Metal Roofs

April 26, 2008 5:55 PM

I am thinking of installing a metal roof. I am in central New England. My present shingled roof has a 3½" to 12 pitch and is rated for up to 30 pounds per square foot. This winter The roof had to be shoveled on a regular basis. I am both worried that with heavy repeated snows my home is at risk for structural damage and I suspect that this 30 PSF rating is not a real world figure. I also have a problem with heavy snow blocking the combustion air for my furnace which is built into the furnace stack. Would a dark colored metal roof with such a shallow pitch be self clearing under heavy snow?
posted by Raybun to home & garden (5 comments total)

I have a dark-colored steel roof with a MUCH steeper pitch than yours (mine is 12 over 12 and 18 over 12). I also have some porch roofs which are about 6 over 12, so still steeper than yours. Here's the skinny on how they shed snow:

18 over 12 -- no problem. Snow slides straight off.

12 over 12 -- some wet snow sticks. When the sun comes out and warms the roof, there are mini avalanches to the porch roofs below.

6 over 12 -- snow accumulates.

Bottom line, it won't clear. The only solutions I can think of are a roof shovel (I have one of these) or a heating loop.
posted by unSane at 6:59 PM on April 26

Sorry, meant to say, I am in the snow belt of Ontario, so we get a LOT of snow.
posted by unSane at 7:00 PM on April 26

The problem with snow in Massachusetts is that a lot of the time when it comes down, it comes down really hard and accumulates rapidly. Temperature is low, cloud cover is heavy -- and that means no solar heat to warm up a dark roof.

By the time the sun does come out, after the storm, enough snow will have accumulated so that the albedo is white, not dark. The only time the dark color will become a factor is after most of the snow has melted off anyway, due to ambient temperature being above freezing.

As unSane says, in the end there's no substitute for a steep pitch.
posted by Class Goat at 7:58 PM on April 26

My wife and I live in central Vermont and are building a new building this summer. Since our asphalt shingle roof is near the end of its lifespan we decided to replace it while the roofer is here to do the other building. We are switching to standing steel because it last much longer, but our contractor said the color of the standing steel roof really does nothing to change the snow melt. Our architect concurred.

So as Class Goat and unSane have said, it will be the pitch and a good roof shovel that will be the biggest difference.

Also, this past winter Vermont had record snow falls and my very old shingle roof held up fine. I had asked my contractor (who is a friend and neighbor) if I should be concerned enough to be climbing out of the dormers to clear the snow and he told me that my newer house (1992) should hold up fine. I still bought a roof rake/shovel and cleared what I could, but only from ground level.

You didn't mention if your home is newer or older.

YMMV
posted by terrapin at 4:01 AM on April 27

The benefit of a metal roof is not just that it will shed snow, given a sufficient pitch, but also that there will not be any backup of ice under shingles as the thaw-refreeze starts. (In my mind, this would make heating loops unnecessary.) You will still need to shovel a low-pitch roof but the shoveling will be a lot easier.
posted by megatherium at 4:04 AM on April 27