Black streaks on San Diego roofs are unsightly — and many homeowners assume the solution is pressure washing. It's not. It's soft-wash with cleaning solution. Here's why.
What black roof streaks actually are
Gloeocapsa magma. It's an algae that grows on roof surfaces in coastal climates. Once established, it spreads quickly along shingle valleys and northern roof faces (less sun exposure).
What pressure washing does
Strips the protective ceramic granules off shingle surfaces. Damages tile glazing. Can dislodge ridge tiles. Forces water under shingles. Voids most manufacturer warranties.
Visual: looks clean for 2-3 weeks. Algae returns. Now your roof is damaged AND streaky.
What soft-wash does
150-300 PSI water + sodium hypochlorite-based cleaning solution. Kills algae at the cellular level. Rinses clean. No damage to shingle granules, tile glazing, or any structural component.
Visual: clean for 12-18 months. Slow re-growth that we can prevent with copper strips at the ridge.
Cost comparison
Roof pressure wash: $250-450 typical job.
Roof soft-wash: $385-685 typical job.
Cost difference: $150-200.
Damage prevented: shingle replacement $8,000-15,000. Hidden water damage from pressure forcing water under shingles: $3,000-12,000.
The math
$150 more for soft-wash = save $8,000+ in shingle damage. Easiest decision in roof maintenance.
If a pressure washing company quotes you a roof pressure wash, that's a red flag — not a value.
Free roof assessment. We tell you straight whether soft-wash is right + quote in writing.
Need roof soft-wash in San Diego?
We're Bayside Pressure Wash — family-owned, fully licensed, and answering the phone live. Most San Diego jobs booked same-day.