Concord Carpenter

Removing Roof Moss

By Robert Robillard on Home Maintenance

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Keeping Moss Off Your Roof

I love Moss in the woods, but NOT on a roof. Roof Moss tends to grow on north facing roofs that receive less direct sunlight and stay damp longer than south facing roofs. South facing roofs have the benefit of more sunlight and tend to be drier.

Moss needs a moist environment to survive. There are three contributing culprits that promote the growth of Moss.

• Moisture
• Lack of sunlight
• Roof debris

Overhanging tree branches provide shade, as well as, drop debris onto roofs. The debris help to hold in moisture and acts as a food source for Moss.

Can Moss Damage Your Shingles?

Yes it can! Moss can beat up your shingles  over time and reduce their overall longevity and performance. As the Moss grows it attaches to the shingles, lifting the leading edges of the shingles. As the shingles lift or curl upward they are at an increased risk of tearing off due to high winds.

Roof Safety

I’d be remise if I didn’t tell you that falls account for many serious injuries and deaths in construction. Make sure you take appropriate steps to minimize your risk of slipping and falling. Some of these include:

• Never work on a wet roof.
• Keep your work area as clean of dirt, tools, and debris as possible.
• Wear safe footwear—soft-soled boots provide the best roof traction.
• When working on a steeply pitched roof, protect yourself with safety equipment such as a fall arrest  harness and rope.
• Set up and climb your ladder properly.
• Always wear a helmet to protect your head and prevent more serious injury if you fall.

Check out my article on Ladder Safety Tips and also my checklist at:  Ladder Safety

Removing Roof Moss

There are a bunch of cleaning products for removing roof moss, that allow you to spray and forget. [In fact, I think that is a brand name]  The most effective method I’ve seen for cleaning algae and moss from a roof is with a 50:50 mix of laundry strength liquid chlorine bleach and water. See below.

DIY Roof Moss Remover

If you’re the type of person who like to do things yourself then try this cleaning method. It takes some time to work.   The roof moss will loosen over time and may be removed with a leaf blower, remember to direct the blowers airflow down the slope to avoid driving debris under the edges of the shingles.

Here’s how remove roof moss:

1. Apply with a sprayer and allow the solution to soak in for 15 to 20 minutes
2. Rinse thoroughly with low pressure water
3. You may need to reapply and leave on longer but avoid letting the solution dry completely
4. Remember to protect landscaping below the roof run off and to wear personal protective equipment when working with chlorine bleach.
5. Never use a pressure washer to clean an asphalt shingle roof as this will cause granule loss and very likely premature failure of the roof system.

In severe cases, it may take more than one bleach treatment to kill all of the moss.

Preventative Measures to Eradicate Roof Moss

If you want to be more proactive there are some additional things you can do to discourage Moss growth, there are some steps that can be taken to discourage moss and algae growth:

1. Trim tree branches back to allow more sunlight to reach the roof
2. Reduce debris accumulation on your roof – I see this a lot on low slope [low pitch] roofs. Leaves and branches tend not to blow off. Use a leaf blower to clean the roof, direct the airflow down the slope to avoid driving debris under the edges of the shingles.
3. Keep gutters clean to promote water drainage.
4. Do not allow gutters from an upper roof to drain directly on a lower roof; extend the downspout from the upper roof into the lower gutter.
5. Add zinc or copper strips to prevent both algae and moss, or applying asphalt shingles that incorporate algae resistant copper granules.

Zinc and Copper Strips

As the rain water hits the strips copper or zinc leaches from the strip and kills or retards the growh of the moss. These strips are effective up to 15-feet below and for larger roofs – add a strip midway down or as needed. These strips can control moss for decades.

If you don’t believe this – just look at any house that has a chimney and moss. Typically there will be NO moss growth under the chimney due to the lead flashing at the bottom of the chimney.

Purchase ZincShield Strips Here:

ZincShield-Strip-Stains-Fungus-Mildew

Algae Resistant Shingles

When you reroof you can purchase and install algae resistant shingles. These shingles look like normal shingles but have copper granules embedded thorough out the entire shingle.

The entire roof system works to kill mold and algea, which results in a uniform cleaning and color fade over time. The active ingredient in many of these shingles is called Titanium Dioxide.

There’s not a big uncharge in price for these either.

How to Remove Roof Moss Video