Effectiveness if ice shield in cold winters

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  #1  
Old 01-21-09, 09:12 AM
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Effectiveness if ice shield in cold winters

I have a low slope shed roof that had leaked anytime ice dams built up at the eaves. Two years ago I had the roof replaced with ice shield installed over the entire pitch. Two winters passed without any leaks but this year the leak is back. The installer told me that ice shield helps but wonít entirely waterproof a roof if large dams build up. Itís been a cold, snowy winter this year in Michigan and the ice dams were about 3Ē thick at the roof edge. I used ice melter to remove the dams and once the weather warms up Iíll reinstall my heat wires, but Iím wondering whether the installer is being honest with me. I thought the whole idea behind the ice shield membrane was to catch that water that had backed up behind the dams.

Does the ice shield membrane loose itís effectiveness when the temp is in single digits?

Thanx - Rick from The Great White North
 
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Old 01-21-09, 01:25 PM
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No, the effectiveness of the ice shield is not diminished by low temperature.

It could be installed wrong.

Or it may be the wrong situation to install it at all.
 
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Old 01-23-09, 05:10 AM
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You have the entire roof deck covered with Ice and Water Shield. That's great, good idea. You don't say where the leaks are in the roof. If your leaks are at the eave where the gutter is, what' happening is the water is getting past the facia board and into the soffit and then into your house. To really make this stuff work properly, it needs to be run behind the facia and up onto the roof deck continuously. No one does this because it' too much work I guess. The gutter and facia have to be removed and reinstalled after the membrane is in place. If your leaks are out in the center of the roof, somebody screwed something up. Ice damming is caused by inadequate insulation and ventilation. You may want to pursue that also.
 
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Old 01-26-09, 01:00 AM
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no,your detail at the gutter is lacking.you should have a metal eave flashing behind the gutter,so water doesn`t back up behind the gutter,and over the fascia [IMG][/IMG]
and then secure the gutter on top of the flashing,I also like to seal the back of the gutter to the 3x3 with Geocell tri-polymer sealant-I`m in Rockland county,deal with Ice dams all the time
[IMG][/IMG]
 
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Old 01-26-09, 10:28 AM
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There were ice dams at the edge of the roof and the leak was directly under that spot.

I had ventilated the soffit with those 3" round vents (one per rafter bay) and had ridge vents installed with the new roof. I also closed off the gable vents and instaled 6" more insulation in the attic.

Fortunately, this is a short length of roofline so this summer I'm going to pull the soffit and facia and get serious about venting and waterproofing that area. I particularly like the eave flashing idea.
 
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Old 01-28-09, 12:21 AM
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3" soffit vents aren`t enough---the eave flashing system I use has survived harsh NY winters for about 20 years now--MOST ice + water backups occur when the water backs over the gutter into the soffit,and then down your bearing walls
 
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Old 01-28-09, 05:38 AM
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What's the vapor retarder and insulation situation in the attic of the shed? Warm, humid air from below rises. All gaps to attic space should be sealed. Vapor retarder installed. If batt insulation was used, the face side (vapor retarder) faces down to area below. You did not indicate if the shed is heated. Attic area needs recommended ventilation for size of space and recommended insulation for your area.

When warm, humid air rises through the attic space and/or roof, it melts the snow which runs into the gutters where it freezes and results in ice dams. Gutters full of frozen ice can not accommodate the continued snow melt. It runs backward into fascia and can enter walls, and it runs forward and drips over to often form big, fat icicles.
 
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