Both shingle manuf and roofing tile manuf list 3:12 as the minimum slope for their products. Every use either product on that slope? Special measures taken?
Location: Reno
We can always do a metal roof, where that slope isn’t a problem. But if client desires shingle/tile, I’m trying to get smarter on what to expect and how to avoid problems.
Replies
You can use Ice & Water Shield as the underlayment adhered to the roof deck (use WB Primer to get a super bond) if the building inspector will accept it.
Most 3 tab shingles give 4/12 as the minimum slope with standard underlayment. This can be decreased to 3/12 with double #30 felt half lapped or complete I&WS coverage.
Most dimensionals are 3/12 minimum with standard underlayment and go down to 2/12 with the same treatment as above.
I'm working on a Vandehey Raleigh tile job and they give 3/12 as minimum slope in "no snow" country and 4/12 in snow country.
My tile experience tells me to I&WS the entire deck no matter what the slope is.
We were doing a 2/12 roof with dimensionals today. I've done it since the manufacturers have signed off on it with no problems.
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Where in Reno? In-laws are a bit south, on the Mt. Rose highway. They've seen their concrete tile roof rolling like waves of grain in the 100mph bursts they get up there occasionally.
Down in the valley snow isn't usually much of an issue, but they can get it (airport shut down a few years ago for a couple of days it was so thick - so you have to plan for it).
If it was my house I wouldn't go that shallow of a slope.
It's only a narrow section of roof, a space along the front of the house maybe 10' deep, a glorified covered porch. That affect your perspective at all? Loads will be handled properly by engineer. Want to make sure we can shed water.
That is a placement where you have to think about excessive drifting of snow sometimes. Also, porch roof can be colder and have ice dams from melt off on upper roof draining to it.
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Shingle and tile are two totally different approaches.
Does Reno get much snow build up? If so, you need plenty of I&W or double underlayment 30#
A tile roof sheds *most* of the water.
A lot finds a way past the tiles, especially in wind driven conditions and when there is snow and ice.
So the underlayment is critical. The old standard was two plies of 30# felt, all sealed snug before starting the tile work. The actual waterproofing was the underlay and the tile kept the sun off so it didn't dry out.
Now, full I$W for tile underlay is common, especially at that pitch.
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I used inexpensive 3-tabs on my shop at closer to 2/12, and have had ZERO problems in 7 years. Suspended ceiling below is fine.
No special techniques; don't even get the leaves off but once a year maybe.
Atlanta area, but no wind.
Forrest
Shingles on low slopes are asking for trouble in snow areas. You're lucky your in Atlanta because you'd have leaked on the first snow. Years ago, I put a shed addition on for a plumber with 2/12 or 3/12. He didn't want roll roofing and insisted that I lay 3 tabs. I was working by the hour for a fellow trademan so I told him I would but I wouldn't warrant it. Long story short; it snowed a wet snow hat day and the meltoff the next day caused a leak. It's the ice dam syndrome. We pulled all the shingles up and he paid us to lay roll roofing the next day. Nowadays, I'd lay solid Ice and Water Shield. Since I've come to Texas, I've discovered that the felt crowd is right. In wind driven areas, the felt actually does something! Okay...I said it: I was wrong! For those in the know: if Ice and Water is too pricey as an underlayment, and felt too risky, is there an inbetween product? I think I'd like to use it on some upcomiing projects here in Austin. If not, Ice and WAter underlayment will be the norm for me. I don't want any callbacks.jimfka (formerly known as) blue
Couple weeks back somebody came up with a said same quality product as Grace I&W Sheild at a much lesser cost
and was going to get back with more data but I haven't seen the thread show up.
No snow either
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<No snow either>
It's true - been lucky with it, I know. It's one of those temporaried-up deals that just has lasted! It's had rotting leaves on it literally ankle deep for months, though.
Forrest