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WILL1E
Moderator
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# Posted: 17 Sep 2021 11:15am
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What have you used, why did you choose it and what's been your experience with what you chose?
Doing a metal roof on our 32' long cabin and debating between traditional 30# felt and the newer synthetic stuff. Ill be doing a cold roof with 1/2" plywood for the sheathing. Cost seems to be near identical between the felt and synthetic.
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ICC
Member
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# Posted: 17 Sep 2021 12:26pm
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#30 felt can easily be left exposed a couple of weeks at this time of year. But that depends on how well the edges are nailed to keep the winds from lifting and tearing it (using the plastic washer roofing nails). I would sometimes secure the edges with scrap 1x2 or whatever was handy and leave it for a month when necessary.
Or buy a premium synthetic which comes in wider rolls and cuts down on the number of seams/edges. Most can be left exposed 90 days and still be warranteed.
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thes10kid
Member
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# Posted: 17 Sep 2021 12:27pm
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Will1e,
I do estimation for a commercial roofing company in Southern Vermont installing mostly metal standing seam roofing. We use two products exclusively, and (knock on wood) have not had any call-backs in 8 years. We use 3' of Grace Ice and Water shield on the lower eaves of the roof to mediate ice-dams, and GAF Deck Armor on the remainder. Both great products. I have linked to Home Depot for the products just to make things a bit easier.
https://www.homedepot.com/p/GAF-Deck-Armor-1000-sq-ft-Premium-Breathable-Synthetic-Ro ofing-Underlayment-Roll-0907/202531707
https://www.homedepot.com/p/GCP-Applied-Technologies-Grace-Ice-and-Water-Shield-36-in -x-75-ft-Roll-Self-Adhered-Roofing-Underlayment-225-sq-ft-5003002/202088840
I hope this is helpful,
Adam
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WILL1E
Moderator
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# Posted: 17 Sep 2021 12:51pm
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Are ice dams a concern even on steep pitch roofs and/or roofs w/o gutters?
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NorthRick
Member
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# Posted: 17 Sep 2021 02:04pm
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Quoting: WILL1E Are ice dams a concern even on steep pitch roofs and/or roofs w/o gutters?
Much less of a concern but it is just good practice to put water and ice shield around the edges of the roof. After that I've just gone with 30# felt with no problems.
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ICC
Member
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# Posted: 17 Sep 2021 02:23pm - Edited by: ICC
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Quoting: WILL1E Are ice dams a concern even on steep pitch roofs and/or roofs w/o gutters?
Ice dams are mostly a problem when insulation and/or air sealing is insufficient. It is better to use the Grace product (they have been around for a long time and know what they are doing) and head off the issue. Adding it later after leaks inside appear is not possible without removing the roofing. It is a 2+ person installation job.
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travellerw
Member
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# Posted: 17 Sep 2021 02:48pm
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Not sure what the situation is like down there, but up here delivery times are long. Most suppliers are minimum 3 weeks and some are 4 weeks.
I would call around..
Also, they will suggest the underlayment they recommend. I would stick with that!
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WILL1E
Moderator
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# Posted: 17 Sep 2021 03:13pm
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Pro-rib manufacturer just confirmed 30# and ice guard if code requires it.
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Brettny
Member
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# Posted: 17 Sep 2021 03:19pm
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I plan to use something like this under my metal roof.
https://www.amazon.com/gp/product/B01M0QI05K/ref=ox_sc_saved_title_4?smid=A274P7ERGX9 CS8&psc=1
Its rated for metal roofs. I dont believe tar paper is. It's also about half the price of the HD link. They do make different grades of thus tyvex brand stuff too.
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snobdds
Member
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# Posted: 17 Sep 2021 08:20pm - Edited by: snobdds
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Quoting: ICC Ice dams are mostly a problem when insulation and/or air sealing is insufficient.
Yep.
Hot air leaks, heats underside of roof, melt runs down and freezes on soffit overhang. Ice dam.
It's simple, don't ever let the roof get warm.
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ICC
Member
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# Posted: 17 Sep 2021 09:49pm
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You may be pushing your time vs weather window on this job. I believe the Grace Ice & Water Shield installation info states that the air, the roof deck, and the ice & water shield membrane all have to be installed at 40 F or higher. It may not adhere to the roof deck material if too cold. And if it doesn't stick well you have wasted some money.
I believe Grace states a 120 day exposure limit.
I have left a cabin sit overwinter (November to April I think it was) with strapped down #30 felt. We replaced the roll out over the peak IIRC. The rest was okay.
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NorthRick
Member
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# Posted: 18 Sep 2021 12:44pm
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Quoting: ICC You may be pushing your time vs weather window on this job. I believe the Grace Ice & Water Shield installation info states that the air, the roof deck, and the ice & water shield membrane all have to be installed at 40 F or higher. It may not adhere to the roof deck material if too cold. And if it doesn't stick well you have wasted some money.
Use some roofing nails to hold it in place until it warms enough to stick. It's actually easier to install in the cold as you can get a "do over" if it is misaligned.
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