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TOPIC: Exposed Fasteners

At what pitch does snow slide off?

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I am building a new home, for myself for a change, and I think I will use an exposed fastener metal roof. I was planning on a 4/12 pitch. At what pitch does snow slide off?
Guest User

8/4/2010
This has more to do with weather conditions than pitch. Snow can certainly slide off of a 4:12 roof. However, the larger factor is that when the sun comes out, radiant heat passes through the snow, is reflected outward, melts the snow from underneath and causes it to slide.
Todd Miller
Isaiah Industries, Inc.

8/5/2010
My concern is piles of snow next to building and gutters being damaged. But I don't want to see snow holds. Any recommendations? I love your forum, the Insulation Concrete Form Association (ICFA) should have one like it.
Guest User

8/5/2010
Snow will slide off at just about any pitch. Ice damns and fast melts are more a result of air and heat leaving the structure as opposed to exterior melting. Your best bet is to hold the snow load and let it melt slowly. If you put extra spikes or hangers in the gutters and a gutter cover, that will help allow the snow to slide off.
Eric Novotny
An informed customer is the Best Customer!

8/6/2010
I will have a super insulated attic. I was also thinking of a darker color. How will that affect performance. Does dark colors last as long as light colors? Does plain galvanized last as long as painted?
Guest User

8/7/2010
Super insulated is definitely a plus. Make sure the air loss/exfiltration is addressed as well and you should avoid a lot of unnecessary melting. The new darker colors are quite good. Empirically, one would theorize that the panel that remains cooler and reflects less of the sun energy will live a happier life. Most panels are galvanized and then painted, not one or the other.
Eric Novotny
An informed customer is the Best Customer!

8/7/2010
I plan on using lots of ridge vent (and soffit), any suggestions on types of ridge vent? I know the painted metal is galvanized first, so I would think painted would last longer.
Guest User

8/7/2010
I don't think you got what I meant by exfiltration from the living space. See the picture below. What is the roof construction (truss, sip, etc)? Depending on the construction, the necessity of ventilation may be nil. For example, if you are running a SIPs roof, you are better served to turn that attic space into conditioned space (seal it up from any ventilation and place some HVAC supply and return lines in it). What is going in the attic?
Eric Novotny
An informed customer is the Best Customer!

8/8/2010
I want to build a metal roof attached to my barn over my wood pile. Since this is not a heated space, what kind of inexpensive metal roofing would allow snow to slide off most easily and at what minimum pitch. We sometimes get 12-24" snowfalls here in Western Massachusetts.
Guest User

8/11/2010
It will be about 7,500sf on wood trusses with a vented attic. I will have about 2500 sf of metal roofing that will be over living space with 2" spray foam to seal and insulate, then lots of blown-in on on the ceiling. The other 5,000sf will be non-climate controlled, insulated, nor will it have a ceiling until I can afford it.
Guest User

8/26/2010
Sounds like you have got it down to a science. If the sprayfoam is costly, there is no need to spray foam and seal the entire attic floor, just the penetrations, top plates, and any other envelope breaches. Cellulose (use a borate only) is relatively cheap. I would put in R-50 as a minimum but you can put in more. It doesn't hurt.
Eric Novotny
An informed customer is the Best Customer!

8/27/2010