How to Remove Moss From a Roof

Moss looks soft and harmless, but it traps water against your roof. Over time that moisture can shorten the life of shingles, cause leaks, and overload gutters. Moss grows fastest on cool, shaded, damp roof areas, especially under trees and on north-facing slopes. That’s why you often see the worst build-up beneath big evergreens and on the north side of a house.

Before you start: safety first

Roofs are slippery when wet and even more so where moss grows. Use basic fall-prevention habits every time you leave the ladder.

• Wear shoes or boots with good grip.

• Work when the roof is dry and winds are calm.

• Keep your body below your feet; don’t lean downhill.

• Use a roof harness and rope if slopes are steep or the ground below is hazardous.

• Never pressure-wash asphalt shingles; it can strip protective granules and shorten roof life. Use chemical cleaning and gentle tools instead.

Why moss grows (and why it’s a problem)

• Shade + moisture. Moss thrives where the sun struggles to reach and surfaces stay damp—under trees and on north-facing planes. House Beautiful+1

• Debris = food + sponge. Needles, leaves, and silt hold moisture and feed growth, creating a wet mat that can push up shingles and disrupt drainage.

Left alone, moss holds water against the roof, can lift shingle edges, and contributes to leaks and wood decay. Routine cleaning and a light chemical treatment are the simplest long-term fix.

Tools and materials

Tools

• Nylon bristle brush on a long pole

• Leaf blower (or soft broom)

• Hand pruners or pole saw for small branches

• Ladder with stabilizer

• Bucket, gloves, eye protection

Materials

• Oxygen-based cleaner (sodium percarbonate) or soft-wash solution (dilute sodium hypochlorite)

• Garden sprayer or sprinkling can

• Clean water for pre-wetting plants

• Trash bags for debris

Step 1: Loosen and remove the bulk of the moss

1. Work dry when you can. Dry moss sheds more cleanly.

2. Use a nylon brush. Start at the top edge of a patch and gently push downhill. Do not scrub hard across the surface; the goal is to remove thick pads, not scour the roof.

3. Use a “stick method” on stubborn clumps. Slide a wooden paint stirrer or dull stick under the moss to lift it, then brush away. This avoids heavy friction on the shingle surface.

4. Don’t chase every speck. The treatment phase will kill remaining fragments. Over-brushing risks damaging the shingle granules.

Step 2: Tidy the surface and clean the gutters

• Blow or sweep loose debris (needles, leaves, moss crumbs) from the roof so it can drain correctly.

• Clear gutters and downspouts. Debris here causes overflows that keep edges of the roof wet and invite more moss. Make sure downspouts run freely. Prime Solutions+1

• Optional: Rinse skylight glass by hand if it’s dirty and safe to reach

Step 3: Trim back branches that shade the roof

Trim small limbs that hang over the roof to let in more sun and reduce future debris. More light and airflow mean a drier roof, and a drier roof is less friendly to moss.

Step 4: Choose a treatment method

You have two common, effective choices. Pick the one you can apply safely and correctly.

Option A: Oxygen-based cleaner (sodium percarbonate)

• Often sold as an “oxygen bleach.” When mixed with water, it releases hydrogen peroxide and soda ash to raise pH and oxidize organic growth.

• Favored by many for being plant-friendlier when used properly and for not requiring pressure.

How to apply

1. Pre-wet nearby plants with clean water.

2. Mix per label in a sprayer or watering can.

3. Saturate mossy areas and adjacent shingles.

4. Dwell time: Let it work per product directions.

5. No heavy rinsing needed; remaining dead residues weather off with rain.

Option B: Soft-wash bleach solution (sodium hypochlorite)

• Industry groups representing asphalt shingle makers recommend dilute bleach solutions for algae and moss, without pressure washing.

How to apply

1. Protect landscaping by pre-wetting plants and soil.

2. Mix per guidance (see manufacturer or ARMA recommendations) and apply evenly with a low-pressure sprayer.

3. Allow proper dwell time so it kills the growth.

4. Light rinse if directed, keeping runoff minimal.

Important: Don’t rely on a pressure washer to “do the cleaning.” Chemical kill is the method; pressure risks shingle damage.

Why not pressure wash?

Even “lower” pressures can strip shingle granules and reduce roof life. Most roofing bodies and manufacturers discourage using pressure washers on asphalt shingles. Use chemical soft-washing and gentle tools instead.

Step 5: Inspect water movement

After treatment and clean-up:

• Check that water drains freely to gutters and downspouts.

• Confirm there’s no ponding behind debris piles or at valleys.

• Look for lifted shingle edges that might need a roofer’s attention.

Clog-free gutters and clear paths are a big part of preventing leaks and recurrent moss.

Step 6: Plan your maintenance rhythm

How often you need to re-treat depends on shade, trees, and local climate.

• Heavy shade + trees: inspect every 6 months; expect annual touch-ups.

• Mixed exposure: once a year is often fine.

• Open, sunny roofs: inspect yearly; treat as needed.

Routine checks, debris removal, and clear gutters cut down on moisture and delay new growth.

Extra prevention ideas

• Metal strips at the ridge. Zinc or copper strips can reduce regrowth as rain releases trace metals onto the roof surface. (Consider aesthetics and local runoff rules.)

• Ventilation. Adequate attic ventilation helps keep the deck drier.

• Choose algae-resistant shingles next time you reroof; many include copper-infused granules.

Simple checklist

Safety

•  Stable ladder with standoff

•  Grippy shoes, gloves, eye protection

•  Dry, calm weather

•  Harness/rope on steep or high roofs

Clean & prep

•  Gently brush off thick moss

•  Blow/sweep remaining debris

•  Clear gutters and downspouts

•  Trim small branches shading roof

Treat

•  Oxygen-based cleaner or soft-wash bleach (never pressure wash)

•  Pre-wet plants; protect surfaces

•  Apply evenly; allow dwell time

•  Light rinse only if directed

Aftercare

•  Confirm free drainage

•  Bag debris; tidy ground

•  Set inspection reminder (6–12 months)

Frequently asked questions

Will moss die if I just leave a powder on the roof and wait for rain?

Yes, many oxygen-based powders activate with moisture. Follow the label and expect results over days to weeks as residues weather away. Wikipedia

Is bleach safe for my shingles?

Dilute sodium hypochlorite, applied as a soft-wash and rinsed appropriately, is the method recommended by asphalt roofing groups for organic staining—provided you avoid pressure and follow directions. Protect landscaping.

Can I pressure wash a tile, cedar, or metal roof?

Pressure can damage many roofing materials or drive water under laps. Use appropriate chemistry and low pressure. When in doubt, ask the roof manufacturer or a qualified roofer.

What about gutters—are they really part of moss control?

Yes. Clean gutters and clear downspouts keep roof edges dry and reduce moisture that supports moss growth. Guards can help, but still plan periodic checks.

Key takeaways

• Moss thrives in shade + moisture and feeds on debris. Keep the roof clean and the trees trimmed.

• Brush gently to remove bulk growth; don’t scour the granules off shingles.

• Treat chemically with oxygen-based cleaners or soft-wash bleach—never pressure wash asphalt shingles.

• Gutters matter. Keep them clear so edges dry between storms.

• Repeat light maintenance beats big, risky cleanups.

Sources and further reading

• Asphalt Roofing Manufacturers Association (ARMA): Algae & Moss Prevention and Cleaning for Asphalt Roofing Systems — method and “no pressure washing” guidance.

• Roof cleaning overview and soft-wash description. Wikipedia

• Moss risks and prevention (shade, debris, copper/zinc) — homeowner explainer.

• Manufacturer guidance on avoiding pressure washing and preserving granules.

• Gutter maintenance practices and benefits of guards/mesh.