How To Clean Algae And Mold From Vinyl Siding

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Protect Your Siding by Removing and Preventing Algae and Mildew

Vinyl siding is an excellent choice for keeping your home exterior in great shape for years to come, without a lot of maintenance. But don't forget, any type of siding is just like any other part of your home — it needs proper care to ensure it lasts as long as possible, as attractively as possible. And that means keeping an eye out for something you might not have realized could affect your home siding — algae and mildew.

Fortunately, vinyl siding's low maintenance nature means it's not that complicated to address the growth of algae and mildew. Here's what you need to know.

What are algae and mildew?

Algae is a photosynthetic organism that grows in moisture. You may recognize it as the green growth atop a still pond, for example. Some forms of algae are harmless, but other forms generate unhealthy toxins.

Mildew is a fungus that commonly grows on plants and other damp organic materials, such as paper and leather. It can grow even on the tiniest bits of organic matter.

What causes algae and mildew to grow on siding?

To put it simply, algae and mildew both grow in areas that are damp and organic. So, wood siding — because it's organic — will be especially susceptible to this issue. But other forms of siding are not necessarily immune.

While vinyl and fiber cement are not organic substances, they can both accumulate dust, dirt, and other small specks of natural materials. Those sticky drops that you find on your car at certain times of the year? They consist of tree sugars and sap. They can land on your vinyl and fiber cement siding. And algae and mildew can form on those small specks of tree sap and sugar.

Why does it matter if my home siding has algae or mildew on it? Won't my siding resist it?

Unfortunately, no. These growths can occur in many places you wouldn't expect them to be, even on vinyl siding. And they can cause homeowners a number of headaches:

It's unsightly. Homeowners naturally want a beautiful home that looks great from the curb. Algae and mildew create stains that look unattractive.
It's unhealthy. Algae can produce toxins, which is why an algae-covered lake may be closed to the public. And mildew can cause allergic reactions and skin irritations.
It's a warning sign. While the growth of algae and mildew doesn't automatically mean there's a problem, it can mean that your home is trapping moisture underneath the siding. This is an issue with homes that don't have a proper weather barrier installed underneath the siding — which is common in older homes as well as homes where the siding was not properly installed.

How do I know if my siding has algae and mildew on it?

Look for stains. Stains are the most common sign that you have algae or mildew. The stains can be different colors, which can often tell you what is causing the growth.

Brown stains on wood siding can signal that moisture is forming underneath the wood.
Black stains are usually a sign of mildew, algae, mold or fungus.
Green stains are almost always the result of algae or moss. You're most likely to see green stains on siding that is inadequately ventilated.
Yellow stains mean you probably have damaged insulation or deteriorating sheathing behind the siding.
Stains the same color as your siding are typically caused by water streaming down siding due to damaged or misaligned gutters. These leaks can get behind your siding and eventually cause mildew or mold.
Rust-colored stains are usually a sign that nails in the siding are rusting. This may or may not mean you have excess moisture leading to mildew.

How do I remove algae and mildew safely from my siding?

Avoid the temptation to use a power washer, which can further damage vinyl siding and fiber cement siding. Instead, give your siding a gentle scrub and rinse with a hose.

Choose a cleaning solution that is appropriate for the type of growth you have on your siding:
Water stains — Remove with a mild detergent and water.
Stains on wood — Cleanse with mild detergent mixed with water.
Mildew and algae on vinyl and wood— Use a solution made of oxygen bleach (not chlorine bleach) mixed with water.

What can I do to prevent the growth of algae and mildew on my home's exterior?

Keep in mind, cleaning your siding isn't enough. The long-term solution to algae and mildew growth on your vinyl siding includes identifying and repairing the root cause.

Prune tree limbs and bushes so that they don't press up against your home.
Wash your home at least once a year with a liquid soap and garden hose to remove tree sap and other contaminants.
Inspect your vinyl siding and ventilation ducts for evidence of damage, looseness, or other issues that could contribute to trapped moisture.
Maintain gutters by removing trapped leaves, repairing broken drainpipes, and ensuring the gutters direct water away from your home's exterior.
Adjust sprinklers to be sure they are not striking your siding.
Consult with a home siding contractor that is skilled in installing and repairing siding issues and knows how to find and fix problems with your siding that are caused by excess moisture.

The expert team of siding installers at JD Hostetter are always at the ready to answer your questions, inspect your vinyl siding, and help you figure out what your home needs to keep it gorgeous and long-lasting. To see if JD Hostetter is the right siding contractor for your Indianapolis home exterior needs, contact us anytime at 317-517-7847 to schedule a free consultation, including a detailed estimate and timeline.