You may walk down almost any street and notice something odd: one side of the house is dark, while the other is not. It’s weird because both sides of the same house are the same age and have the same paint. The difference is in the way the wall faces.
It’s More Than Dirt
Based on the experience of power washing experts in Stamford, CT, you can’t just wash away the dark spots and vertical streaks on the roof and siding. Many homeowners try to do so but fail. The reason is not just the dirt that seems to cover the walls and roof. These are the living organisms that inhabit the porous building materials.
On roofs, it’s usually a blue-green bacterium called Gloeocapsa magma. It arrives as airborne spores and settles in damp places. In addition, its survival instincts make it create a dark pigmented sheath as protection against UV. On siding, you’re more often looking at mildew and green algae that also “adore” shade and moisture. So, when you rinse your house, you simply water a living colony, not clean it.
Which Side Usually Turns Dark
The most vulnerable part of the house is the one in shadow. These are the walls and roof that face north, as the southern part is in the sun for most of the day. As a result, the morning dew vanishes, leaving the algae little chance to find a suitable environment. The north gets the sunrays only indirectly. So the dew can sit until noon. The situation gets worse after days of heavy rain, when the walls stay wet for a couple of days.
Besides, there are other factors that can create favorable conditions for the unwelcome living population:
- Tall trees that create shadows (even on the other sides of the house);
- Limbs overhanging the roof slope or brushing the siding;
- Gutters clogged with leaves, keeping the lowest courses of shingles soaked;
- A downspout emptying against the foundation instead of away from it;
- Shrubs planted tight to the wall.
So, trim the branches, clear the gutters, redirect the downspout, and cut the shrubs back before you start cleaning the facade.
Why Proper Cleaning Matters
Most homeowners simply rinse their houses to remove the dust. Yet, water cannot solve the problem. In addition, pressure washing can damage the coating of facade materials, leading to their further deterioration.
Professional soft washing involves diluted sodium hypochlorite with a surfactant and low pressure. If the facade is covered with mold and lichen or the material is too delicate, professionals apply other detergents and washing techniques. Physical removal of moss and lichen can do more harm than good, and using sodium hypochlorite on wooden parts can also be unfavorable.
So, you should learn more about the materials your house is built with and the best cleaning technique. Exterior cleaning is not only about the appeal but also about the longevity of the materials. At first, it can be a thin film of dust, but soon, if you neglect cleaning, it will mix with spores of living organisms. Together, they will make the northern part of your facade dark, spread to other parts of the house, and destroy its coating.
