How To Remove Moss, Lichen, and Algae From Roofs Safely

a stone fireplace with moss growing on it

Discover how to remove moss, lichen, and algae from roofs safely using the right cleaning chemistry, gentle agitation, and careful rinsing. These steps protect your roof’s coating, stop leaks, and restore its original colour and finish. By identifying the growth correctly and using a controlled, low-pressure process, you’ll prevent long-term regrowth and maintain roof health for years to come.

Steps On How To Remove Moss, Lichen, and Algae From Roofs Safely

1. Diagnose the Growth Type

Examine the roof closely to identify whether you’re dealing with algae, moss, or lichen. Algae usually appear as dark streaks, moss as thick green clumps, and lichen as flat, crusty discs. Knowing which you have helps you choose the correct dwell time and cleaning strength for safe removal.

2. Apply a Roof-Safe Biocide to Remove Moss, Lichen, and Algae from Roofs Safely

Select a biocide formulated specifically for roof materials and organic growth. Apply it evenly, allowing enough dwell time for full penetration and breakdown of spores. Keep surfaces damp during treatment—never increase pressure to compensate, as this can damage coatings or dislodge tiles.

3. Agitate Only Where Needed

After the dwell period, lightly brush dense moss patches with soft-bristled brushes to lift growth without harming the surface. Avoid metal tools, scrapers, or abrasive pads, especially on coated metal or glazed tiles, to preserve the finish and prevent scratches.

4. Rinse Low and Wide

Rinse with a wide-fan, low-pressure spray directed down-slope to avoid forcing water under laps or flashings. Move methodically from ridge to gutter, ensuring all loosened debris is flushed away. Clean gutters and downpipes thoroughly to prevent blockages and staining.

5. Add Preventative Treatment

Once clean, apply a compatible residual treatment to inhibit regrowth for up to 12–24 months. Improving sunlight exposure by trimming overhanging branches and enhancing airflow will further reduce moisture levels that support moss and algae.

Pro Tip: To remove moss, lichen, and algae from roofs safely, work in two lighter passes a few weeks apart instead of one harsh clean. This gentle approach ensures deep cleansing without stripping coatings or weakening tiles—keeping your roof durable, watertight, and visually appealing.