Zinc and Copper Strips and Algae Resistant Shingles: What Works on a Lafayette Roof

Black streaks come back on Lafayette roofs faster than most homeowners expect. You clean the roof, enjoy the fresh look for a while, and then dark lines creep down from the ridge again. That is why so many people start asking about zinc and copper strips and algae resistant shingles. Both promise to keep the growth away.

Here is the short version. Algae resistant shingles are the best long term prevention, but you can only get them when you replace the roof. Zinc and copper strips can slow growth on the roof area below them, yet the Asphalt Roofing Manufacturers Association (ARMA) does not recommend adding them to an existing roof. If your roof is already on the house, a soft wash, tree trimming, and steady upkeep do the job.

Why Lafayette Roofs Grow Algae So Easily

ARMA says algae discoloration is most widespread in the Gulf States and in warm, humid regions. That describes us. NOAA’s 1991 to 2020 normals for Lafayette Regional Airport show about 62.8 inches of rain a year, with measurable rain on about 117 days. July alone averages 14 rainy days.

Live oaks add shade, and north facing slopes dry slowest. Algae spores travel on the wind, so it is common to see streaks across a whole neighborhood. ARMA also notes that by the time algae is visible, it has likely been there for several months or longer.

Algae and Moss Are Not the Same Problem

This matters, because the fix depends on which one you have.

• Algae makes the dark brown or black streaks. ARMA says there is no scientific evidence that algae damages asphalt shingles. It mainly hurts looks.
• Moss is raised and fuzzy. ARMA says moss can lift or curl shingle edges, which raises the risk of wind blow off. In severe cases it can push water sideways and cause moisture damage to the roof deck or leaks.

If you are not sure what is growing on your roof, our guide to roof cleaning in Lafayette shows what each one looks like.

How Zinc and Copper Strips Work

A strip is a thin band of zinc or copper metal. An installer tucks it under the row of shingles closest to the ridge and leaves about an inch showing, according to This Old House. When rain hits the exposed metal, it washes tiny amounts of metal ions down the roof. Those ions make it hard for algae and moss to get started.

What the Strips Protect

Strips only work where rainwater flows over the metal and then across the roof. Installer guides say this plainly. Anything the water does not reach stays unprotected. A long slope, a shaded north side, or a roof broken up by valleys may need more thought than a simple ridge line.

What Strips Cannot Do

Strips do not clean anything. They prevent new growth, but they leave existing stains and moss in place. Every source I reviewed says the same thing: clean the roof first, then think about prevention. For a streaked roof, that means a gentle soft wash, not a pressure washer.

What ARMA Says About Adding Strips to an Existing Roof

This is the part most online guides skip.

ARMA does not recommend adding zinc or copper strips to an existing roof. To slide a strip under shingles that are already installed, a crew has two choices. They can nail the strip with exposed nails, which can cause leaks over time. Or they can break the sealant bond on the shingles, which may eventually lead to wind damage.

ARMA’s advice in plain words: strips belong on a new roof, where they go in during installation, not on an old roof as an add on.

Hurricane season in Louisiana runs June 1 to November 30, according to the National Hurricane Center. A broken shingle seal is the last thing you want going into that stretch. For most Lafayette homeowners with an existing roof, skipping the strips is the safer call.

Zinc or Copper: Which Strip Is Better?

If strips are going on a new roof, the choice comes down to cost and what is downstream of them. One 2026 installer guide sums it up like this. Copper tends to give stronger, longer lasting protection, but the runoff can stain some light colored materials and can corrode metals that sit below it. Zinc usually costs less and often pairs more easily with aluminum drainage, though compatibility still needs checking.

Factor	Zinc strips	Copper strips
Usual cost	Lower	Higher
Strength of protection	Good	Generally stronger
Main concern	Thin stock can bend or wear out	Runoff staining and corrosion of other metals
Next to aluminum gutters	Often easier, but confirm	Needs a compatibility check

Whichever you choose, ask the installer to check what metals the runoff will touch. That includes aluminum gutters and any coated steel.

How Algae Resistant Shingles Work

Manufacturers mix granules that contain copper into the shingle surface at the factory. When the roof gets wet, those granules slowly release copper ions that make it hard for algae to take hold. Patent filings describe copper granules making up about 1 percent to 15 percent of the mix, with 8 to 10 percent by weight the most common.

ARMA says shingles with this technology are available today and that they may be used when it is time to replace a roof. In Lafayette, with our humidity and shade, that is worth a serious look.

There are no extra holes, no exposed nails, and no broken seals. The protection is part of the shingle.

Read the Warranty Fine Print

Algae resistant does not mean algae proof. The warranty tells you what the maker will actually stand behind.

• It covers blue green algae only. Roof warranty guides note that these warranties do not cover moss or other types of growth.
• The label matters. GAF says its 25 year StainGuard Plus warranty applies only to products in packages bearing the StainGuard Plus logo. GAF also offers a 30 year version on Timberline UHDZ shingles. Its warranty includes GAF shingles, hip and ridge caps, and starter strips.
• Other brands vary by line and tier. One analysis of the published documents found that Owens Corning’s term depends on qualifying hip and ridge shingles, with 25 years in one case and 10 in the other. CertainTeed’s runs 10, 25, or 30 years depending on the product.
• Early years can be generous. The same analysis found that several brands have a 10 year period where a valid claim can cover cleaning labor and sometimes replacement.

Brand	Technology	Published term	What to check
GAF	StainGuard Plus	25 years, 30 on the PRO tier	Logo on the package
Owens Corning	StreakGuard	10 to 25 years	Matching hip and ridge shingles
CertainTeed	StreakFighter	10 to 30 years	Product line and tier

Warranty terms change. Read the maker’s current document for the exact shingle line before you sign anything.

What It Costs

One 2026 guide puts the price difference at zero to 8 percent more than standard shingles. Ask your roofer for both prices. Then compare the extra cost with what you would pay for repeat cleanings over the next ten years. Our price ranges are on our soft washing page.

Runoff and Gutters: The Side Effects

Copper and zinc do their job by washing off the roof, so some of it ends up in the water. The Washington State Stormwater Center notes that copper and zinc compounds are toxic to aquatic life. A 2019 study posted by Washington State University’s rural stormwater program measured copper in runoff from algae resistant shingles over 4.5 years and found the granules released it at a steady rate. A 2022 review in the journal Water found that copper and zinc washing off copper and zinc roofing is mostly dissolved and available to living things.

For a single house, the amounts are small. Still, in Lafayette, runoff moves through coulees toward the Vermilion River, so it is fair to know what your roof is adding. If you have aluminum gutters, ask your roofer whether copper runoff will land on them. Our gutter cleaning crews see how fast neglected gutters fill with granules and debris, which makes drainage worse.

Which Option Fits Your Roof

Your situation	Best move	Why
Existing roof with black streaks	Soft wash, then trim branches	This is the method ARMA describes, and strips are not recommended on an existing roof
Existing roof with moss	Treat the moss and check shingle edges	Moss can lift shingles, and strips do not remove it
Roof near replacement age	Choose algae resistant shingles	The protection is built in at the factory
New algae resistant roof with streaks	Read the warranty and call the maker before you pay for cleaning	A claim may cover it
Metal roof	Ask the installer before adding any zinc or copper	Mixing metals can cause corrosion
Old roof and hurricane worries	Get a roof inspection first	Wind safety comes before looks

If your roof is old, the Louisiana Department of Insurance runs the Fortify Homes Program. It offers grants up to $10,000 to eligible homeowners to upgrade roofs to the FORTIFIED standard, and Lafayette Parish is on its list. Rules change, so check ldi.la.gov/fortifyhomes.If your roof is old, the Louisiana Department of Insurance runs the Fortify Homes Program. It offers grants up to $10,000 to eligible homeowners to upgrade roofs to the FORTIFIED standard, and Lafayette Parish is on its list. Rules change, so check ldi.la.gov/fortifyhomes. We also cover storm prep in our hurricane season roof guide.

Habits That Cut Algae on Any Roof

ARMA lists steps that discourage growth no matter what shingles you have.

1. Trim branches so more sun reaches the roof and fewer leaves land on it.
2. Clear debris with a leaf blower or another non abrasive method. Blow down the slope so debris does not get pushed under shingle edges.
3. Keep gutters clean. Do not let an upper roof drain straight onto a lower roof. Extend the downspout into the lower gutter.
4. Soft wash when streaks first show. ARMA describes a diluted bleach solution left on for 15 to 20 minutes, then a gentle rinse.
5. Never pressure wash shingles. ARMA warns it strips granules and very likely causes early failure.

Questions to Ask Before You Reroof

• Which shingle line and warranty tier are you quoting?
• Does the algae warranty need matching hip and ridge shingles?
• Who files the claim if streaks appear, you or the manufacturer?
• Will copper runoff touch my aluminum gutters?
• Is this installation wind rated for hurricane season?

Frequently Asked Questions

Next Steps for Your Roof

If your roof is streaked today, start with a gentle roof cleaning. We serve Lafayette, Youngsville, Broussard, and Carencro, along with the rest of our service areas. We will tell you honestly whether you have algae, moss, or damage that needs a roofer.

Planning a new roof? Use the questions above, and send us a photo if you want a second opinion on what is growing. Get a free estimate, or read more on our blog and about us pages.