# ice and water code



## tnt specialty (Apr 19, 2007)

ED; Read it again. 

As I recall, the pitch determines the distance inside the wall I believe.


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## jmorgan (Jan 31, 2004)

It depends on which code your juristiction is using...IRC, IBC or '97 UBC. 97UBC is chart 15b or c. GIWS 24" inside of warm wall.
IRC is 12" inside warm wall for asphalt shingles and 24" inside warm wall for metal, slate, tile, etc
Some juristictions have special rules...for example, ski area towns regularly increase the amount of protection.
Most IWS products have ICC-ES reports that allow one layer to replace 2, mopped, ply flets. This is where full coverage GIWS is used on low slopes.
Jim


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## theroofinggod (Jun 28, 2007)

ice dams are formed from escaped heat melting the bottom layer of snow,it runs down and freezes at the unheated overhang area,repeated melting creates water behind the ice damwhich pushes under the shingles when it refreezes--you don`t get the same thing from the sun melting the top of the snow,therefore no heated structure,no problem,usually a backflashing/dripedge is enough to handle that situation-not a wive`s tale-IMO


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## MJW (Jan 27, 2006)

theroofinggod said:


> ice dams are formed from escaped heat melting the bottom layer of snow,it runs down and freezes at the unheated overhang area,repeated melting creates water behind the ice damwhich pushes under the shingles when it refreezes--you don`t get the same thing from the sun melting the top of the snow,therefore no heated structure,no problem,usually a backflashing/dripedge is enough to handle that situation-not a wive`s tale-IMO


Yes, that's true on older houses that lose alot of heat and have no ventilation at the top plate because of the hand framed rafters and birds mouth. Newer houses with engineered rafters and good ventlation don't have that problem.
the problem on the newer houses is sun melt then ice forms and it creates almost like a glacier. It moves up the roof and under the shingles if it is there long enough. It re-freezes because it is under the snow and protected from the sun. If you have done any snow removal you will see this. And yes, you do get the same effect from snow melt from the sun.


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## skylands (Dec 10, 2005)

I'm with Roofer Jim.

On a 60 foot roof, it's only an extra cost of a hundred bucks to do 6 feet. Anything under a 5 pitch or Valleys, sky lights, dormers and crickets all get the full treatment of I&W. Cheap insurance.


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## theroofinggod (Jun 28, 2007)

no where near as severe though-MJW---This also depends on your respective climate


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## tekwrytr (Sep 11, 2007)

MJW said:


> Are you licensed? If so, this is brought up every year in every class I have been to.
> The new code says to do what is on the product package. The inspector cannot enforce anything more than what the code says, but most of the time it is easier to do what they say and they know that. Some packages say two rows, some say 24" past the plate line. On a porch there is no plate line for the interior wall so yes it is all supposed to be ice shield. Is it needed????Probably not, depending on which way it faces and how much rain/ice/snow is coming off the top roof on it. This is why I say your roof is only as good as the products you have and the roofer's knowledge. Anyone can do the codes and get by, but a good roof can be a little more thinking than that.
> By the way, the code says ALL roofs need I&W. Also the department of labor says All roofers are to be licensed with the state.


Question--does the "All roofers" apply only to residential, or are you saying that commercial roofers also require state licenses in MN? My understanding is that the licensing requirements only apply up to 4 residential units (fourplexes or less), and don't apply at all to commercial or industrial projects.
tekwrytr


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## MJW (Jan 27, 2006)

If it's commercial then you don't have to abide by residential building codes. You will have to ask the commercial inspector. No, I don't believe there is a license for commercial roofers.


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