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Community and Q&A

Snap-on metal roofing vs. traditional folded on site

Larry Burks | Posted in General Questions on

Anyone experienced with the differences between a traditionally installed metal roof (metal formed and folded on site) versus some of the new snap-on type metal roofing systems? I like the look of a traditional metal roof, but some of the quotes Im getting are well above my estimates (it’s a very simple roof!). The snap-on system I’m considering is the same type steel and gage. I’ll also be installing solar PV on the south-facing side at a later date. Will a snap-on actually be cheaper? Will it last as long? Will it work well with PVs installed on it? What are the drawbacks? House is in upstate New York region. Thanks for your thoughts.

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Larry,
    I'm unfamiliar with the term "snap-on," but a Google search seems to reveal that the "snap-on" systems are what I call standing-seam metal roofs. These roof panels are usually formed and cut on site.

    Here in Vermont, the less expensive alternative to a standing-seam metal roof is a traditional through-fastened metal roof. Twenty years ago, we all ordered metal roofing panels (30" or 36" wide) in 8 ft., 10. ft., or 12 ft lengths; now any lumber yard will deliver panels to your exact measurement, down to the quarter inch. You can order panels 17' 3 3/4" long if you want, in a wide variety of colors. They are usually 36" wide.

    If your roof configuration is simple, without a lot of valleys, hips, dormers, and penetrations, such roofs go up fast.

  2. Larry Burks | | #2

    Thanks Martin,

    Sorry, I should have included an example. Here's one of the companies that we've been looking at.

    http://www.aspincorp.com/pages/1/Product%20--slash--%20Specifications/Product%20--slash--%20Specifications/

    I threw out the notion of a through-fastened metal roof early in the process because I read that there were problems with the expansion and contraction of the metal rubbing against the screws. And I assumed the fewer the penetrations in the metal the better. But maybe I should reconsider.

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Larry,
    The link you provided is a type of standing-seam roof. If that's what you want, go for it. It's an excellent roofing, but it will cost more than through-fastened steel roofing.

  4. TJ Elder | | #4

    Your best bet for durability is a roof with concealed fasteners, like most of the standing seam systems. They use a cleat that folds into the seams and is fastened under the roof surface. Exposed fasteners typically have rubber gaskets that have a limited lifespan, and when they wear out (become crumbly after years of UV exposure) the penetrations can leak.

  5. Riversong | | #5

    Larry,

    The snap-on metal roofs cost somewhere between a screw-down and a hand-crimped true standing seam roof. Some types are, in fact, a compromise between the two, requiring exposed screws at the top and bottom of each pan with the rest secured with hidden clips or build-in nailing flanges.

    Some systems have pans that simply snap onto each other, while others use separate "battens" that snap over the joint between pans.

    Because the snap-on systems rely on standardized factory-made edge and end trim that don't require forming on site, they are faster to install and can save on labor costs but might be problematic on complex roofs with lots of penetrations, such as skylights, dormers and chimneys.

    The quality and longevity of these roofs will depend on both the quality and gauge of the metal and its finish as well as the skill of the installer. I've seen beautiful screw-down and clip-on roofs and awful standing seam jobs.

    As for PV installation, the standing seam clamps that make PV panels a "snap" to install cleanly and securely won't likely work on most snap-on roofs, since the seams are not flat and tight and the "battens" will compress and distort.

    Before choosing a roofing system, I would suggest conferring with your PV installer on the relative benefits and compatibility issues with each system. True standing seam is certainly the "cadillac" of metal roofing systems - IF it's done well.

  6. Riversong | | #6

    Martin,

    The snap-on metal roofing systems are not true standing seam roofs, since they typically require no on-site forming, no hand forming or hand crimping. They use factory-made trim stock and various proprietary methods for interlocking the panels. Some are more sophisticated than others, but they are all compromises between true standing seam and screw-down preformed panels.

  7. Riversong | | #7

    Larry,

    There are also thin film PV systems designed for standing seam roofs that attach directly to the metal pans or preformed combination metal/PV roofs that may be worth considering.

    I know people here in Vermont who were waiting in line for availability of the thin film PV, since it's so much less obtrusive than crystalline panels.

  8. David Meiland | | #8

    We regularly install what we call "snap lock" metal roofing. All of the panel fasteners are concealed, but the trim is attached with washer screws that need periodic replacement. The better products are 24-gauge with a Kynar paint finish and will look good for way longer than any asphalt roof. A metal roof makes it much harder to get on top to clean the chimney or do other maintenance, but I'd still rather have metal, assuming the building style is appropriate. My favorite brand is Nu-Ray Metals but for the most part you use what is produced regionally.

    One thing I like about snap-lock is that I can unsnap it and break into the middle of a roof if I need to. Start at the bottom, unzip one of the overlaps, and you're in.

    I've seen a couple of real standing-seam roofs go on. They were heavy copper and consisted of 10-foot pans made by the installer in his shop. No exposed fasteners. Should last 100 years and of course the cost is commensurate. A very good coppersmith I'm familiar with from another forum is at http://www.grantlogancopper.com

  9. Riversong | | #9

    Besides it being so difficult to get up on a metal roof for chimney cleaning, repairs or renovations, the other reason I steer away from metal is to avoid avalanches. Metal roofs commonly shear off plumbing vents and gutters, require that shrubs be protected by wooden A-frames in winter and make shoveling off the entry walk or garage apron an exercise in futility since the falling snow packs like concrete.

    But, for those who can afford the luxury of copper and slate roofs, I know of no better craftsman than Liam Tower of A Slate Affair Inc. Check out his portfolio at http://slateaffair.com/portfolio.asp.

    I recently took a course with him and learning to understand and work slate was one of the more satisfying things I've had the pleasure of doing.

  10. David Meiland | | #10

    I'm jealous. I would love to get some training in that.

    We get enough snow once every five years or so to cause minor problems, mainly small cornices forming on the gutters. Then it warms up and they disappear.

  11. Nathan Spriegel | | #11

    I thought "avalanches" were taken care of by snow guards/stoppers? I am considering using a metal roof on future home. One of the things I have seen listed in some manufacturers installation manuals was the placement rules for snow guards (X" from bottom, every X' vertically, etc.).

  12. Larry Burks | | #12

    And do snow guards really stop avalanches on a 12/12 pitch metal roof?

  13. Nathan Spriegel | | #13

    Not required. Again, per the manufacturers instructions I have reviewed, a high-slope roof will shed the snow as it falls. Therefore you will not build up a lot of snow to be an issue. And on a very low-slope roof the snow will just sit there until it melts.

  14. User avatar GBA Editor
    Martin Holladay | | #14

    Nathan,
    I have a steel roof with a 12:12 pitch. The snow definitely does not "shed the snow as it falls." The snow stays on my roof from mid-November to some time in April.

  15. Nathan Spriegel | | #15

    Hm, thanks for the real world observation. I will rethink some things then. I was going off of manufacturer recommendations.

    Fabral for instance, states in their tech bulletin 722 "The steeper the pitch, the more snow will tend to slide off a metal roof. On very steep pitches, such as 12:12 pitches, snow will tend to slide off immediately and not build up to the point where it will create a problem. As a result, snow guards may not be required on very steep pitches. On shallow pitches, below 2:12, the snow will not tend to slide off the roof; it will melt in place and run off as water. Again, snow guards will not do much good and may not be necessary. Pitches between 2:12 and 12:12 are where snow guards should be considered for use where sliding snow will cause damage to property or people below."

    That is the difference between theory and reality. Things don't always behave as expected. As I will be using a slightly less that 2/12 slope I will go ahead and include snow guards "just in case". Last thing anyone needs is a few hundred cubic feet of snow landing on their head!

  16. David Meiland | | #16

    What type of metal installation are you putting on a <2:12 pitch?

  17. Interested Onlooker | | #17

    Martin,
    With a steep metal roof, what is your experience of the sort of damage to gutters, vent pipes and shrubs that Robert warns of?

  18. User avatar GBA Editor
    Martin Holladay | | #18

    Interested,
    1. I don't have roof gutters.

    2. I don't have shrubs under the drip line. But really, there shouldn't be any reason to plant shrubs near a foundation anyway -- they just grow too tall and keep the bottom row of siding damp.

    3. Vent pipes should always be redirected towards the ridge, where the weight of the sliding snow is less. My vent pipes are fine, but a neighbor had vent pipe problems because the plumber didn't realize that the pipe should exit near the ridge.

  19. Nathan Spriegel | | #19

    David:
    This will be a shed-style roof over a very small house, 450-500 square feet for the main floor plus a basement. If you look up Tumbleweed Tiny House Co. "Z-glass" house it looks very similar to that.

    Usually manufacturers do not recommend using a standing-seam at such a low angle. However some snap-lock panels have tall seams which allows for a low-slope installation. For instance, Fabral's 1-1/2" seam SSR panel is listed for 1/12 slope.

  20. Accordian | | #20

    Upstate New York here with a 12/12 standing seam copper roof (fabricated on site). It is a beautiful roof but has no snow guards - I can tell you the snow comes off the roof in a great clump when it reaches critical mass - definitely compacts to ice which is impossible to shovel - the year before last the snow coming down couldn't go anywhere due to the volume of compacted snow below and formed a wall of snow from mid-roof all the way to the ground. Couldn't see out the windows at all. Another year, the snow load coming down all in a clump tore the heavy wooden top (3"thick mahogany, 5' diameter) right off a build-in outdoor table (steel frame anchored under flagstone of terrace) and crushed it to splinters. You definitely don't want to be standing under the eaves of a 12/12 standing seam roof if there is any possibility of heavy snow! Someone just told me about snow guards and I'm trying to find any company who will install them without soldering to the panels - so if you are thinking of a standing seam roof and live in an area that gets a lot of snow definitely have the original roofer put those on.

  21. Aj Builder, Upstate NY Zone 6a | | #21

    I grew up in a home that had the back roof converted to metal. The roofer said it would help with ice dams. It did, it just transferred the water disaster to our cellar. Snow came off the roof and made a huge ice bank in the back yard which was only not an issue because it was in the back. Then spring arrives and spring rain and... two inches or water in a carpeted cellar game room. Sweet. Loved mopping that up annually; big bonding session with an irate pop and siblings...

    Metal roofs in snow country... plan for how you deal with the unintended consequences.

  22. Riversong | | #22

    Accordion,

    Contact Liam Tower at http://slateaffair.com/. He's one of the most skilled slate and copper roofers in the northeast.

  23. Jack Woolfe | | #23

    Fabral for instance, states in their tech bulletin 722 "The steeper the pitch, the more snow will tend to slide off a metal roof. On very steep pitches, such as 12:12 pitches, snow will tend to slide off immediately and not build up to the point where it will create a problem. As a result, snow guards may not be required on very steep pitches. On shallow pitches, below 2:12, the snow will not tend to slide off the roof; it will melt in place and run off as water. Again, snow guards will not do much good and may not be necessary. Pitches between 2:12 and 12:12 are where snow guards should be considered for use where sliding snow will cause damage to property or people below."

    I'm late to the party, but FWIW... I have a through-fastened 3/12 pitch metal roof. After a heavy snowfall, and especially when the day is sunny and warm, the snow s-l-o-w-l-y slides off. It can form a cornice or curl of snow about 2' in diameter under the eave -- until it breaks off. Usually the whole cornice goes at once. The roof "snaps" slightly upon being relieved of the weight, and you can feel the thump in the house when the snow lands 12' below. It's rather entertaining to watch, but it would be scary if I had small children about.

  24. Kade Smith | | #24

    I'm late to the party was well Jack, but I saw a video of one of those cornaces fall off on a car and totally smash in the front end of it. I think I saw it on the blog of http://www.roofthings.com, but I don't remember for sure. Anyway you look at it, those things have a lot of power.

    As far as using snow stoppers on a 12/12 pitched roof, yeah they'd work, but you'd have to put them all the way up the roof I would think.

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