Those dark streaks making their way across your roof aren't simply weathering or built-up dust, no matter how much they might look that way from the ground. In most cases, it's algae quietly spreading across your tiles or metal roofing, holding moisture against the surface and gradually wearing down the material underneath. What looks like a cosmetic issue is often the early stage of something that shortens your roof's lifespan.

Left alone, that growth rarely stays put. Moss and lichen tend to follow, both of which dig in harder than algae and trap even more moisture against the roof. Professional soft washing clears all of it at the source, rather than just masking the surface, so the results hold up for years instead of fading within a season.