Why You Shouldn’t Ignore Lichen on Your Roof

At first glance, a few patches of green, yellow, or crusty grey lichen on your roof might seem completely harmless—maybe even a bit rustic. However, unlike standard dirt or dust, lichen is a living organism made up of a fungus and an alga working together. If left untreated, it doesn't just sit on top of your roof; it actively eats away at it.

Here is a breakdown of the damage untreated lichen can do to your home and why addressing it early saves you thousands in the long run.

1. It Eats Away at Roofing Materials

Lichen produces weak acids as part of its natural growth process. While these acids act slowly, over time they chemically break down the minerals in concrete tiles, clay, and asphalt shingles. On metal roofs, trapped moisture and organic acids can strip away protective coatings, paving the way for rust and corrosion.

2. Root-Like Structures Cause Cracking and Pitting

To anchor itself against wind and rain, lichen sends out tiny, root-like filaments called rhizines. These filaments dig deep into the microscopic pores of your roofing materials. As the lichen grows and expands, it widens these pores, causing:

• Pitting and flaking on concrete and terracotta tiles.
• Granule loss on asphalt shingles, which strips away their UV protection.
• Micro-cracks that compromise the structural integrity of the tile or shingle.

3. Trapped Moisture Leads to Leaks and Rot

Lichen acts like a dense sponge, holding onto rainwater long after the sun comes out. Keeping your roof constantly damp accelerates wear and tear. Worse, in colder climates, that trapped water freezes and expands overnight. This freeze-thaw cycle forces small cracks open wider, eventually allowing water to seep beneath the roofing material and rot the timber framing and underlayment below.

4. Blocked Gutters and Drainage Issues

As lichen matures, chunks of it break off during heavy rain or windstorms. These clumps wash down into your gutters and downpipes, creating stubborn blockages. Blocked gutters cause water to overflow, which can damage your fascia boards, flood your eaves, and even pool around your home’s foundation.

5. Reduced Energy Efficiency and Street Appeal

A roof covered in dark, crusty lichen absorbs more heat than a clean, reflective surface, making your home warmer in the summer and driving up cooling costs. On top of that, a heavily stained roof drastically hurts your home’s street appeal and can lower its property value—or even void your roofing manufacturer's warranty if regular maintenance is neglected.

What You Should (and Shouldn't) Do

If you spot lichen taking over your roof, resist the urge to grab a high-pressure water blaster. High-pressure washing will blast away the protective surface of tiles, strip paint from metal roofs, and force water underneath your roofline.

Instead, opt for a soft-wash treatment. Biodegradable moss and lichen treatments gently kill the organism at the root without damaging your roof, allowing wind and rain to naturally wash the dead lichen away over the following months.