Why North-Facing Siding Turns Green in West Knoxville
Walk around almost any house in Bearden or Farragut and you will find one side that looks different. Usually it is the north side, often under a big oak or maple, and the siding has a green or gray-black film on it. That film is mildew and algae, and it is one of the most common reasons people call about pressure washing in Knoxville.
Why it grows there
Algae and mildew need three things: moisture, shade and something to feed on. The north side of a house gets almost no direct sun, so dew and rain sit on it longer. West Knoxville's heavy tree canopy adds more shade and drops pollen and organic debris onto the siding, which gives growth something to hold on to. Add East Tennessee's humid summers and you have close to ideal conditions.
Why painting over it does not work
Paint does not kill mildew. If it goes on over growth, the growth keeps living underneath and works its way back through the new coat, usually within a year or two. It can also stop the paint from bonding, which leads to peeling. That is why every exterior painting job starts with washing.
How it gets cleaned properly
Blasting siding with high pressure knocks the visible growth off but leaves the roots, so it comes back fast. It can also damage vinyl and force water behind it. The better approach is low pressure with a cleaning solution that kills the growth, followed by a thorough rinse. The siding comes out cleaner and stays clean longer.
Keeping it from coming back
- Trim branches back so more light and air reach the siding
- Keep gutters clear so water is not spilling down the wall
- Point sprinklers away from the house
- Wash the house every year or two, more often on heavily shaded sides
If your north side has gone green, or you are planning a repaint, start with a wash. Get a free estimate on house washing in Knoxville.
More from the blog
Pressure Washing vs. Soft Washing: Which Does Your Siding Need?
Concrete can take high pressure. Your siding, painted trim and old mortar cannot. Here is how to tell what each surface needs.
How Often Does a House in East Tennessee Need Repainting?
There is no single number, but there are clear signs. Here is what East Tennessee weather does to paint and when to call.
Patching Sheetrock So the Repair Does Not Show Through the Paint
The raised square, the dull halo, the crack that comes back. Here is why sheetrock patches show and how to make them disappear.
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