Shade, humidity, and a long damp season are exactly the conditions mold and lichen want, and a cabin under tree cover gives them all three. The green film on the north wall and the black spotting on the walkway are living growth, which is why they come back so fast when someone just blasts them off with water.
Mold, mildew, algae, moss, and lichen stains can be removed from outdoor surfaces safely with Citra-Shield Cleaning Systems ®, a no rinse cleaner and stain remover. It goes on, it works, and it does not need to be scrubbed off or rinsed down.
That last part matters more than it sounds. A rinse means runoff, and runoff on a mountain lot goes downhill into whatever is below it: plantings, a septic field, a creek, or the neighbor. Not having to rinse takes that whole problem off the table.
Stone is where this shows up worst and cleans up best. The foundation above sits on the shaded side of the cabin, a few feet from ground that is still carrying moss, which is exactly the spot algae and lichen keep coming back to.
People use the two words for the same thing, and they are not. Pressure washing removes what is sitting on the surface. Treatment kills the organism that is growing into it. On a wall with real lichen or moss, washing alone takes the top off and leaves the root structure in the grain, which is why it is back within the season.
Most jobs use both. We treat the growth, then wash where a rinse is appropriate, and the difference is that the wall stays clean into next year instead of next spring.
Lichen is the stubborn one. It bonds to stone and shingle and it does not lift in one pass, so heavy growth sometimes needs a second application. We will tell you when we are looking at that rather than promising one visit and coming back for a second.
Moss on a roof or a north-facing wall is a signal worth reading, because it means that surface is staying wet. Sometimes the real fix is trimming back what is shading it.
The log siding, stone foundation, and porch ceilings on our Blue Ridge exterior cabin cleaning job show what this looks like finished. More of it is in the project gallery.
We cover the North Georgia mountains, plus the nearby corners of western North Carolina and southeast Tennessee. The shaded areas on the map are the ZIP codes we serve. Tap or hover on any area to see the town.
Send photos of the growth through the estimate form, close enough that we can see whether it is algae film or lichen. Those need different approaches and the photo usually tells us which one you have.