If your roof has dark streaks running down it - usually starting on the shaded or north-facing slope - that's not dirt and it's not wear. It's algae, and how you treat it decides whether your roof lasts its full life or gets replaced early.
What the streaks actually are
The organism is an algae that feeds on the limestone filler used in asphalt shingles. It arrives as airborne spores, establishes in shade and moisture, and spreads in streaks down the slope as rain carries it. Left alone it holds moisture against the shingle surface - and a shingle that stays damp ages faster than one that dries out.
Why pressure washing is the wrong answer
Pressure washing a shingle roof strips the protective granules off the surface. Those granules are what block UV; once they're gone the shingle ages rapidly, and the damage is permanent. Some roof warranties are voided by it. If a contractor offers to pressure wash your roof, the correct answer is no.
What soft washing does instead
Soft washing uses low pressure with a treatment that kills the algae at the root rather than blasting the surface. The results keep improving for a few weeks afterward as rain rinses the dead growth away, which is why a freshly treated roof often looks better a month later than the day it was done. Most roofs here want treatment every two to three years.
Metal, tile and other roof types
The method depends on the surface. Metal roofs and tile can take slightly more than asphalt shingles but still don't need high pressure; the goal is always to clean the surface without removing what protects it. We'll tell you which approach your roof needs.
When cleaning isn't the answer
If a roof is already near the end of its life, or has cracked, curled or missing shingles, cleaning won't save it - replacing it will, and we'll say so rather than take the job. Treating algae early is the cheap option; treating a roof that's already failing is money spent on the wrong thing.
Not sure which category yours is in? Send a photo with your quote request and we'll give you a straight answer.
Want it done right the first time? We clean, brighten, dry and seal fences and decks across Central Texas.