cleaner before it can work

How pros do it: soft washing

Professional house washing uses a method called soft washing. A cleaning solution is applied at low pressure, about what comes out of a garden hose, and given time to kill the mildew and algae at the root. Then everything is rinsed gently. No water forced behind panels, no cracked siding, and because the growth is dead instead of just displaced, the clean lasts one to two years in our climate instead of a few weeks.

A careful crew also wets your plants before and after, matches the solution strength to each surface, and rinses everything thoroughly.

Keeping mildew from coming back fast

• Trim shrubs and branches so air and sunlight reach the walls
• Keep gutters clean so they don't overflow onto the siding
• Aim sprinklers away from the house
• Wash every one to two years before the growth gets thick

If green keeps showing up right under your roofline, your gutters are overflowing onto the siding. Our post on why siding turns green in Mississippi explains the connection.

When to call a pro

If the mildew covers a whole wall, reaches the second story, or keeps coming back, a professional soft wash is faster, safer, and longer lasting than DIY. Our house washing service soft washes vinyl, brick, and painted siding across DeSoto County, and a quote by text is free. We're in Southaven, Olive Branch, and Hernando every week. Text us a photo of your house and we'll send a free quote, usually the same day.