What are zinc strips? Why does my roof have this ugly staining? As a home inspector, I often see roof coverings that have this staining on one or more roof surfaces. So read on to see how zinc strips are used to help prevent this staining from appearing.
Why does the Roof look this way?
The dark staining you see in the above photo is algae. Algae does not like the sun, in fact it’s terrified of the sun. So algae keeps away from the sun by appearing on the North sides of roof surfaces. The North side of roof surfaces see limited sunlight so the staining is worse there. Algae itself does not typically damage a roof so the effects are mostly cosmetic. This is not to be confused with lichen and moss, both of which can impact the integrity of the roof covering.
What are Zinc Strips?
Zinc strips are used to help prevent the formation of algae on roof surfaces. They can be installed after algae has formed, however the results may take some time. Zinc strips release zinc-ions that help clean the roof and limit the growth of algae. After installation, the strips will begin to weather and will appear with a dull color. Typically, they are installed at the ridge of the roof which usually protects up to fifteen feet below the strip. For very long roof rafters, install an additional strip further down the roof. Many manufacturers make these products and all have specific instructions on how to install them. Brands such as Z-Stop and ZincArmor are some of the more popular manufacturers of zinc strips.
Should I have Zinc Strips?
You can see in the above photo how the zinc-ions have been released below the exhaust flue. As a home inspector, I often see conditions such as this and the homeowner believes something is wrong with the roof in the dark areas. In this case, nothing is wrong with the roof. Cosmetically, the roof would certainly be more attractive had zinc strips been used. Other metals such as copper also have anti-algae properties. As a matter of fact, most newer shingles are AR or Algae Resistant. Shingle manufacturers do this to prevent algae growth by placing copper covered granules throughout the shingles. Certainteed, a manufacturer of shingles and other building products, have a technology known as StreakFighter which actually gives a warranty against algae on their shingles.
Conclusion
Algae growth is mostly cosmetic. Using algae resistant shingles is the first step in keeping algae from forming. If you are particularly concerned about algae growth, you should inquire about zinc strips when doing your next roofing project. If your roof is a focal point of the home or is highly visible, you may want to include zinc strips on your next roof. In addition, some other ways exist to clean the roof such as power washing and using chemicals. I would advise against power washing the roof as this can damage the roof if not done very carefully. Different manufacturers exist advertising chemicals that clean roof surfaces. However, some of these chemicals work better than others.
As a home inspector serving Rockford, Illinois, I see algae growth on many roof surfaces. The Lask Inspection Group, LLC feels it’s important to educate and inform home buyers on many aspects of their future home. When you are ready to buy a home, let the Lask Inspection Group, LLC be your ally. Call now to set up your home inspection at 815-978-7785. You can also book your home inspection online by clicking this link.
