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How do Zinc Strips Work?

For decades, zinc strips have been used to keep moss from growing on roofs. This is an explanation of how they work and how they are installed. It also explains the limitations of zinc strip, from the point of view of good roofing practices and experience.

Zinc strips work when rain rolls over the metal in the strip, and tiny metal particles are carried down the roof. The metal is poisonous to algae, moss, lichen, fungus, mold and other simple plant life, all of which stain, look bad, and are unhealthy for your roof. The moss that’s growing will gradually wither, die and fall off, and so should stains and other simple plant life organisms, when everything is working properly. It should also keep the moss away for five years or so.

In order to have the rainwater run over zinc strips and evenly treat the entire roof with leaching metal, the strips of zinc need to be installed, first, under all ridge cap, whether straight or angular (hip). Since the process is effective for about 15 feet, there needs to be another line of zinc strip installed 15 feet further down the roof. If there is enough zinc for the raindrops to run over, in the right places, and all are flat and even on the roof, complete freedom from moss for five years should happen.

What can go wrong with zinc strips?

Firstly, nailing the zinc strip onto roofing does not follow good roofing practices. Exposed nail heads leak when the nails work themselves out gradually, because the gap allows water to wick inward. Expansion and contraction causes this. Self-sealing screws would need to be used, adding to the expense.

zinc strip illustration 1
Secondly, the zinc strip sold in hardware stores is thin, and this allows for warping of the metal. When not lying absolutely flat, the metal will not allow water to flow directly over and downward, as it should if it is to do its job and kill the moss. Instead of running over, the water runs along the strip until it finds a flatter area, and a stream of really great zinc flows there, doing a wonderful job under the stream. The part of the roof under the warped strip is not being treated and will allow moss to grow.

zinc strip
Thirdly, the zinc strip oxidizes over time, so that in five years or so, the effectiveness is over. You must then remove the old zinc strip and install a new one, leaving many nail holes.
Fourthly, the thin zinc strip breaks as a result of wind causing metal stress. Then you have metal clanking around on the roofing material. Ineffective and ugly.

zinc strip falling off
Fifthly, let’s look at the appearance of a medium sized modern Hip and Valley roof which has zinc strips installed properly. Sixth, let’s consider the cost of all that metal, plus the labour of installing and re-installing the strips.

zinc strip illustration 2

Seventh, leaching metals are toxic to fish. The harm the environment.

Eighth, there are many failures to actually kill roof moss and keep it away.

zinc strip that isn't protecting a roof moss growing on a roof despite zinc strips

The ROTban REVolution solves all these problems

Firstly, we use no nails, nor do we create much traffic on the roof. ROTban is applied with a gentle liquid treatment spray that bonds to the roof’s surface.

Secondly, since the product bonds to roofing, water will not in any way be hampered from flowing directly downward.

Thirdly, ROTban does run out in 5 years, but the re-application is not damaging to the roof.

Fourthly, there is nothing to break.

Fifthly, ROTban is not visible on your roof. The cleaning process is all you see.

Sixth, ROTban costs no more than a proper zinc strip installation.

Seventh, ROTban is not harmful to the environment.

Eighth, when a zinc strip fails in some way, what do you do about it? Go up there yourself and fix it? Do you know all about fall protection? Is there a company that will guarantee it effective? Will they fix it free? ROTban is applied with complete safety to your roof and the workers. It is effective for years, a proven fact over decades of time. ROTban Structural Services Corp stands fully behind the effectiveness of our treatment with a follow-up inspection and free warranty service for Four Years.

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