What’s Growing On My Roof?

Unsightly and potentially damaging, moss growth on roofs is a maintenance problem common to homeowners all across America. Moss has tiny roots that trap dirt and debris and hold moisture in contact with the roofing material. Moss build-up can deform shingles and accelerate decomposition, causing leaks and deformed shingles that can blow in the wind. Regular applications of herbicide will kill moss and prevent expensive roof repairs.

Controlling Moss With Herbicides

Prior to applying herbicides, clean the roof to remove dirt and debris. Sweep the roof or use a scrapper on a long pole. Always start at the top of the roof and work down. Do not push upwards against the shingles as this may cause damage and lift or loosen the components of the roof. Cleaning your roof is a dangerous job. It is easy to slip and fall. Always work from a dry area and wear shoes with excellent traction. Safety harness should be employed.

Moss can be controlled with products containing Ferrous Ammonium Sulfate or Iron Sulfate. An effective mixture is 3 ounces of Iron Sulfate in 5 gallons of water. Apply the mixture on the moss infected area. 5 gallons will cover approximately 1000 square feet. Apply with an airless sprayer, hand sprayer or cotton mop. Several commercial products containing Ferrous Ammonium Sulfate or Iron Sulfate are available for purchase from hardware stores or home and garden centers. Follow manufactures instructions for application. (Keep Iron Sulfate spray away from foundations and concrete patios. The iron will stain concrete.)

Many states have strict regulations that cover the purchase and application of herbicides that will effectively kill moss. For safe application, employ the services of a licensed roofing repair and maintenance firm.

To achieve optimum results, apply herbicides on a dry roof. Herbicide should be applied in the spring or summer when moss is in a growing cycle. Choose a time when dry weather is predicted for several days. Temperature significantly impacts efficacy; do not apply when the roof temperature exceeds 85 degrees F. After applying the herbicide to the roof, be sure to clean out the rain gutters. Herbicide trapped in the gutters will cause the gutters to rust and reduce the useful life of the gutters.

Roof moss should be treated every three years or as required to control growth. Moss flourishes in shade and on sections of the roof that have a northern exposure. Pay close attention to these areas to avert serious roof damage.