Reuben's Home Inspection Blog

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A semi-long term experiment: zinc strips on a moss covered roof

While black stains on roofs are a cosmetic issue, moss growth is more than just cosmetic.  Not only does moss look terrible on roofs, it will also shorten the life of the roof covering and possibly lead to roof leaks.  Whether you have wood or asphalt shingles, moss can grow on the roof if it doesn't dry properly.

As with black algae stains, the most common place for moss to grow is on the north side of the roof, but if there are enough overhanging trees or other forms of shade, moss can really grow anywhere.  If you want to kill the moss, follow the link above that explains how to remove black roof stains; the process is the same for killing moss.  The results certainly won't be as immediate, but it's effective.  Today, the focus is on what you can do to prevent moss growth on your roof.

Have you ever noticed that moss and black stains don't appear on roofs underneath the areas with galvanized metal?

Zinc washing off roof vents

The roof stays minty fresh zincy fresh below the vents because every time it rains, a small bit of zinc gets washed off the metal, which runs down the roof and kills whatever is growing on the shingles - whether it's moss, algae, lichens... whatever.  If this is so effective, doesn't it stand to reason that you could install strips of zinc along the top of the roof, and have them protect everything?  Of course.  You can actually buy rolls of zinc made just for this purpose.  The 50' roll of zinc pictured below was about $25 at Home Depot.

Zinc Roll

The zinc is supposed to be installed at the ridges of the roof, or along the hips as needed to make sure that the rainwater washes zinc down the roof.

Zinc Strips Installed

Zinc Strips Installed

I've heard many roofers say that these zinc strips are worthless and ineffective, so I decided to conduct my own semi-long term test.  For my experiment, I installed a zinc strip along the ridge of a moss-covered garage roof approximately sixteen months ago.  I didn't do anything else to this roof - no scrubbing, no chemicals, no nothing.  The before and after photos are shown below, and I think the results are pretty conclusive - zinc strips are effective at killing moss.

Before

Mossy roof before

After

Mossy roof after

That's a pretty dramatic difference, isn't it?  I cleaned up the roof a bit before taking the second photo by using a leaf blower, but that was all.  Remember, I applied that zinc strip to a roof covered in moss just to see what would happen; zinc strips aren't supposed to be used as a moss remover, they're supposed to be used as a moss preventer.  If you're not in any hurry, they'll apparently remove moss too though.

As they say, individual results may vary.  Zinc strips might not work for every application, but they're not terribly expensive, and they're not difficult for a roofer to install.  If you have an existing roof with a moss problem, try zinc strips.  Copper strips are supposed to work the same way.

Zinc strips are also supposed to be effective at preventing black stains from showing up on the roof.  I'm starting a long-term experiment on my own house; I'll report back with the results in a couple years.

Stay tuned  ;-)

 

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 64 commentsReuben Saltzman • November 08 2011 06:04AM

Comments

Hey Rueben-I think I am going to get into the zinc business now! That is amazing. I had seriously wondered why the roof stayed clean under a galvanized vent and now I know-thanks!

Posted by Marco Giancola, Realtor (305)608-1922, Miami Beach Florida (Beachfront Realty) over 6 years ago

Amazing. This looks like a great idea. I will have to suggest this to those with a moss problem and those that are reroofing or building new. Cheap and easy way to keep you roof nice and clean. Thank you!

Posted by Diane Grady (Endless Summer Realty) over 6 years ago

Reuben: Every picture tells a story. I've had moss delay the sale of a house for almost a year - until the owner had it cleaned by a professional. This looks like a great solution.

Posted by Anne M. Costello (Weidel Realtors) over 6 years ago

My roofer told me they work, but only for about 5 or 6'.  He also said they run out of zinc.  I'm not sure that is possible, but it might be that the quality of the zinc diminishes with time.

Don't know!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 6 years ago

Marc - the funny thing is, these zinc strips are nothing new.  I really can't understand why I don't see more of them.

Diane - thanks.  When it comes time to install new shingles, you can actually buy shingles that are moss and algae resistance; they're coated with zinc or copper to help inhibit growth.

While black stains on roofs are a cosmetic issue, moss growth is more than just cosmetic.  Not only does moss look terrible on roofs, it will also shorten the life of the roof covering and possibly lead to roof leaks.

Anne - and I bet having the roof professionally cleaned only cost a few hundred dollars, right?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Jay - I've heard the same thing repeated many times before.  That's why I decided to try this test on my own.  If the zinc strip is ninety-nine-point-something percent zinc, how does it diminish?  

I don't know either.  Maybe I'll have some bad news in ten years ;-)

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Reuben, that is absolutely amazing. And considering that a lot of HOAs send out notices to clean your roof (when it gets stained black), this is a fabulous long term solution to a recurring problem. Any idea as to the per foot cost of a retrofit on existing asphalt shingle roofs?

Posted by Beverly Jo Cole (Southern Cross Real Estate, Inc.) over 6 years ago

Wow, Reuben, what an amazing product! Who knew? OK, I am sure some of you knew, but I sure didn't. If it prolongs the life of a roof, especially one that would be prone to growth on the roof, it is a must do for a new roof for sure.

Posted by Andrea Swiedler, Realtor, Southern Litchfield County CT (Berkshire Hathaway HomeServices New England Properties) over 6 years ago

Beverly - the zinc strip I used was about fifty cents per foot, and the installation was pretty quick and easy.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Reuben,

That's pretty conclusive proof!  I'd never heard of this until reading your post.

Mike in Tucson

Posted by Mike Jones, Mike Jones NMLS 223495 (SUNSTREET MORTGAGE, LLC (BK-0907366, NMLS 145171) ) over 6 years ago

I have a roof covered with moss on the north side. Great idea!

Posted by Mark Robinson, Honesty, Integrity, Service (Geneva Financial, LLC) over 6 years ago

Rueben...

Pretty interesting .... but what about the discharge through the gutter system. I wonder if it's harmful?

Posted by Richard Weisser, Richard Weisser Retired Real Estate Professional (Richard Weisser Realty) over 6 years ago

Funny I've heard the same slams against zinc strips. If it was true how come roofs with copper or zinc coated metals are clean all the way down to the soffit? More industry myths? 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 6 years ago

Rueben

Great experiment.  Of course the roofer is going to say they wont work. Then people wont change roofs because they are ugly.  A friend of mine started a roof cleaning business and he is doing pretty well with it.  Who would have thought.

Lee

Posted by Lee Floyd (Race City Inspections Inc) over 6 years ago

Hi Rueben.   Nice info for us especially with the photos from your experiment.   Thanks.

Posted by Carol-Ann Palmieri, "Cal" the Real Estate Gal (RE/MAX Executive Realty, Al and Cal Realty Group) over 6 years ago

Mike - thanks for reading.

Mark - you'll have to take before and after pictures.  Stop by in a couple of years and post your results :)

Richard - no harm to the gutters.  The zinc is perfectly safe.

James - Yes, I think this is an industry myth that the zinc strips don't work.

Lee - it's funny, I've never run across anyone in my area that advertises roof cleaning.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Carol Ann - thanks.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Reuben,

that is informative...thank you for the photos.  We'll mention it to our clients when that topic infrequently comes up, but indeed a visual education you've done.

Michael

Posted by Michael Hobbs, SRA, LEED GA, RAA (PahRoo Appraisal & Consultancy) over 6 years ago

Btw I'm going to try this myself. I have one section of mossy roof. Looks like I'll be going to HD.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 6 years ago

Good morning, Reuben....great post.....I have one side of a porch roof that beginning to look discolored....now I know the solution to this problem....thanks

Posted by Barbara Todaro, "Franklin MA Homes" (RE/MAX Executive Realty ) over 6 years ago

i love it when science meets real estate! great post.

Posted by Randy Harden, www.RERandy.com (Wieder Realty, Inc.) over 6 years ago

I don't know either.  Steve (my roofer friend, 20 years in the biz, and has seen it all) said that it loses potency over time, either from the sun or repeated washing with rains.

Other than that I have no proof of any sort.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 6 years ago

Reuben, $25.00 is a small investment and is worth giving it a try.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA over 6 years ago

Reuben, the zinc can develope an oxide covering (rust) that diminishes its effectiveness and Jay is right about the 6' thing I think.  Out here (moss country) roofers will put them at the ridge and the middle of the run of the roof and they are effective for quite some time---but I have also seen roofs with zinc strips that have plenty of moss---will see if I can find some pictures.  For some reason the vent caps seem to work better than the zinc strips at times :)  I also think there are different species of moss that respond better to zinc than others do.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 6 years ago

Great info Reuben.  Do you know if the strips would help with mold growth on cement tile roofs?

Posted by Gabe Sanders, Stuart Florida Real Estate (Real Estate of Florida specializing in Martin County Residential Homes, Condos and Land Sales) over 6 years ago

Reuben that is a fantastic report, i get the black stains on the north side that doesnt get any direct sunlight. i will certainly be giving it a try. Thanks for the tip

Posted by Scott Godzyk, One of Manchester NH's Leading Agents (Godzyk Real Estate Services) over 6 years ago

Thanks for the outstanding information. 

Posted by Kathy Seger & Ben Staten, Red Hot Atlanta Homes Group (RE/MAX Around Atlanta) over 6 years ago

This is great information.  It didn't sound like it cost much for the supplies and I'd assume not take the roofer too long to install if they are already doing the roof work already.

Posted by Morgan Evans, LICENSED REAL ESTATE SALESPERSON (Douglas Elliman Real Estate) over 6 years ago

This man has the makings of a professional or expert witness...He makes a compelling point for the layman to appreciate and investigate...good educational post...thank you Reuben

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) over 6 years ago

Reuben,

We have so much moss around here. I think the strips are effective but the problem is, like with gutter guards, the people decide that they have permanently solved the problem. So they ignore the roof or the gutters and we inspectors go up on the roof and find the wind has torn the zinc loose and moss is, once again, in control because nobody has done anything in years. I would say that the zinc strips help slow moss growth, but you still need to maintain a roof and many people who put the strips on forget that or do not know that.

Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) over 6 years ago

I love your experiments!  I remember one with icicles or what is that horrible winter condition... ice dams?  Or ice damns?  Damn I am not looking forward to winter this year.  They say it is going to be a bad one in our area... not sure who they are but I read it is going to be a rough winter. 

This is great.  I don't believe we have as big a problem with moss on roofs here as some parts of the country (PNW comes to mind) we get a lot of rain but are a lot warmer in the summer than WI, MN, MI.   We do have ugly algae stains on roofs in this area and I just noticed how they were NOT below the metal vent caps at some house I was sitting in front of the other day so your first photo grabbed me. 

Posted by Maureen McCabe, Columbus Ohio Real Estate (HER Realtors) over 6 years ago

I just learned something new today.

As always, your posts are terrific and very informative.

Thanks for sharing it.

Posted by Anthony Daniels, SF Bay Area REO Specialist (Coldwell Banker) over 6 years ago

Hi Reuben - Again, great information. I have never heard of it but will definitely recommend it to clients who need to know.

Posted by Peggy Chirico, REALTOR® 860-748-8900, Hartford & Tolland County Real Estate (Prudential CT Realty) over 6 years ago

Reuben, great tip. I never would have known. Thank you for sharing with the rest of us on Active Rain

Posted by Donald Reich (Prudential Centennial) over 6 years ago

I LOVE it when people test things out themselves instead of just going with 'common knowledge'. Most people just keep repeating whatever they hear, without ever being sure of what they're saying.

Posted by Joetta Fort, Independent Broker, Homes Denver to Boulder (The DiGiorgio Group) over 6 years ago

Thanks for info on zinc strips for keeping shingles clean, Rueben.  We will definitely use your blog and advice to keep our clients informed.

Posted by Bonnie & Terry Westbrook, Grand Rapids MI Real Estate (Westbrook Realty) over 6 years ago

Reuben -- I may have to get some of these strips for my mother-in-law's house, as well as my own.  The moss seems to like to grow on everything around here (even have it on some concrete stepping blocks.)

Posted by Steven Cook (No Longer Processing Mortgages.) over 6 years ago

This is an interesting post. I have never heard of the zinc use for algae. Amazing what you learn on AR!

Posted by Gary L. Waters, Broker Owner, Waters Realty of Brevard, LLC, ... a small office, delivering big service! (Waters Realty of Brevard, LLC) over 6 years ago

Reuben, I have never heard of this before... but the evidence speaks for itself. I know a few people that would love this information, thanks for sharing it.. I will be waiting impatiently for your next post.

Posted by Chris Smith, South Simcoe, Caledon, King, Orangeville Real Esta (Re/Max Chay Realty Inc., Brokerage) over 6 years ago
Really interesting & good to know. Thanks for sharing!
Posted by Melissa Marro, Jacksonville Real Estate and Home Staging (Keller Williams First Coast Realty - The Marro Team) over 6 years ago

Interesting. I have a neighbor whose roof looks like that! Now i know why.

Posted by Erica Ramus, MRE, Schuylkill County PA Real Estate (Erica Ramus - Ramus Realty Group - Pottsville, PA ) over 6 years ago

This is great info!!!  This is very helpful info to the North Central Florida area roofs under oak & pine tree canopy.  

Posted by Christine Bohn, The Bohn Team, Gainesville FL (RE/MAX Professionals) over 6 years ago

Great post Reuben thanks for posting. My question is, can the zinc be applied after the roof was installed or exactly how did you put it on your roof?

Posted by Robert Amato (Bob Amato of Empire Home Mortgage Inc) over 6 years ago

Reuben,

 Love the experiment. Science and home inspection 101.

I think Charlie may have something there on the oxidation that may effect the effectiveness.

I look at it this way even if it work for a while it really is minor cost. You can afford to re-apply every so many years.

Now here is the next experiment. On one half of the combine Zinc strip with some powdered dishwasher detergent and see if the phosphates along with the zinc has a greater effect.

 

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 6 years ago

Reuben - this is very interesting to me personally. I have some moss starting to form on my roof right now. I am going to look into this. Thanks for this.

Posted by Robert and Lisa Hammerstein -201-315-8618, Bergen County NJ Real Estate (Keller Williams Valley Realty) over 6 years ago
Very interesting! I have not seen this problem here, but it is good to know. Thanks for sharing!!
Posted by Yvonne Burdette-Van Camp, "Home"work, I have the Answers! (To Buy and Sell Real Estate, see me at Southwest Missouri Realty) over 6 years ago

Good information, we have a lot of mold here in Georgia on the roofs.

Posted by Mary Macy, Top Agents Atlanta Metro (Top Agents Atlanta Metro) over 6 years ago

Great post and your photos really drive home the point. Thanks for posting.

Posted by George Bennett, Inactive Principal Broker, GRI (Inactive) over 6 years ago

Michael H - thanks.

James - don't forget to take before and after photos, and share them in a year or two.  I was pretty disappointed with my 'after' photos until I compared them to the 'before' photos.

Barbara - take photos :)

Randy - me too.

Jay - Charlie has his own theory on this.  I'm looking forward to seeing some photos from him showing rusted zinc strips.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Michael S - as long as you don't get hurt putting the zinc strips up, you don't have much to lose.

Charles - don't try to confuse me with the facts ;-).  

No, but seriously, that's interesting stuff.  I've seen very few zinc strips, ever, so I don't have much to go by.  They've been effective whenever I've seen them.  I'm looking forward to checking out whatever photos you have.

Gabe - I'm sure that zinc strips would have the same effect on cement tile roofs.

Scott - good luck.

Kathy & Ben - thanks for reading.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Morgan - yeah, this is a pretty inexpensive solution.  Maybe not permanent, but it's tough to say how long it will last.  If the shingles are being replaced, the best solution would be to install shingles that are algae resistant.

Richie - you're too kind :).  Thanks.

Steven - you're certainly right.  Maintenance is key.

Maureen - Thanks!  I just do these experiments because I want someone from Mythbusters to hire me.  Well, that, and I like to figure stuff out for myself.

Anthony - thank you.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Peggy - and you can tell 'em you've seen proof.

Donald - happy to.

Joetta - I hear you.  I feel the exact same way.  

Bonnie & Terry - thanks.

Steven - they're pretty simple to install.  Good luck.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Gary - I bet you'll start to notice those 'clean streaks' below roof vents now.

Chris - as always, thanks!  I don't have any experiments in the works at the moment though... 

Melissa - Happy to share.

Erica - I love understanding how this stuff works too.

Christine - thanks.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Bob - yes, these zinc strips can be installed at any time.  Click this link for a quick video - http://link.brightcove.com/services/player/bcpid77585800001?bckey=AQ~~,AAAAABmUTZc~,OoHKCvFbAEasQK7YTowGr-vje-3s9YWX&bclid=823382878&bctid=823321671

This video was shared on Andrea Swiedler's blog at http://newmilford-cthomes.com/roof-staining-moss-lichen-growth-prevention-in-new-milford-ct/

Donald - how would that work with the dishwasher soap?  Just pour the soap on?  How often?

Rober and Lisa - good luck.

Yvonne, Mary, George - thanks.


Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Reuben. I have never heard of this before but it makes sense, a very useful tip thanks.

Posted by David Popoff, Realtor®,SRS, Green ~ Fairfield County, Ct (DMK Real Estate ) over 6 years ago

Awesome results from a simple experiment. Some people will love this.

Posted by Brian Schulte, SFR, Sierra Vista, AZ (Allison James Estates & Homes) over 6 years ago

Reuben.  Your post reminded me of my brother.  He used to live in Bristish Columbia - lots or rain and then you get some more.  He decided to try to scrape off the moss on his roof, fell, was taken by ambulance to the hospital, stayed a day, got a blood clot in his broken leg and today (many many years later) he still has to wear tenser socks when flying.  We laughed but it isn't funny.  Don't do roofing work unless you are putting safetly first and that usually means a professional. 

Posted by Valerie Zinger, Home Organizer (House Proud Ottawa-Ontario-Canada) over 6 years ago

I have seen a product similar to this one used on a couple of homes before and I was skeptical.  After reading this post I'm just amazed.  I will have to check back with you and see how your next experiment turns out.  Great blog post!

Posted by Jim Hanson, CPI, Bettendorf, Iowa Home Inspector (Hanson Home Inspections LLC) over 6 years ago

Thanks for the link to the TOH video Reuben. Seems real easy. I will take before pictures and post them with pictures that I take in a year. Excellent post, thanks again.

Posted by Robert Amato (Bob Amato of Empire Home Mortgage Inc) over 6 years ago

David, Brian - thanks.

Valerie - I'm glad you could have a sense of humor about your brother's situation.  I think I would have had the same response, even though it certainly isn't funny.

Jim - I was always skeptical until trying this for myself as well.

Bob - I'm looking forward to those photos.  I hope your results are similar!

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Hi Reuben. This is an amazing tip for homeowners living in a moss-proned area. I'll be sharing this post for sure. Thanks!

Posted by E H (None) over 6 years ago

Nicely presented article Reuben. Your photos really tell the story.

But...............you could always just use black shingles:)

As for the service life of the zinc strips, at that cost, who cares! Just change it for a new strip if you start seeing moss or staining. It's a no-brainer.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) over 6 years ago

I've always noticed that light colored roofs under certain trees really turn quickly. I've had a couple of listings where buyers just freaked out because of this inspite of no leaks.  This is a really cool way to suggest an easy fix to a 'growing problem'.

I'm sure the copper strips would definately be more $$. Maybe the zinc oxidizes over time & doesn't become as effective as when it's new?

Posted by Lyn Sims, Schaumburg IL Area Real Estate (RE/MAX Suburban) over 6 years ago

Reuben-That's pretty amazing, and a great tip. You'll have to keep us informed with your little experiment, although the roof will probably need to be replaced before the zinc runs out.

Posted by Michael S. Bolton, MN Appraiser (Michael S. Bolton,Inc.) over 6 years ago

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