Heritage Restoration, Inc.

Roof Cleaning

How do I clean lichen or moss off a roof?

 

What you will need:

Project buddy

Ladder and Safety Equipment, like a harness

2-gallon bucket

Quality Pump Sprayer

Stiff bristle brush with pole attachment

Cleaner

Water

Hose w/ nozzle and/or power washer

 

Prep

Make sure someone else is around.  You may need a hand with a ladder or to just be there if you need help, like a phone call.

 

Cover vegetation with plastic or a tarp.

 

Use a properly sized ladder to access the roof.  Use a ladder standoff at the top of the extension ladder to lean against the roof, not the gutter.  The ladder should extend one to three feet above the roof edge.  The angle should be about 75-1/2 degrees in relation to the ground.  There typically is an “L” image on the side of the ladder where the “L” is meant to be vertical when properly set.  Use the adjustable feet to get the ladder set vertically.  Do not use the half of the extension ladder without the feet, since it will slide out.  Lift the ladder off the building to be sure it is stable side to side.  If it is not, adjust the feet or put a wood wedge under the foot.  When a ladder is properly set, it will not slide side to side, especially if you are not performing any Olympic feats at the top.

 

A stepladder should be about 1 foot taller than the roof.  Do not use the top step of a stepladder, since the ladder becomes unstable.

 

If you are planning on climbing on the roof, you should really wear a harness.  A properly set harness gives you the piece of mind that you will live through the project.

 

Get a good quality garden pump sprayer to apply the cleaner.  There are power washers that can mix, although you want the cleaner to be absorbed and break the bond of the moss or lichen first before you scrub it.

 

Cleaners

Hydrogen Peroxide cleaners

Mix an equal part food grade 35% hydrogen peroxide cleaner with warm water.  Hydrogen peroxide is a non-toxic, anti-bacterial, anti-fungal, anti-mold and anti-mildew. It can be bought in bulk concentrated form, making it fairly inexpensive.

 

Distilled White Vinegar

Vinegar has been around for centuries.  White vinegar is a natural source of distilled acetic acid.  Vinegar is said to provide many heath benefits, from certain mineral absorption to preventing diseases.  There are thousands of ways to use vinegar in cleaning or to control organic growth.  We have used it straight up in a pump sprayer to kill weeds and mildew (I also use a weed torch for masonry patios and walkways; it is effective and way cool).

 

Pour distilled white vinegar into a bucket. The vinegar should not be more than 5 percent acetic acid strength. Add one1 oz. of dish soap to help the vinegar cling to the moss and lichens.

 

Bleach

Bleach is not my first choice since it can be harmful to plants and the environment, burns your skin, and it has a smell that sticks to you. But that is why it is good for killing moss and lichen.

 

Mix a solution of equal parts chlorine bleach and warm water into a sprayer.
Premixed Cleaners

Acetic Acid, or vinegar, and Sodium O-Phenylphenate, fungicide used in food, based cleaners can be mixed with household bleach.  They are less harmful to vegetation, although can be an irritant to people in confined spaces or on your skin.

 

There are also flashy products all in one products that contain “proprietary blends of Cationic Surfactants and Isopropyl Alcohol”, two things not particularly friendly to the environment.  There is no need to use these products, especially with other natural alternatives.

 

Process

Brush off the loose moss with a stiff bristle brush or broom.  Brush in a downward direction, so you do not lift off any shingles.  If the shingles are too vulnerable and brittle, skip to the treatment wash.

 

Apply the cleaner to the roof when it is cool and not in direct sunlight.

 

Let the product sit for about 30 minutes.  Do not let the product stay on longer, since it can degrade the roof.

 

Wash off cleaner with a light power wash or a light powered hose from the top down, which gets dangerous. Do not saturate the roof or use the power of the wash to take off the vegetation.  It can damage the roof or make shingles fall off.

 

Maintenance

You can use zinc or copper strips at the top of the roof to kill any organic growth.  Keep the roof clean and free of debris as much as possible.  Do not leave moss or lichen for too long, since it will shorten the life of the roof, and cost you more to replace it than clean it.

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