Soft-wash roof cleaning in Little Rock for black algae streaks

The dark stripes running down so many Arkansas roofs come from Gloeocapsa magma, a type of cyanobacteria often just called roof algae. It spreads by airborne spores and feeds on the limestone filler found in many asphalt shingles. As it grows, it builds a dark protective coating that shows up as streaks, usually starting on the north and shaded slopes.

Moss and lichen are different growths that often show up alongside it. Moss holds water like a sponge and can lift shingle edges. Lichen grips the granules tightly and leaves spots behind when it is pulled off the wrong way.

From the street, the streaks are often mistaken for soot, mold or worn shingles. A close look usually settles it, and we confirm what is growing before we price the job.

A pressure washer will take streaks off a roof, but it also blasts away the granules that protect asphalt from the sun. Shingle makers and roofing trade groups advise against it for exactly that reason. A roof that looks clean after a pressure wash can lose years of life in an afternoon.

High-pressure water can also drive under shingle tabs, break the seal strips and push water into the decking. On older roofs, it can tear brittle tabs right off. We skip scrub brushes and stiff brooms on asphalt too, since they grind granules loose in the same way, just more slowly.

Soft washing works the other way. We apply a cleaning solution at garden hose pressure, let it work on the algae, then rinse at low pressure. The chemistry does the work, so the shingles do not take a beating.

If someone pressure washed your roof in the past, we check for bare spots and loose granules and tell you whether any shingles need replacing.

Cleaning solutions strong enough to kill algae need care around landscaping. Before we start, we soak shrubs, flower beds and grass below the drip line with plain water so they absorb less runoff. We cover delicate plants when needed and rinse them again when we finish.

We also check the gutters and downspouts first. Clear drainage carries the runoff away instead of letting it pool near the foundation or splash onto siding.

The solution breaks down fairly quickly after it is rinsed, but common sense still applies: keep pets and kids inside or away from the drip edge until the final rinse is done.

• Pre-wet plants and lawn below every roof edge
• Cover sensitive shrubs, ponds and outdoor furniture
• Apply the solution from the ground or roof at low pressure
• Rinse plants, siding and windows again when we finish

• Black or dark green streaks running down the roof slopes
• Green moss growing along shingle edges or in valleys
• Gray or pale green lichen spots on north-facing slopes
• Streaks are spreading from the shaded side across the whole roof
• You plan to sell and the roof looks older than it is
• The attic feels warmer since the light roof turned dark

Humidity is the main reason. Long, warm, damp summers and mild winters give algae a long growing season, and shade from oaks and pines keeps north slopes wet well into the afternoon. Homes near creeks and lakes, or on wooded lots, tend to streak first.

In most cases, algae is a cosmetic problem rather than a structural one. Heavy growth does hold moisture against the roof, though, and moss in particular can lift shingle edges where wind-driven rain gets underneath. Lighter colored roofs also lose some of their reflectivity once streaks spread, which can mean a warmer attic in July.

Homes with shingles installed before algae-resistant granules were common usually show the heaviest growth. Metal and tile roofs can grow algae and lichen too, and we clean them with the same low-pressure approach, adjusted for the surface.

Cleaning kills the current growth, but spores keep landing. Most roofs in our area start to show faint streaks again within a few years, faster under heavy shade.

Strips of zinc or copper installed near the ridge help slow regrowth. When rain washes over the metal, it carries small amounts of it down the roof, and algae does not tolerate it well. Trimming branches back to let in more sun helps too.

Many homeowners in shaded neighborhoods book a light treatment every two to three years instead of waiting for heavy streaks. Lighter growth takes less solution and less time.

If you are planning a new roof, algae-resistant shingles with copper-containing granules are a good choice for this climate, and we can walk you through the options during a visit.

Sometimes a roof is too far gone to clean. If the shingles are brittle, curling or missing granules across large areas, cleaning will not change what is underneath, and we will tell you that rather than charge you to wash a roof that needs replacing.

We also check for loose flashing, cracked boots and damaged shingles while we are up there. Anything that needs repair gets photographed and priced in writing. Cleaning before you list a home is common too, since streaks make a sound roof look old in listing photos.

Call (501) 387-1152 to set up a roof cleaning, and ask about adding zinc strips on the same visit.

Roof cleaning cost depends mostly on roof size, pitch and how heavy the growth is. These are typical 2026 Little Rock ranges.

Very steep roofs, heavy moss and homes with large landscaped beds below the eaves take more time and cost more. See the full roof pricing guide.