A new roof is one of the largest maintenance expenses for homeowners. If you are putting on a new roof you will want to make it last as long as possible. Zinc roof strips can be a great solution to prolong the life of your roof and protect it from the destructive consequences of moss and algae infestation.
Moss, algae and fungus growth on roofs is a problem across most of the eastern half of the United States. You may have noticed streaks of discoloration on a roof. On a cedar shingle roof, the black streaking is not a sign of weathering, rather it shows that algae is breaking down the wood shingle.
Lets take a close look at how zinc roof strips can protect your roof and how much they cost.
What is Moss?
Moss consists of a mass of small plants that grow practically anywhere there is shade and water. They are usually yellowish, green, or greenish brown in color, and can appear as small tufts, large mats, or anything in between. Unlike traditional landscape plants, moss does not absorb water through its leaves or roots.
Moss spores may also be carried by wind or animals and can easily spread throughout neighborhoods. Unlike algae, moss can be detrimental to asphalt shingle performance.
Moss tends to grow on north facing roof planes that receive less direct sunlight and stay damp longer than south facing planes. Overhanging tree branches provide additional shade and drop debris on the roof that further holds in moisture and acts as a food source for moss.
Why Is Moss Bad for Your Roof?
Moss growing on your roof needs attention because it can lead to structural damage. As moss grows, it can cause the edges of the roof shingles to curl and lift. This increases the risk of shingles coming loose during strong wind storms.
It also allows water to get underneath the shingles where it can cause rot on the roof deck and potentially create leaks. The moist growing environment keeps the roof surface wet, which encourages mold and bacteria growth that slowly damages your shingles.
Sometimes the damage is so severe that the roof needs to be replaced before its normal lifespan. However, roof repairs can also get expensive, as an average repair call for asphalt shingles runs $450-700.
Cedar-shake roofs are more prone to moss problems than composition asphalt or metal roofs.
The most common place for moss to grow is on the north side of a roof because that is the side that receives less direct sunlight and stays damp longer.
How Zinc Roof Strips Work
Attaching zinc roofing strips to your roof is also effective in preventing the growth of moss. Once you have removed any existing moss on the roof, you can apply the zinc strips.
When it rains, the natural action of rainwater on the zinc strips releases zinc carbonate, a proven fungistat. This washes down the roof preventing future moss, algae and fungus growth.
Average Cost of Zinc Roof Strips
Typically, zinc roof strips together with nails cost about $50-60 for a 50 foot roll. Without nails, zinc roof strips cost $30-35 for a 50 foot roll.
Cost of zinc roof strips by brand
Here is a break down of how much top zinc roof strip brands charge for their products. You can buy many of these on Amazon or at Home Depot.
Preparing a Roof for Zinc Strips
If your roof is new, there is no preparation necessary. If you have an older roof that already has moss, mold or algae, you should remove them before installing zinc strips.
Use a hose to spray the moss with plain water at a downward angle. Then, use a long-handled soft-bristle scrub brush to remove the moss from the roof, scrubbing from the top down to avoid lifting shingles.
As you continue, rub gently – don’t scrape, scour, or pound on the roof. Work in one small section at a time to avoid ripping, cracking, or breaking the shingles.
If this method does not sufficiently remove the mold and moss, there are several commercial products sold and many DIY recipes online.
Just remember that some chemical products may stain siding, decking or pathways so you may need to cover those with heavy sheeting before applying.
Power-washing a roof is not recommended as the force of the jets can damage roofing shingles and remove the shingle granules that protect the roof.
How to Install Zinc Roof Strips
Strips of zinc flashing, or flexible zinc strips which come on 50’ rolls, are placed as close to the roof ridge cap as possible to allow for maximum coverage when the zinc is washed down the roof. The strips are usually placed on both sides of the roof ridge. If the roof has more than one ridge, such as on a hipped-roof or dormer, the strips should be attached on both sides of each ridge.
Starting at one side of a roof, the strip is placed just under the edge of the roofing shingles with the rest of the strip exposed on the top of the row of shingles below.
The zinc strip is nailed into place under the roof shingles using hot-dipped, galvanized roofing nails with neoprene washers. The proper type of nail is important to keep nails from corroding.
The zinc strips are placed next to one another from one side of the roof to the other. It is important not to place them too tightly together to allow for expansion. The process is effective for a distance of about 15 feet below the strips.
If the roof is larger than that, another row of zinc strips should be installed 15 feet below the first row. You can find more information about the proper distance on the packages of roofing strips.
Zinc strips should be also installed below any obstruction that may restrict the rain flow over the zinc and down the roof. This includes chimneys, dormers and skylights.
Pro Tip: Protective eye gear, gloves and work boots should be worn when working with zinc strips. If you are doing this project yourself, do not work alone.
If you do not have experience doing work on a roof, it is better and safer to hire a professional roofer.
Use Hot-Dipped Galvanized Nails to Attach Zinc Strips
Hot-dipped galvanized nails are steel nails that have been immersed in molten zinc at temperatures over 800° F. The temperature is so high that the steel atoms interlock with the zinc atoms creating a zinc alloy that resists rust. The very best quality nails are dipped a second time.
When a roofer tells you that he is using galvanized nails make sure you know the difference between hot-dipped and hot galvanizing. This second process tumbles cold, steel nails in a hot drum. The process does not heat up the steel to produce a zinc alloy but it is cheaper for nail manufacturers.
A third process, electroplating steel nails, makes them look very shiny but they don’t have much zinc on them. Be an informed consumer when making decisions about your house.
How long do zinc roof strips last?
Manufacturers of zinc roof strips claim that the strips will last for 20 years or longer. Superior zinc strips that are made of 99.5% zinc will last longer than those that are zinc-plated, galvanized steel strips.
However, because zinc oxidizes over time, often they stop working effectively in as quickly as 5-8 years. At that point the old strips need to be removed and new ones need to be installed.
Benefits of Using Zinc Strips
– Zinc strips are an effective barrier to moss, algae, lichen and fungus
– Although zinc is harmful to mold and algae, it is not harmful to the plants in your yard.
– Zinc strips can be used on old and new roofs and are effective on all roof materials except Spanish tile roofs.
– Relatively inexpensive. A 50’ roll costs about $30 at home improvement stores.
– Strips come in varying widths depending on area to be covered below installation
– Does not damage roofing shingles
– Can be applied to any roofing material except Spanish tiles.
– Zinc strips should not be used on houses that have copper gutters and downspouts as zinc is corrosive to copper.
– Nailing anything into your roof goes against good roofing practices because of the potential for leaks.
– Zinc strips can warp which can lead to an uneven distribution of the zinc as the rain washes it down on the roof.
– Zinc strips should not be used if your rainwater runoff will mix into a fish pond.
– The rainwater from a roof with zinc strips should not be used to water food crops.
– Removing old zinc strips leaves holes in your roof, which can cause leaks in the future
Alternative Methods to Remove Moss from Your Roof
There are several methods for removing moss from the roof of your house.
Bleach and Water Solution
One method is with a 50:50 mix of liquid laundry chlorine bleach and water. Apply the solution with a sprayer and allow it to stay on the roof surface for 15 to 20 minutes, then rinse thoroughly with low pressure water.
For severe cases, you may need to apply the solution more than once to kill all of the moss. You do have to be careful when using bleach because it can also be corrosive to your roof. Avoid letting the solution dry completely as this may prevent it from washing off completely.
Take proper precautions to protect landscaping and surrounding areas from the bleach. Bleach may stain siding, decking or pathways so you may need to cover those with heavy sheeting before applying. Use appropriate personal protective equipment, as well.
After treatment, the moss will loosen over time and may be removed with a leaf blower. Remember, never use a pressure water to clean your roof.
Water and Scrub Brush
A second method is to spray the moss with water from a hose. Then, use a long-handled, soft-bristle scrub brush to gently scrub from the top of the roof down to avoid lifting shingles. Work in one small section at a time to avoid ripping, cracking or breaking the shingles.
Moss Control Powder
A third way to remove moss is by using a moss control powder. This powder, made of zinc sulfate, is highly effective without posing any threat of roof damage. Only apply the powder to the shady areas of your roof or anywhere you see moss growth. Keep in mind, this powder may be harmful to any animals or vegetation it encounters.
While it may be tempting to power-wash a roof it is not recommended as the force of the jets can damage roofing shingles and remove the shingle granules that protect the roof.
Prevent Moss Growth BEFORE It Becomes a Problem
The most effective way of preventing moss growth on your roof is to trim back overhanging tree branches. These branches provide additional shade which promotes the growth of moss. Leaves and twigs which fall on the roof also provide the right nutrients for moss.
Make sure to keep your gutters clear of leaves and debris, too. When leaves clog your gutters, water overflows onto your roof. Remember, moss grows in moist, shady environments.
I've been a roofer for 15 years, and specialize in Metal Roofing and Flat Roofing.
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