What are your thoughts on a metal roof?

[Sam Zawatsky]

I am needing to get a new roof on one of my Tallahassee properties in the next couple of months. What are your thoughts on metal roofs? How does it affect value and rentability, compared to standard architectural shingle roofs?

[Jesse L. Weaver]

Quote from @JD Martin:

Quote from @Jonathan R McLaughlin:

@JD Martin what is the expected lifespan on these anyway? I just looked at a few places with what looked like really cheap metal roofs and find it hard to believe they would hold up. Assume the premium stuff is better. Any issues with screw holes leaking etc?

They use screws with rubber washers on the roof ribs, which is the high point and where water runs away anyway so the risk of leaking is already severely minimized. And if you have a decent asphalt roof already on there, one that's old but not destroyed, and not multiple layers, they go right over it which gives you a waterproof underlayment (and a sound dampener, metal roofs can be loud). The leak risk areas are at the flashing points and at the valleys. The roofing material itself is fairly thin - even the really old stuff - but if it's galvanized and painted besides (most of the new stuff is powder coated) you are talking decades before you even think about rust.

If I had to think of any risk of metal roof it would be peeling off in high wind/hurricane areas, because it comes in long sheets. So if the installer didn't use the proper number of screws, didn't get into solid roof sheathing, etc, then that could be an issue, but that would also be an insurance claim issue anyway. Other place I wouldn't use it is if you have a lot of trees that drop heavy items on the house. I didn't put it on my house because I have several hickory trees nearby that drop huge nuts that dent the hell out of metal roofing but don't bother the asphalt at all.

Our local metal roofing manufacturer in Lancaster, PA offers a 40 year warranty on their finish. They also sell a screw that improves on the standard rubber washer- it has a metal dome coming down from the screw head that covers the rubber washer. Most fastener failures I've seen have been the result of over tightening screws and sun eventually breaking down that rubber washer. Another failure point is when the screw cuts through the metal when it's being driven it can create a metal burr that sticks through the washer. This eventually rusts and allows water in. A self drilling screw point solves this issue.

I prefer screws going into the flat portion of the metal panel and not into the rib. There's more flexibility at the rib vs. a flat spot fastening tight to the wood underneath. Which results in less screws backing out/becoming loose. A screw that loosens on the high part (rib) will allow a lot more water in than a screw that stays tight- even if it is on the flat spot that sees a little more water. Or spend the extra money and go with a standing seam metal roof- no exposed fasteners! Like you mentioned, I would check local codes and look into required fastener patterns because high winds can definitely be an issue and are something we don't have to worry about as much in PA compared to FL.

Metal roof flashing is an art and I've seen many more flashings installed incorrectly and rely on caulk than I've seen installed correctly. By far the number 1 place for problems to occur. Make sure you are working with an expert and specifically ask about their flashing processes on roofs that would be similar to yours.