4 Reasons Why Mold Grows On Your Vinyl Siding

By Patrick Juma, Dec 12, 2018

QMy house was built 23 years ago. In the last couple of years, I have noticed that, some kind of black/brown spots, mold or mildew has formed on the vinyl siding, especially on the north side of the house. What is the cause and how can I clean them off? If it involves chemicals or is physically challenging , can I hire someone to remove them?
Edmonton ,AB

Before / After Photo of Siding

A: Plastic or vinyl siding is a popular building material because it is affordable and durable. Though it is sold as a maintenance free building material, it too is susceptible to the vagaries of its surroundings. The green /black /brown spots are mildew/mold and they grow on the vinyl due to the following reasons;


The mold and algae are attracted to the sidings because of the dirt ,dust and sugars that are attached to the vinyl. Most people may be unaware that trees and other vegetations release into the air ultrafine particles of sugars at different times of years. Some of these sugars settle on the vinyl . If your house is near trees, some sugary sap from those trees could end up on the siding, these are delicious food for the mold and algae! It is thus important to regularly clean your sidings, preferably once a year.


Mold and mildew thrive in areas with less sunlight.

It is generally a greater problem on the north side of a house than on the south side. This is because, the sun's rays strike the earth's surface nearly perpendicular close to the equator. As you move away from the tropics, the sun’s rays intersect the earth at an angle.

Here in Edmonton, AB or Northern hemisphere the sun is not directly overhead, but to the south, so the south side of any object will get more sunlight than the north. This is why mold likes the north side of the house.

If you have some trees ,a shed or porch roof that keeps one side of the house from receiving sunlight, then you will have a fungus problem. The trees and shrubs can also transfer water to the exterior walls and encourage mold growth.


Another reason that may be causing the mold to grow on your vinyl siding is that there is moisture around the surface. Check to confirm that your gutters are not overflowing or constantly dripping water on the siding. Check for a broken water pipe that could be keeping the siding wet . There is possibility , that rainwater or water from incorrect pressure washing got trapped behind the siding or even within the material. This could create an ideal condition for mold or mildew to grow.


Mildew or mold on vinyl siding is also a sign that a lot of dirt has accumulated on the surface. Mildew or mold often feeds on dirt and dust.


Periodic washing of vinyl sidings with a solution of liquid dish soap and water will prevent mildew and algae build up.

To remove the mold, Vinyl Siding Institute, recommends that, a simple vinegar and water solution is effective in cleaning mold from vinyl siding.

Repair any broken pipes and drain near the vinyl surface .Adjust lawn sprinklers as necessary to keep them directed away from your home.

Ensure that your gutters are clean and in good working order. Clogged or leaking gutters can cause rainwater to run down your exterior walls and can increase moisture levels on and under your siding

Regularly trim your trees and shrubs to minimize shaded areas that can encourage mold growth.

For serious mold problems on your vinyl siding, don’t hesitate to call in the professionals at All Clean Property Services. You can also check out the All Clean Property Services blog for additional Siding Cleaning and mold control tips, including the How Often Should I Pressure Wash or Clean My Vinyl Siding?, Can Pressure Washing Damage Vinyl Sidings and Windows? and How Much Does Window Cleaning Cost In Edmonton?

We have the experience necessary to ensure that the job is done right and that you are satisfied with your new appearance.

About the author
Patrick Juma

Patrick Juma, The founder & CEO of ALL CLEAN Property Services. You can find him on Linkedin.

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