One elevation is filthy and the other three look fine. It is not the paint and it is not bad luck. It is four hours of sun a day and a humid climate that never gives the wall a chance to dry.
Stand at the north side of a house in Clayton at eleven in the morning in March. The south wall dried an hour after sunrise. The north wall is still wet, and it will still be damp at two. It never gets a direct hour of sun from October to March, and in summer it gets only the low light at either end of the day.
Algae does not need much: moisture, something to hold on to, and time. It does not need soil and it does not need the wall to be dirty first. Give it a surface that stays wet six hours a day instead of one, and the north elevation becomes the only place on the property where it can establish.
Then the Piedmont piles on. We sit in a humid subtropical climate with long warm shoulder seasons, heavy summer dewfall, and enough pine and hardwood canopy that plenty of houses in Clayton, Garner, and out toward Archers Lodge have a north wall in permanent shade. That is not a maintenance failure. That is the climate doing what it does.
| What you see | What it is | What it means |
|---|---|---|
| Even green film, worse near the ground | Green algae | The most common and the easiest to remove. It is early. Deal with it now and it is a routine wash. |
| Black patches and speckling, often near gutters and under eaves | Mildew and dark mold | Wetter, more established, and it works into porous surfaces and caulk. Still removable, needs proper dwell time. |
| Crusty grey-green circles that feel raised | Lichen | Algae and fungus living together, gripping hard. This is years of growth and it needs chemistry and patience, not force. |
| Green fuzz on the brick and mortar of the foundation | Algae on masonry | Same organism, more porous surface. It goes deeper and wants a longer dwell. |
| Dark vertical streaks from the roofline down | Roof runoff | A different problem. See black streaks on a roof. |
| Tiny raised black dots that will not wipe off | Artillery fungus | Comes from mulch, not from shade. Behaves nothing like algae. |
The cosmetic part is obvious and it is most of why people call. The rest is slower and worth understanding.
If the shaded walkway or patio on that side of the house gets slick after rain, that is the same organism. It is the most common cause of a fall on a residential property and it is entirely preventable.
A pressure washer aimed at a green wall produces an immediate and satisfying result. It also produces a wall that is green again by autumn, because force removes the visible colony and leaves what is rooted in the surface texture. What you have actually done is water it and clear its competition.
A soft wash kills the organism where it sits, then rinses the dead material away. That is why the interval between washes is years rather than months, and it is the only reason the method matters here.
Trim or remove whatever is shading it. Limbing up a tree line so afternoon light reaches the elevation does more than any product will, and it is a one-time job.
Shrubs planted tight against siding trap humidity in the gap and stop air moving. Eighteen inches of clearance changes how fast the wall dries.
A sprinkler head hitting the north wall three mornings a week is the single most avoidable cause of this, and it is extremely common on newer lots.
Overflowing gutters and leaking downspouts keep a strip of wall permanently wet. Clear gutters are part of this problem, not a separate one.
Green algae is a routine wash. Lichen is restoration work. The cheapest time to handle this is always earlier than you think.
Most houses in the Triangle and Johnston County want a wash every one to two years. A house with a heavily shaded north wall, mature tree cover, and a sprinkler that catches the siding can need the shaded elevation more often than the rest of the property, and there is nothing wrong with washing one side on a tighter cycle than the others.
If you are looking at a green wall and wondering whether it is early or late, send a photo. We will tell you which of the three organisms you are looking at and whether it is a wash or a bigger conversation. Call (919) 698-3669.
“They transformed the outside of our house. The siding looks brand new and they were careful around all my flower beds.”
“Came out on a weekend when I needed it and the results were excellent. Real person answered the phone every time.”
“Same-day service and the whole property looks better. Will use them every year.”
Aluminum chalks for a different reason than vinyl does, and the decision at the end is different too. How to test what you have, what a restoration wash actually achieves, and when paint is the honest answer.
Read the guide →HOAWhat a multifamily property actually needs cleaned, how often, and why the surfaces that generate complaints are almost never the ones in the budget.
Read the guide →BookingWhere the truck parks, whose water we use, how long it takes, whether you need to be home, and the short list of things to move, close, or unplug before we get there.
Read the guide →We fly the roofline and show you the footage on the spot. You see your own gutters, joints, and downspouts on the screen instead of taking our word for it. It costs nothing and you are not committing to the cleaning.
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