Duncan Roof Algae & Black Streak Treatment

Black or dark grey streaks on roof shingles are caused by Gloeocapsa magma — a photosynthetic cyanobacterium that feeds on the limestone filler in asphalt shingles. It's wind-spread and extremely common on Vancouver Island due to the marine-humid climate.

Gloeocapsa magma itself causes gradual degradation of asphalt granules over years. While early-stage streaking is cosmetic, established algae colonies consume shingle material and significantly reduce roof life. Treatment is recommended as soon as streaks are visible.

Laundry detergent can lighten algae streaks temporarily but doesn't eliminate the organism at the cellular level — streaks return within one wet season. Professional biocide formulations used by Roof Labs Canada achieve permanent elimination with 2-year residual protection.

Application takes 2–4 hours for a standard residential roof. Visible results appear over 60–90 days as the treated organisms die and shed. In heavy rain periods (common on Vancouver Island), results are visible faster.

Our professional treatment deposits a residual barrier that prevents re-establishment for 2+ years. All Roof Labs Canada algae treatments include a 2-year written guarantee — if algae returns within 24 months, we re-treat at no charge.