Black Roof Streaks (Gloeocapsa magma) — Myrtle Beach Homes
Black Roof Streaks (Gloeocapsa magma) — Myrtle Beach Homes — what this page covers
Roof streaking in humid beach climates is Gloeocapsa magma. A soft-wash treatment kills the bacteria at low pressure; pressure washing the roof blasts the stain off but also erodes the granules that protect the shingles — and most shingle warranties are voided by high-pressure cleaning. Problems with roof cleaning rarely start with the surface itself — prep and materials are usually behind them, and the fixes below are the ones that hold.
Signs you have this problem
Black vertical streaks running down asphalt shingle slopes
Most visible on the north and west roof faces
Not moss and not soot — living cyanobacteria feeding on shingle limestone filler
Spreading colonies shorten roof life by holding moisture against shingles