galvanized metal roofing, durability?

[Ccat]

In the Puna rainforest, how long do galvanized metal (corrugated) roofing panels last?

[terracore]

I don't think there is a single answer to this. If they are regularly cleaned and repainted when necessary I've heard of them lasting up to 70 years, a theoretical figure considering they are guestimating on newer products that haven't been around that long. On the other hand, there were people complaining that the acid rain and fumes from the Leilani eruption were causing a chemical reaction with the galvanizing.

And then you have to consider that 10 or 20 years from now somebody may come out with a new product that adds even more life to them.

I saw an older, neglected, galvanized steel roof in Volcano where much of the paint was gone and the metal was rusting. The owner paid somebody who cleaned, treated, and repainted it and it looked like new. I can't remember how much they told me it cost but I do remember being very surprised at how affordable it was. I saw the same roof about 9 months later, still looked brand new, but whether the miracle coating will really last, I don't know.

We're in the process of getting someone to clean and inspect our roof (15 years old so overdue) now.

[Rob Tucker]

Your best bet is a product called Galvalume. Better than simple galvanized.

[BlackAkita]

Your best bet is a product called Galvalume.  Better than simple galvanized.

The manufacturer claims that Galvalume (the budget line) costs about the same as normal galvanized roofing. I should know in a few months or years (lol) whether this is true or not, because I will ask for it in the As-Built plan I will file. Do birds peck at a roof?

[Durian Fiend]

I've never heard birds pecking on my metal roof, and it has no roof deck. Sometimes they will walk on it for a few seconds.

[BlackAkita]

My reading of how Aluminum and zinc protects the steel or iron base of the roof tells me if the top layer wears away or is scratched off, then galvanic corrosion can occur. The other two substances it needs are an electrolyte (ionized water) and an unfriendly metallic element.
https://www.atas.com/wp-content/uploads/...FINAL2.pdf
Everything wears away eventually, including acrylic coatings. I hope the birds will not poop on the roof, or claw away at it.

[Chas]

My roof is aluminum.

[HiloJulie]

“I hope the birds won’t poop on the roof”

Unfortunately, that’s like hoping that it won’t rain here in Hilo!

At any event, regular cleaning of your roof panels regardless of composition as well as gutters will ensure a very long lasting life span. 

One of the best ways to keep your roof in tip top shape is cover it with solar panels!

Good luck in your future endeavors!

[Durian Fiend]

...Everything wears away eventually, including acrylic coatings. I hope the birds will not poop on the roof, or claw away at it.

They might occasionally poop on it. Same with rats, although I've never noticed any type of poop on my roof when inspecting it.  Of course it would usually be washed away in short order with the abundant Puna rainfall. 

There's no reason for any critter to scratch/claw at it. 

The most common spot for metal roofing pieces to rust is at the drip edge. A new metal roof could very well last your lifetime, unless perhaps you're mid 30's or younger.

[kalakoa]

The most common spot for metal roofing pieces to rust is at the drip edge.

HPM sells a brush-on coating for this. I don't know how well it works because I sold the house.