We recently got a fantastic question in the comments section of our post, "A Rustic, Natural Metal Roof - Made to Order." Here was the original comment and question:
"Love the rust patina! However, how does this affect the lifespan of the roof? I know with older cars rust is quite an issue and their metal is far thicker than these tiles. How long would an unfinished vs a finished steel roof last?"
We responded directly to this visitor, but it's such a great question, we thought we'd share it here for anyone else who's ever wondered the same thing. Of course, the rusting of metal compromises its lifespan and this observation of the rusty cars makes nothing but sense. The big variable with bare steel and its lifespan as a roof is location. Just like steel car bodies lasting much longer in Arizona than Florida, steel doesn't rust nearly as quickly in dry climates when compared to humid. Other variables, which are nearly as significant, include specifics of the application: overhanging trees, pitch of the roof, configuration of the roof (does it hold debris and moisture?), alloy of steel, thickness of steel, pattern and underlayment. All of these factors contribute to either allowing the roof to dry out (extending its lifespan), or continually stay wet (compromising its lifespan).
There are design considerations that address all of these issues and with the exception of a few very humid and warm (since salt water exposure, moisture and heat are the biggest contributors to steel corrosion) locales, bare steel roofing with its classic, rusty patina can offer a useful (30+ years) lifespan in most US states.
If you have a particular project in mind, we offer a free design consultation and will gladly offer an expert opinion on the most suitable choices for your job.