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What Is the Mixture of Bleach to Water to Kill Moss?

Julie Christensen

In damp climates, moss grows on any surface, including trees, roofs, patios and walls. In natural settings, moss acts as a mulch, conserving moisture in the soil, but moss can damage roofs and patios. Damp moss becomes very slippery, causing unsafe conditions on patios and brick surfaces.

Remove moss by scrubbing it with a chlorine bleach solution or using a commercial moss removal product.

Chlorine Bleach

Mix 1 part chlorine bleach with 9 parts water in a bucket. Do not add vinegar or ammonia, which will create toxic fumes when mixed with bleach. Wear rubber gloves to avoid skin irritation. Apply the solution with a stiff brush, and rinse thoroughly.


Chlorine bleach solutions are most effective when moss is actively growing. Apply the bleach solution to an inconspicuous area first, especially on brick. Wait 24 hours to make sure the bleach doesn't alter the appearance of the surface before you proceed cleaning the rest of the area. Wear eye protection to avoid eye irritation.

Other Solutions

A power washer quickly removes moss, but point the nozzle at an angle, rather than directly at the surface, and set the pressure to no more than 3,000 psi to avoid damage. Use commercial moss cleaners carefully because they can damage or kill plants, and apply them on a dry, windless day. Do not use salt to remove moss. It is ineffective and corrodes metal surfaces.


Cut back trees and shrubs that overhang roofs and patios. Exposure to sun and air is the best way to minimize moss growth. Space plants so air circulates freely between them, which not only minimizes moss growth, but reduces the risk of fungal diseases.