What types of metal roofs are worth it?

[woodswordsquire]

I've thought metal roofs were cool ever since the MMM article about them way back when. For the first time since the article came out, I actually need to put a new roof on something. It seems like they've come down in price, and there are more variations than there used to be.

How do I know if a metal roof rated for 50 years will actually last that long? Are some types better than others? The roofer I've talked to so far does "tuff rib", and also something they call pro appearance panel that's supposed to look like a standing seam roof without actually being standing seam.

I'm hiring roofers, because it needs to be done quickly and there are many, many other DIY projects I'll be busy with.

[uniwelder]

I've used the 'tuff rib' type metal roofing.  People just call it Ag(ricultural) Panels here.  It's 36" wide and you screw through it.  Lots of people will say it's garbage and leaks, but I haven't had a problem. 

The proper screw location is supposed to be through the flat span of the metal, but I've listened to the other half of installers that insist (logically to me) that it should go through the raised ribs.  The roof will never leak if the screws go through the ribs, but they might fatigue and could fail after some (10, 20, ??) years.  The easy solution is to just replace the screws if that happens.

I replaced my old metal roof with ag panels when we renovated 10 years ago.  The original was called '5V' style, in which lead capped nails were pounded through the raised V ribs.  The 65 year old roof didn't have any leaks, even though 10% of the nails were missing completely, and half had backed out significantly or lost their caps.  The 1x6 purlins underneath were in perfect shape.

I would not install a metal roof on top of existing shingles.  I have seen some houses done like that-- in particular, the one we live in now.  The previous owner had it installed just before putting on the market.  The contractor lays roofing paper on top of the shingles, and then fastens the metal roof directly to that.  Horrible idea, particularly if the screws go through the flat section of the panel.  The screws don't seat properly since the underlying surface is wavy and there are many screws with gaps from day one.  This is because if the screws are tightened completely, then the ripples of the shingles will show through, so instead, they just barely make contact.

[sonofsven]

Mine is a standing seam style; it's been up for 22 years. It needs a good washing on the north side. It's getting a little surface rust along the eave edge at the gutter. I've never had any problems. I cut in a woodstove double wall ss chimney and flashed it, which was a little tricky, but also has never leaked (knock on wood).
One of my roofers used to say a metal roof is only as good as the paint on it, which is true to a point.
I think simple roof structures are more amenable to metal roofing.  A busy roof in metal doesn't look as good to my eye, and the details are harder, hence, more expensive.
Comp roofing still makes the most sense economically, if you buy the thickest shingles you can easily get thirty years of use.
Metal roofs sound good in the rain, they also creak a bit from expansion and contraction.
Get a few quotes, ideally at least three. You'd be surprised how different they might be. Ask a supplier for contractor suggestions

[ChpBstrd]

Generally the screws will fail before the metal does. Specifically, the neoprene rubber washers will eventually crumble, and that will be your source of leaks. The cheapskate solution is to just replace all the screws in 20-30 years, one at a time. Basically a day project.

The preventative solution is to choose panels where the screws/nails are not exposed at all, like standing seam. However when I was replacing the roof on my barn, this style was special order and had some complexities around the edges, so I just went with the typical 5 rib design. I regret not spending a little more to get painted rather than galvanized, but my thinking at the time was to mop on a $50 5-gallon bucket of aluminum reinforced rubberized coating if it ever got rusty.