Those black streaks running down your roof aren't dirt, and they aren't a sign the shingles are worn out. They're a living algae called Gloeocapsa magma, and in Statesville's warm, humid climate it spreads from roof to roof fast. Left alone, it darkens the whole roof, holds moisture against the shingles and gives moss and lichen a place to take hold.
The fix is a soft wash roof cleaning. No high pressure, no scrubbing, no walking all over your shingles more than needed.
Why you should never pressure wash a shingle roof
Asphalt shingles are covered with small granules. Those granules protect the shingle from sun and weather. High-pressure water strips them off, and once they're gone, the shingle ages much faster. Pressure washing can also lift shingle edges and drive water under them.
Major shingle manufacturers and roofing industry groups recommend low-pressure cleaning with a bleach-based solution for algae, not pressure washing. That is exactly how soft wash roof cleaning works.
How Statesville soft washing cleans a roof
Prep and protection
Before anything touches the roof, the crew wets down the plants and grass under the drip line. They also take care with gutters and downspouts. Runoff from the roof goes through them, so they keep them flowing and flush them with clean water as they go. If needed, downspouts get redirected away from sensitive plants.
Applying the solution
The technician applies a mild bleach-based roof cleaning solution with a surfactant, at low pressure, from the bottom up. The solution soaks into the algae, moss and lichen and kills them.
Dwell and rinse
On many roofs, the black streaks start fading within minutes. Depending on the roof and the growth, the crew may rinse lightly with low-pressure water, or let rain finish the job over the following weeks, which is common practice for roofs. Plants, siding, walkways and anything below are rinsed thoroughly before the crew leaves.
Moss and lichen
Thin moss usually dies and loosens after treatment. Thick moss mats may need gentle removal by hand. Lichen is stubborn, and it can take several weeks after treatment for it to fully release and wash away with rain. Ask the contractor what to expect for your roof.
Most single-story roofs take a few hours. Steep or two-story roofs take longer and need more setup.
Metal roofs
Metal roofs collect algae, mildew and dirt too, especially on shaded slopes. They're also slippery and the finish can be damaged by harsh scrubbing or high pressure. Metal roofs get soft washed with the same low-pressure approach and rinsed carefully.
Why roof cleaning is worth it
- Looks. Cleaning the roof often makes a bigger visual difference than washing the siding.
- Heat. A darkened roof absorbs more heat in a Statesville summer than a clean one.
- Shingle life. Algae, moss and lichen hold moisture against shingles. Removing them helps the roof last.
- Selling or insuring. A streaked roof can raise questions with buyers and inspectors, even when the roof is sound.
How often to clean your roof
After a soft wash, most roofs in our area stay clean for several years. Roofs under heavy trees or on shady north slopes may start to streak sooner. Keeping gutters clear and trimming back overhanging limbs helps.
Pair it with a house wash or gutter cleaning
Roof cleaning and house washing are a natural pair, since the same algae is usually growing on both. And since the roof drains through the gutters, it's smart to have clean, flowing gutters. Gutter cleaning can be done on the same visit. Many homes with streaked roofs also have mildew on the driveway and walkways.
The price of a roof soft wash depends on the roof's size, how steep it is and how much growth is on it. Our pressure washing cost guide explains what sets the price. Your real price comes from a free on-site or photo quote. Call (980) 223-3324 or request a quote online.
Questions people ask
Will roof cleaning damage my shingles?
Not with a soft wash. A soft wash uses low pressure and a cleaning solution, which is the method shingle manufacturers recommend for removing algae. Damage comes from high pressure, which strips the protective granules. Shingle roofs should never be pressure washed.
How long until the black streaks are gone?
Many streaks fade noticeably the same day. On some roofs, especially with heavy growth or lichen, the remaining stains keep fading over the next few weeks as rain rinses the dead algae away. You'll hear what to expect with the quote.
Is the runoff safe for my plants?
The crew pre-wets plants and grass under the roofline before starting, keeps gutters and downspouts flowing, and rinses everything afterward. The solution is diluted and breaks down quickly. Point out any plants you're especially concerned about.
Do you walk on the roof?
Only as much as needed, and on many roofs the crew can treat most of the surface from ladders or the ground. Steep roofs may require extra safety setup. The contractor will explain the plan for your roof at the quote visit.