After a wet, cool spring and early summer across Missouri and the Four-States area, many homeowners are noticing something new: green patches creeping across their shingles, or dark streaks running down the slope of their roof. It's easy to dismiss as cosmetic. It's not.
Roof moss and algae are two different problems, but they share the same result — shortened roof lifespan, accelerated shingle damage, and repair bills that grow the longer they're ignored.
Moss vs. Algae: What's the Difference?
Algae (most commonly Gloeocapsa magma): appears as black or dark gray streaks running down the face of your shingles. It feeds on the limestone filler in asphalt shingles and spreads through airborne spores — which is why it often starts in one spot and gradually works across the entire roof.
Moss looks like what it is: a thick, fuzzy green growth that takes hold in shaded or north-facing sections of a roof where moisture lingers. Unlike algae, moss physically lifts shingle edges as it grows, creating gaps that allow water to work underneath.
Both thrive in the damp, cool conditions Missouri saw this spring — and both will keep spreading if left untreated.
Why It's More Than an Eyesore
Moss and algae don't just affect how your roof looks. Over time, they cause real structural damage:
- Granule loss: Algae and moss break down the protective granule layer on asphalt shingles, accelerating wear and reducing UV protection.
- Moisture retention: Moss acts like a sponge, holding water against your shingles and roof decking long after rain stops — leading to rot, mold, and eventually leaks.
- Lifted shingles: As moss grows and dries out through heat cycles, it physically pries shingle edges upward, making them vulnerable to wind damage and water intrusion.
A roof with several good years left can lose that lifespan quickly once moss or algae takes hold.
What NOT to Do
The most common mistake homeowners make is grabbing a pressure washer. High-pressure washing strips granules directly off asphalt shingles — the same granules that protect your roof from UV exposure and weathering. One aggressive cleaning session can cause as much damage as several years of normal wear. Wire brushes and harsh DIY chemical treatments carry the same risk.
What to Do Instead
If you're seeing black streaks, green patches, or fuzzy growth on your roof, the right move is a professional roof inspection. A qualified roofer can assess how far the growth has spread, evaluate whether your shingles have already taken damage, and recommend the right treatment — whether that's a professional soft-wash or shingle replacement in areas of significant damage.
Contact Bridgewater Roofing
The Bridgewater Roofing team serves homeowners across Missouri and the Four-States area. If this spring's wet weather has left its mark on your roof, don't wait for the damage to go deeper.
Contact Bridgewater Roofing today for a professional roof inspection and get a clear picture of what your roof needs before summer is over.