How to Kill Roof Moss

It may seem charming on quaint cottages, but roof moss can cause extensive damage to your roof and home. Moss can ruin shingles, degrade the underlying surface and threaten your home's structural integrity. It can even affect your family's health. By being proactive with moss treatment, your can extend your roof's life and protect your family.

With these simple steps, you can kill roof moss and avoid costly home repairs:

Understand Roof Moss and Damage

Cracks and crevices between roof shingles provide ideal spots for moss to grow and spread. These simple plants flourish wherever moisture collects, particularly on north-facing or tree-shaded roofs. Moss doesn't need much light or nutrition, but moisture is crucial. In humid areas prone to foggy mornings and moderate winters, a slight dusting of moss can escalate to a serious roof problem.

Left unchecked, roof moss grows into a thick, resilient layer. Established moss acts like a sponge, soaking in moisture from below and above, and keeping your roof constantly moist. Moss creeps under shingle edges as it spreads, prying shingles loose and letting damaging moisture reach the layers below. Damage progresses from shingles to rotten underlayments and damaged framework. Health-threatening mold can develop and travel down walls to affect living areas as well.

Untreated moss gains a foothold in crevices and cracks as it spreads.

Choose Effective Roof Moss Controls

When treating roof moss, it's important to use effective products designed especially for roofs. Mosses don't function like regular plants, so common weed killers and home remedies don't work — plus they can harm roofs. In the same way, keep products meant to kill lawn moss on lawns, but off your roof. Many of the best lawn moss products contain iron substances, which naturally leave rustlike stains behind. The best roof moss products kill roof mosses quickly and effectively without staining your roof or corroding gutters.

Effective roof moss products work on the same principle as lawn moss controls and prevent moss from retaining water. Without moisture, roof moss dries out, turns dark and dies. Highly effective, non-staining roof moss control products come in easy-to-use dry and liquid formulas:

  • Dry CORRY'S Moss B Ware granules and the micro-granular Lilly Miller Moss Out! Roofs and Structures come in easy, ready-to-use shaker canisters. These zinc-based products kill roof moss without unsightly staining, and they won't corrode galvanized gutters as some moss products do. If preferred, you can mix these dry products with water, according to label instructions, and use them in a liquid form. 
  • Liquid Lilly Miller Moss Out! Roofs & Walks is available as a ready-to-spray formula and an economical concentrate with two convenient sizes for treating small or large roofs. These highly effective moss products rely on ammoniated soap of fatty acids to kill roof moss and algae quickly. You'll see results in hours.

Always follow product label instructions closely, and make sure the label lists your shingle and gutter materials before you treat. Cover any plants right below your roof line during applications. If the products drips down, rinse plants well.

Moss are often concentrated in roof areas shaded by overhanging trees.

Treat and Protect Against Roof Moss

The best time to treat roof moss is when it's actively growing. Moss grows very little in summer, but it kicks into high gear during fall rains, moderate winters and early spring months. Treating right before peak fall rains is perfect timing for roof moss treatments. You'll get the best results if moss is damp, but no rain is forecast for a few days.

If possible, remove excess moss with a rake or broom first. The upper layers of thick moss protect the bottom layer against moss killers. For pitched roofs that you can safely walk, sprinkle dry formulas along the roof ridge. Rains will wash the product down and cover the lower areas for you. For flat roofs or roofs that aren't safe to walk on, use a liquid formula and a pump-style sprayer to cover all the roof surfaces easily.

As moss dies, rains will wash dead moss away. You can speed the process with a broom or rake, too. To be proactive in moss control, treat your roof right before the rainy season each year. Always keep roofs and gutter free from leaves and other debris that can hold moisture in and promote moss growth.

Keeping roofs free from moss helps avoid costly home repairs.

By taking action to kill existing roof moss and prevent its return, you can protect your family and your investment in your home. CORRY'S Moss B Ware and Lilly Miller Moss Out! products help you take control of roof moss, enhance your home's appeal and put an end to roof moss damage and costly repairs.

Lilly Miller and Moss Out! are registered trademarks of Central Garden & Pet Company.

CORRY'S and Moss B Ware are registered trademarks of Matson, LLC.