Help! I need to replace a thirty-three year old hot mop roof. The problem is, or one of the problems is, that the roof is a 2:12 pitch and is in Idaho where we receive lots of snow.
I really like the look and the durability of a steel roof and sliding snow is not a problem with the design; my questions are:
1) Will steel work with a 2:12 pitch?
2) Will the snow slide of such a low pitch?
3) Ice daming issues?
I should add that I also plan to remove & replace the plywood? and whatever insulation is with spray foam. I have also have been thinking of adding a cold roof with Boston ridges but that gets expensive and introduces engineering questions. The house has 3″ X 13″ gluelams 4′ on center which might not be beefy enough to handle the additional weight of a cold roof and the snow load requirements of 100lbs per S/F.
All feedback will be appreciated!
SunvalleyRay
Replies
Have you considered a rubber roof? Rubber is a good alternative on low-slope roofs, and ice-damming shouldn't be a problem since it is a continuous membrane.
Al Mollitor, Sharon MA
Yes, I have considered EPDM and also a TPO (thermoplastic polyofefin membrane) but am concerned that if I need to shovel the roof which happens here during big snow years that the material will not hold up.
"... if I need to shovel the roof which happens here during big snow years that the material will not hold up."Sweep it.Rich BeckmanAnother day, another tool.
2/12 is too low of a slope for metal roofs. Best bet would be the TPO or EPDM and be careful when you shovel. i.e. do not go all the way down to the membrane.
Why do you say a 2 X 12 pitch is to low for a metal roof?
Sunvalleyray
2/12 is too low of a slope for metal roofs.
Huh? Three different mfgrs in Sweets have systems as low as 1/12. The PEMB types regularly use roof panels at 1/12.
Are you maybe thinking on metal shingle panel roofing?Occupational hazard of my occupation not being around (sorry Bubba)
Sorry, I shopuld have expanded on my post a little further and not just quickly post something.
2/12 is too low for exposed fastener metal roofs. Washers on the fasteners age and become brittle and leak. The panels expand and contract and enlarge the holes and cause further leaks.
There are many manufacturers of hidden fastener panels that work well in low slope i.e. Pre-Eng buidling manufacturers etc.
My experience is also up north in Canada in the ice and snow climates. Low slope would work ok in the drier southern areas.
Ok, just wanted to be sure (inserted that 1/12 pitch tag a few dozen times this year . . . )
in the drier southern areas
We may be southern, but it's not necessarily drier. Average rainfall for my relative longitude in Texas is 36" ±3"; for my county the design 24 hour maximum is 15" of rain. Toss in an average mean relative humidity of 45%, and it's hardly ever "dry" here . . . <g>Occupational hazard of my occupation not being around (sorry Bubba)
I wouldn't worry too much about engineering issues and cold roof since your existing 2:12 gravel roof has already proven itself cpaable of holding all the snow anyway. You'd be much more likely to damage a tar roof shovelling than a metal one.
My preference would be to double strap it with 2x4s and go with standing seam metal (concealed clip fasteners). Use T&G plywood under the double strapping and that glulam structure will hold an entire season's worth of snow. Cold roof means no sliding off, and ice dams won't be an issue because the roofing will be fabricated on site in one continuous run from eave to ridge.
Now shovel that old roof off and go skiing. It's dumping here in southern interior BC, hope you're gettin some of that. Tomorrow gonna be a good powder day.
Wally
I would be very careful about doing a meetal roof in that kind of snow country andf a 2/12 pitch. I would build in redundancy with ice and water shied and cold roof.
A cold roof and metal would be less weight than your current BUR. You would need to study the specs on spans for the particular product to space out the sleepers for tjhe cold roof/fastening schedule.
you can easily do more damage to a metal roof with a snow shovel than to an EPDM roof.
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