If you’ve noticed greenish-gray patches creeping across your roof, you’re likely dealing with lichen. It’s not just a cosmetic issue, it can hold moisture against your shingles, cause premature wear, and even void certain roofing warranties if left unchecked.
What Exactly Is Lichen?
Lichen is a slow-growing organism that’s a mix of fungus and algae. It latches onto your shingles, especially in shaded or damp areas, and thrives over time. Once it takes hold, it can be stubborn, resistant to both weather and casual cleaning.
And while it might look harmless at first, lichen traps moisture against the roof’s surface, leading to granule loss and weakening the integrity of your asphalt shingles over time.
Safe Ways to Kill Lichen on Your Roof
Not all cleaning methods are roof-safe. Pressure washers, for example, can strip off your shingle granules and do more harm than good. Instead, here are safer, more effective options:
1. 50/50 Bleach & Water Solution (With Caution)
A mix of household bleach and water can help kill lichen on contact. Here’s how to do it right:
- Mix 1 part bleach to 1 part water in a garden sprayer.
- Spray affected areas and let the solution sit for 15–20 minutes.
- Rinse gently with a hose, no pressure washing!
- Note: Use sparingly, and never let it run off into flower beds or ponds. Always wear gloves and eye protection.
2. Store-Bought Lichen Killers (Zinc- or Copper-Based)
There are commercial roof cleaners specifically designed for moss and lichen removal, often containing zinc sulfate or copper compounds. These are gentler on your shingles than bleach and are usually safe for repeated use.
Look for:
- Wet & Forget Moss, Mold, Mildew & Algae Stain Remover
- Spray & Forget Roof Cleaner
These typically require application and rain to do the rinsing for you over time, making them a low-effort option.
3. Manual Removal (Not Always Recommended)
Using a brush or scraper may seem like a direct fix, but it can seriously damage your shingles if done improperly. If you’re considering this, talk to a roofing professional first. In most cases, a chemical solution is safer.
What Not to Do
- Do not power wash your roof. The high-pressure stream can blast away protective granules and lead to leaks.
- Do not use vinegar, it’s not strong enough to kill lichen and could damage nearby vegetation.
- Do not ignore it. Lichen won’t go away on its own and will only get worse with time.
Long-Term Prevention: How to Keep Lichen from Coming Back
Once you’ve cleaned your roof, here’s how to make sure you don’t have to deal with lichen again any time soon:
Install Zinc or Copper Strips
These strips, installed near the ridge line, release trace amounts of metal ions every time it rains. Those ions create an environment where algae and lichen can’t survive.
A bonus? Some CertainTeed shingle lines, like Landmark® and NorthGate®, already come with copper-infused granules as part of their StreakFighter® technology. Though StreakFighter is mostly geared towards algae-resistance, it does so by being a water-resistant material, something that moss and lichen also need to thrive.
Trim Overhanging Trees
More sunlight = less moisture retention = less lichen. Trimming trees also helps prevent debris buildup, which can trap moisture on your roof.
Keep Gutters Clean
Clogged gutters can lead to standing water along the roofline, giving lichen a cozy place to settle in. A good rule of thumb is to clean your gutters at least twice a year, more often if you’re surrounded by trees.
Regular Roof Maintenance
Schedule annual or bi-annual roof inspections with a professional. Early detection makes treatment easier and can save you from major repairs down the road.
Is It Time To Replace Your Roof?
Call us at 603-838-7663 or request a free estimate. We serve homeowners throughout New Hampshire, Massachusetts, Maine, and Vermont, no mystery fees, no pushy sales people, just honest work done right.
