Mildew And Algae Guide For Vinyl Siding

Most homeowners opt for vinyl siding because it looks good and requires very little maintenance. This is why it can be disconcerting if the siding begins to develop black or greenish discoloration. The culprit is usually mildew, algae, or moss. The following guide can help you better understand the problem so you can fix it and prevent it from happening again.

Common causes

Mildew, moss, and algae needs damp and shade to grow. This is why it is often more commonly found on the north side of a home or on a side that is shaded by dense plants or tall trees. This doesn't mean that areas of the home with more sun exposure are immune, simply that they are less likely to experience heavy growth.

Removal method

Fortunately, mildew, moss, and algae stains aren't usually permanent and they aren't likely to damage the vinyl. You can remove the stains and kill the mildew and algae using the following method:

  1. Dilute bleach in water. One part bleach to four parts water should destroy any stains without harming the siding or killing nearby plants.

  2. Put on a pair of rubber gloves to protect your hands.

  3. Scrub the stained area with a soft bristle brush and the bleach solution.

  4. Allow the solution to sit on the siding for 10 minutes or so, and then rinse it off.

  5. Repeat the process if necessary, and then rinse the siding thoroughly.

There are also commercial moss and mildew removers available.

Preventing future growth

The moss, algae, or mildew will return if you don't take steps to prevent it. The following tips can help:

  • Trim back plants that grow near the side of the house so that air can better circulate and keep the area dry.

  • Thin out shade trees to help open up the canopies to allow more light into the home.

  • Periodically rinse off the siding with plain water so that dust and mildew spores don't buildup.

  • Install gutters so rainwater doesn't keep the side of the house wet.

  • Position sprinklers so they do not spray onto the siding and increase the moisture on the home.

  • Avoid fertilizer splash on siding because the phosphates in the fertilizer can lead to increased mildew and algae bloom.

You may never be able to stop the growth entirely on a damp, shaded vinyl clad wall, but you can minimize it so that cleanup is relatively easy. Contact a siding contractor for more help.


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