Those black streaks running down so many North Texas roofs are not dirt, and they are not a sign that your roof is failing. In most cases they are algae. The question homeowners ask us next is simple: how do I get rid of it without hurting my roof? The answer depends on one thing, how much water pressure touches your shingles.
What causes the black streaks?
The streaks are usually a type of algae that spreads through the air and settles where moisture lingers. That is why it shows up first on north facing slopes, shaded areas, and spots under trees. Rain carries it down the slope, so the streaks get longer and darker each season. Moss and lichen can follow, and moss in particular can lift the edges of shingles over time.
Why pressure washing a roof is a mistake
Asphalt shingles are covered in mineral granules. Those granules are what protect the asphalt underneath from the sun. A pressure washer is strong enough to blast them loose. Once they are gone, they do not grow back, and the shingle ages faster.
The Asphalt Roofing Manufacturers Association (ARMA) says high pressure washing systems are likely to damage asphalt roofing and should not be used to clean shingles. Pressure washing can also drive water up under the shingle tabs, and it often removes the visible stain while leaving the growth itself behind.
How soft washing works
Soft washing uses about the same pressure as a garden hose. Instead of force, it relies on a cleaning solution that treats the algae, moss, and lichen directly. This is the approach the roofing industry points homeowners toward. Algae streaks typically clear quickly. Moss and lichen release over the following weeks as they die off and wash away with the rain.
- Pressure washing: blasts granules off the shingles, can force water under the tabs, and removes the stain more than the growth.
- Soft washing: low pressure, gentle on shingles, treats the growth itself, and protects your landscaping before work begins.
Why it matters who cleans your roof
Most roof cleaning is done by exterior cleaning companies. That is fine for driveways and siding, but your roof is a system, and what is happening under the stains matters. When a roofing company cleans your roof, trained eyes are looking at more than algae. Lifted shingles, cracked pipe boots, worn flashing, and hail damage are easy to spot when you know what you are looking at.
At Branded E®, we are a GAF Master Elite® contractor, a CertainTeed ShingleMaster Pro, and a FORTIFIED Roofer, which places us among the top 1% of roofing contractors in the United States. If we see something that needs attention while we are up there, we will show you a photo and tell you straight. If your roof only needs a cleaning, that is all we will recommend.
When soft washing is the right call
- Your roof is in good shape but the streaks make the house look older than it is
- You are getting ready to sell and want better listing photos
- You received an HOA notice about roof stains
- Your roof is fairly new and you want to keep it looking that way
If your roof has hail damage, heavy granule loss, or curled shingles, cleaning will not fix that. In those cases we recommend an inspection first so you know exactly what you are dealing with.
Get a soft wash quote
Learn more about our roof soft washing service, or request a quote. Selling a home? Real estate agents can see our soft washing for listings.