Tab shingles are a common type of asphalt roofing material that, like many others, can be prone to algae and moss growth. This happens primarily because these shingles retain moisture, especially in shaded or humid areas, creating a perfect environment for algae and moss to thrive. Algae usually appear as dark streaks or stains, while moss grows as green, fuzzy patches. These growths not only affect the roof's appearance but can also trap moisture against the shingles, which may accelerate wear and lead to shingle damage over time. Simple diagnostics include visually checking shaded or north-facing parts of your roof for discoloration or fuzzy growth. You can also gently run your hand over the surface (from a safe vantage point or ladder) to feel for growth or roughness that should not be there.
For safe DIY checks, use binoculars from the ground or carefully inspect the roof from a ladder, avoiding walking on damaged shingles to prevent voiding your warranty. Light moss can sometimes be removed using a soft brush or spraying a 50/50 mix of water and bleach (followed by a rinse), but be cautious not to damage the shingles or nearby plants. If the algae or moss covers large patches or if you notice damaged shingles, it’s best to call a licensed roofer who can assess the extent and recommend professional cleaning or even shingle replacement if necessary. When speaking with your contractor, consider asking, “What treatment do you recommend to safely remove algae or moss without damaging my warranty?” and “How can I prevent this growth from returning, especially in shaded roof areas?” These questions ensure the approach balances effectiveness with warranty and roof health.