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Old 10-16-2013, 04:48 PM   #1
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How much ice shield is recommended


I need a new roof but my house is two stories and I'm not into heights so I'm getting bids for the work. I got two bids that are identical except for ice shield and price. The cheaper roofer shows up a certified installer on GAF site but they only want to do 3 feet of ice shield around gutter edge and chimney and vent pipes. Other company costs more isn't GAF certified but does 6 feet of ice shield. Both would install same ridge venting systems for a house without a soffit. Soffit cannot be added either. Neighbor tried and got turned down by municipality architecture review board for historical significance of house design. House is only from 1946 though. I am in milwaukee area.

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Old 10-16-2013, 05:02 PM   #2
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How much ice shield is recommended


There should be ice and water from the edge of the eaves to two feet horizontally inside the building line (the outside of your wall). So unless you have no or next to no soffit projection 2 rows are required (6')

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Old 10-16-2013, 05:39 PM   #3
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How much ice shield is recommended


I have no soffit. Almost all colonial homes in my area have no soffit and just attach gutters to roof line.
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Old 10-16-2013, 05:39 PM   #4
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How much ice shield is recommended


24" inside the warm wall is the usual minimum standard.
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Old 10-16-2013, 05:46 PM   #5
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How much ice shield is recommended


Okay guess 3 feet is fine then.
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Old 10-16-2013, 06:12 PM   #6
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How much ice shield is recommended


To determine the amount of ice shield you would like one first needs to understand that water entering within the building line doesn't come from the top of an ice layer as depicted in so many web sites but from under the layer of ice. So with than in mind if you have 3 ft. of ice shield water can not enter at the 3 ft. mark or lower, but can enter above that, if and only if the installer gets a PERFECT seal in that 3 ft. distance. The same scenario applies at the 6 ft. measure.

Here is an example of how water enters your walls and it isn't from the big ugly glob of ice that looks as if it will cause the eaves to collapse. Lets say a common freezing rain puts an eighth inch or maybe more of ice on your roof followed by insulating snow of any amount but under certain weather conditions more is worse.

Everything is just fine for awhile because the weather is really cold and you have followed so much advise about insulation amounts, attic sealing and proper venting and in your mind everything will be ok. But with all the preventive measures your structure still looses some heat into the attic. Impossible to prevent that.

Now along with that natural heat loss, as it usually does, the weather at some point changes and the outdoor ambient temperature rises to 33F or more. So now with that excellent venting job we are getting air just above the freezing point to the sheathing underside. Ever wonder what that will do?
As nature would have it it will cause a minute layer of water under the ice layer and those little molecules are just waiting to escape to anywhere that's easy. In this instance they can go under at 3 ft. or 6 ft. because of head pressure from the ridge line. So for ice shield to be effective it must cover the entire roof and have a guarantee from the roofing contractor it will be 100 percent sealed. What are the odds of that guarantee happening. 0 in 10,000,000. I wish you well.
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Old 10-16-2013, 09:54 PM   #7
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How much ice shield is recommended


how far up the ice and water extends varies by region. in canada its required to be up 3` beyond the line of the top plate. some guys still only go with 1 row. we typically ice and water the entire roof though were in renovations and addtions. we put hte ice and water on to keep water out untl the roofer arrives
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Old 10-16-2013, 10:38 PM   #8
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How much ice shield is recommended


In my neck of the woods, first row is required to be Ice & Water Shield. Unless you are in an area of Milwaukee, that you get a lot of Lake effect Icing, first row should be fine. Grace now makes a material, that took the place of Roofing felt, that works just like Ice & Rain Shield, but holds up longer then standard roofing felt.

As for shingles, my roofer went with Elk line of GAF, since they have the tar at the bottom front, vs. more towards the top half of the shingle. Makes it harder for the shingle to be lifted up during a wind event.
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Old 10-17-2013, 03:40 AM   #9
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How much ice shield is recommended


one row 3 feet will fly. However new roofing practices say 6 feet. It depends on where your interior wall starts.(new roofing practices) I like certainteed landmark shingles. However i'm not going to bad mouth gaf timberlines. Lot of roofers go with timberlines you pretty much have to request a landmark.

Finally as gregzoll says grace does have some slick underlayment. Certainteed roofers select is a synthetic underlayment. I also like titanium udl 30

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Old 10-17-2013, 08:40 AM   #10
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How much ice shield is recommended


It is hard to believe that anyone would build a house without soffits in Wisconsin, because good air flow under the roof deck is the real secret to avoiding ice dams.
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Old 10-17-2013, 10:01 AM   #11
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How much ice shield is recommended


Yeah, I don't know if they thought about that in 1946 when it was built. I live in a suburb of Milwaukee that is very strict on architectural changes to homes so I cannot modify the roof. I live may 7 blocks from the lake but ice dams has not been an issue in my two winters of owning the house.
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Old 10-17-2013, 10:25 AM   #12
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How much ice shield is recommended


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Originally Posted by bryanp22 View Post
Yeah, I don't know if they thought about that in 1946 when it was built. I live in a suburb of Milwaukee that is very strict on architectural changes to homes so I cannot modify the roof. I live may 7 blocks from the lake but ice dams has not been an issue in my two winters of owning the house.
Then maybe you don't want to change what has been working? Ice dams material will create a vapor retarder, or pretty close to a vapor barrier.
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Old 10-17-2013, 03:33 PM   #13
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How much ice shield is recommended


With 30#/ft2 snow load per location and R-20-30 attic insulation, no ventilation and attic air sealed from below, use 3' of I&W, if any-IMO.

http://publicecodes.cyberregs.com/ic...?bu2=undefined

Chart #2; http://www.google.com/url?sa=t&rct=j...tnueeZLlmJN7qw

And Fig.B; http://www.brainerdhomeinspection.com/roofve~1.pdf

Code min. ceiling insulation is higher now; R-49; http://energycode.pnl.gov/EnergyCode...tate=Wisconsin

http://www.google.com/url?sa=t&sourc...wWATQw&cad=rja

Air seal the crawl/basement against stack effect; http://www.wag-aic.org/1999/WAG_99_baker.pdf

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Last edited by Gary in WA; 10-17-2013 at 03:41 PM.
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Old 10-17-2013, 10:14 PM   #14
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How much ice shield is recommended


I/W is a vapor retarder but the roof isn't drying through the felt and plywood either way.

If the attic is air sealed and insulated, the necessities for venting are a bit reduced but like Jagans said, a well vented roof is a happy roof.

There are alternative venting options that will work like soffits do.
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Old 10-18-2013, 06:51 PM   #15
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How much ice shield is recommended


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Originally Posted by Windows on Wash View Post
I/W is a vapor retarder but the roof isn't drying through the felt and plywood either way.

If the attic is air sealed and insulated, the necessities for venting are a bit reduced but like Jagans said, a well vented roof is a happy roof.

There are alternative venting options that will work like soffits do.
Most-if not all- I&W are true vapor barriers with a perm rating of only 0.05perm, close to same as 6mill poly- a Class 1 vapor barrier; http://www.google.com/url?sa=t&rct=j...IU5FiTymBYhcSA Why would one use a vapor retarder when you want/need a waterproof vapor barrier under the ice dam...

Roof can dry through felt paper (with 6/31 perms) or plywood (0.75/3.5 perms); http://www.buildingscience.com/docum...roperty-table/

This chart brings it into perspective, compare the numbers (already listed above) for felt/plywood on it; Page 3;http://www.rci-online.org/interface/2010-04-gatland.pdf

I think the OP will be fine (no ice dams/moisture signs) without attic ventilation as the house has been since built... Eric, what is your opinion after reading info in the link from above with the Charts 2, 3?; http://www.google.com/url?sa=t&rct=j...tnueeZLlmJN7qw

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