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How to Stop Moss From Growing on House Siding

Moss growing on the sides of houses is a common problem in the U.S. Pacific Northwest and South, but can affect any house in any area where conditions are moist. Moss left to grow on house sides and roofs continue to gain bulk as it spreads and can pry siding or shingles loose. Moss grows from rhizomes that work hard to find dirt in the houses' sides and work their root system into crevices to flourish--and potentially cause expensive damage.

Mix 3 pounds of powdered zinc sulphate monohydrate with 5 gallons of water in a handheld sprayer. Spray the entire area of moss infestation. This mixture will easily cover 600 square feet of house side. The moss will die over several days. Use zinc sulphate monohydrate annually to keep moss from growing on house siding or roofing.

Kill and prevent moss on house sides and roofs by applying zinc chloride in a handheld sprayer. Do not use zinc chloride on painted surfaces or damage may occur. Zinc chloride is ideal for aluminum siding, vinyl siding and roofs. Zinc chloride can be used instead of zinc sulphate monohydrate because it is considered a long term prevention treatment. It can prevent moss regrowth for up to five years on house sides.

The chemical can be purchased as a 13% mixture or as a 62% mixture. Apply the 13% mixture directly to the moss and house sides to kill the moss and prevent regrowth for five years. Hold the sprayer's nozzle 6 inches away from the house side and thoroughly saturate. To use the zinc chloride that is 62% concentrate, mix with water at a ratio of one pint of concentrate to three gallons of water. This mixture will cover 100 square feet of house siding. Apply the same way as the 13% concentrate.

Apply chlorine bleach if you are worried about using harmful chemicals around plant life. Chlorine bleach is less toxic to plant life then zinc chloride or zinc sulphate monohydrate. Apply chlorine bleach to house siding that is painted, or places where you are concerned about staining.

Chlorine bleach will prevent moss regrowth for up to one year, and is also non-corrosive when applied correctly. Mix the chlorine bleach in a sprayer at a ratio of 50% bleach with 50% water. When applying chlorine bleach and water mixture to wood siding, leave on the wood for 15 minutes and then thoroughly rinse with water using a garden hose. Vinyl and aluminum siding require the chlorine bleach and water to be left on for only 30 seconds before hosing off with water.

Purchase rolls of zinc plating. Unroll the zinc plating and measure for application under eaves and around windows. Zinc plating can be nailed along the eves of a house or under windows to prevent moss growth. Nail thin strips along the eves. When seasonal rains occur the zinc leaches from the zinc plating to roll down the house sides and prevent moss growth. This prevention method has been popular for many years.

Another available product, which is similar to zinc plating, called galvanized flashing. It is applied and purchased like zinc plating. Both methods have been effective for a decade or more. Use these methods of prevention once all moss has been removed from the house sides.

Cut back any plants or foliage that touch the house sides using lopers or handheld bypass shears. Foliage touching the house sides can help moss spread.


Spray chemicals on a calm day when there is no wind.

Hose all plants off that come into contact with the chlorine bleach and water mixture. Plants may suffer foliage burn if the mixture stays on foliage for longer than 10 minutes.


Zinc sulphate monohydrate is toxic to all fish and aquatic life. Never use near water.

Zinc sulphate monohydrate can damage plants. Drape all plants to protect with plastic.

Zinc chloride is toxic to fish and aquatic life. Never use near water.

Zinc chloride can damage plants and lawns. Drape plant life with plastic when using.

Zinc chloride is corrosive so do not use around copper piping.

Chlorine bleach is toxic to fish and aquatic life. Never use near water.

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