Removing roof moss takes two steps — physical scrubbing with a stiff brush, then applying a cleaning solution to kill remaining spores.
Moss creeping over your roof shingles feels like a losing battle. It starts as a small green patch near a shady gutter and spreads season after season until entire roof slopes look fuzzy.
The good news is that getting rid of moss is straightforward once you know the right technique. The wrong technique — pressure washing — can damage shingles and cost you thousands. This article walks through the safe, effective method that extends your roof’s life rather than shortening it.
Why Moss Thrives On Roofs And What It Costs You
Moss loves roofs that stay damp, shaded, and undisturbed. North-facing slopes, sections under overhanging trees, and low-pitch areas trap moisture long after the rest of the roof dries out.
Moss itself isn’t directly damaging to asphalt shingles in the same way water is. The real problem is that moss holds moisture against the roofing material, keeping it wet for days after rain. That trapped moisture accelerates granule loss on asphalt shingles and can lead to rot on wood shakes.
Moss also gives insects and small animals a foothold on your roof. Once moss thickens, it lifts shingle edges, creating gaps where water can work its way under the protective layer.
Why Scrubbing Beats Spraying
When most homeowners see moss, their first instinct is to grab a pressure washer and blast it off. That instinct causes more roof damage than moss ever would. Physical scrubbing with a brush removes moss without forcing water under shingles or stripping away protective granules.
- Stiff bristle brush or broom: This is the primary tool. A standard scrub brush or a stiff push broom works well on dry or slightly damp moss. Scrub in the direction of the shingles to avoid lifting edges.
- Garden hose with spray nozzle: After scrubbing, rinse loose moss and debris off the roof and into the gutter. Direct the water downward, not upward under shingles.
- Plastic scraper for stubborn patches: Thick, established moss may need gentle scraping before brushing. Use plastic to avoid gouging the shingles.
- Drop cloths and gloves: Moss debris can stain decks and walkways. Lay down tarps below the work area and wear gloves to protect your hands from the cleaning solution.
Pressure washing is not recommended by most roofing professionals. The OSU Extension guide specifically warns that pressure washers can damage asphalt shingles and force moisture deep into the roof structure, leading to leaks months later.
The Two-Step Process For Getting Rid Of Roof Moss
Effective moss removal follows two clear phases. Step one is the physical scrubbing that pulls the visible moss off the surface. Step two is the chemical treatment that kills the microscopic spores and root-like structures left behind.
Per the Oregonstate guide on how to scrub moss off roof, use a standard bristle scrub brush or a stiff broom to physically remove the moss. Do this on a dry day when the moss is crisp rather than slippery.
Choosing The Right Cleaning Solution
After scrubbing, apply a cleaning solution to the affected area and let it sit. This kills any remaining moss tissue and spore residue so regrowth takes much longer. Industry guides recommend pouring the solution directly onto the roof section rather than spraying, to control where it goes and avoid runoff over landscaping.
| Cleaning Solution | Mix Ratio | Notes |
|---|---|---|
| Chlorine bleach + water | 50:50 | Common for asphalt shingles; rinse plants below first |
| Oxygen bleach + water | 50:50 | Safer for landscaping; let sit for 15-20 minutes |
| Sodium hypochlorite solution | 5-6% concentration | Applied as a pre-treatment before scrubbing |
| Zinc sulfate monohydrate spray | Per label instructions | Acts as both a killer and a short-term preventer |
| Commercial moss killer | Per product label | Many contain potassium salts or fatty acids |
Whichever solution you choose, protect nearby plants with plastic sheeting and rinse them with fresh water after the treatment has dried. Bleach runoff can harm garden beds and lawns if not managed carefully.
Step-By-Step Moss Removal You Can Do In A Weekend
You don’t need specialized equipment or professional training to get moss off your roof. The whole process fits into a single Saturday if your roof is accessible and the moss coverage is moderate.
- Clear gutters and trim nearby trees. Remove leaf debris from gutters so you can rinse the roof without clogging the downspouts. Trim back branches that shade the roof — less shade means slower moss regrowth.
- Scrub the moss off the dry roof. Use your stiff brush or broom, working from the ridge down toward the eaves. Brush in the long direction of the shingles, not across them.
- Rinse with a garden hose. Gently spray the loose moss off the roof. Keep the nozzle angled downward so water runs over the shingles rather than under them.
- Apply your cleaning solution. Pour or spray the solution over the scrubbed area. Let it sit for the time recommended on the label — usually 10 to 20 minutes. Do not let it dry on the shingles.
- Rinse again and inspect. Hose the roof thoroughly to remove all cleaning residue. Check for patches you missed and spot-treat them before the solution dries.
If your roof has thick moss layers several inches deep, you may need a second scrubbing pass before applying the solution. The chemicals can’t penetrate a dense moss mat to reach the roofing surface underneath.
Preventing Moss From Coming Back
Killing existing moss is only half the solution. Without prevention, moss will return within a year or two, especially on shaded roof sections. Several methods can extend your moss-free window considerably.
Zinc strips are the most common long-term solution. They attach along the ridge line of the roof, and rain water carries tiny zinc particles down the slope. Those particles create an environment where moss spores can’t establish. The same solution Asphaltroofing recommends in its bleach and water mix guide kills existing moss, while zinc strips handle prevention going forward.
Zinc Strips And Copper Strips
GAF — a major roofing manufacturer — states that zinc strips help control moss and mildew growth but will not remove existing growth. The roof must be cleaned thoroughly before installing the strips. They work on asphalt shingle, wood shake, and tile roofs, though only the roof area below each strip receives protection.
Copper strips are considered a more effective option by some sources, though with a higher material cost. Both metals work through the same rain-wash mechanism, releasing ions that suppress moss and algae growth.
| Prevention Method | How It Works |
|---|---|
| Zinc strips | Rain water carries zinc particles down the roof, suppressing spore growth |
| Copper strips | Same mechanism as zinc, reported to be more effective but more expensive |
| Annual zinc sulfate spray | Reapply once yearly or at first sign of regrowth; won’t stain surrounding surfaces |
| Tree trimming | Reduces shade and moisture on the roof surface |
The Bottom Line
Getting rid of roof moss comes down to scrubbing it off physically, treating the surface with a cleaning solution, then installing prevention like zinc strips or annual sprays. Skip the pressure washer — it’s the fastest way to shorten your roof’s lifespan. Most homeowners can handle the job in a weekend with basic tools from the hardware store.
If your roof is steep, has multiple stories, or you’re not comfortable working at height, a licensed roofing contractor can handle the scrubbing and install zinc strips safely. Pushing moss removal past your comfort zone isn’t worth a fall.
References & Sources
- Oregonstate. “How Remove Moss My Roof” To remove moss, use a standard bristle scrub brush or a stiff broom to physically scrub the moss off the roof surface.
- Asphaltroofing. “Algae Moss Prevention Cleaning Asphalt Roofing Systems” A 50:50 mix of laundry-strength liquid chlorine bleach and water is an effective cleaning solution for killing moss and algae on asphalt roofing.