Ice dams

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Old 01-23-18, 06:44 AM
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Ice dams

Hello,

Our new house (built 1978) had had some minor ice dams this winter in one section adjacent to the front door and garage area.
Roof with ridge vents and R50 insulation were done in 2009.
Previous homeowner had heated cable running in the gutter and throughout a flat portion of the roof.
Snow seems to accumulate on the flat valley portion (between 2 peaks). Itís also a shaded area because of the peak. The previous homeowner seemed to concentrate the cable in the flat area and had no cables along the bottom edge of the roof.

Iíve combatted the ice damming by using my new roof rake. Fun! After a major snow fall and cold temperature, I notice the ridge vents were covered for at least a week.

Is heat escaping the only real cause of ice dams? Even after a major thaw and 2days of rain, the flat area still has snow.

Should the heat cables be run in the flat area to encourage melting of the snow or should they be used exclusively along the roof edge to prevent freezing.

I can send pics if that helps.
 
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Old 01-23-18, 07:36 AM
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snow is good

In my experience, snow on the roof is a sign of good insulation. If you had spots where heat was leaking out, you would see the bare roof or ice instead. No sign of ice or roofing says the insulation is working. Yes, you still want to keep the snow load light, but everything else sounds pretty good.
 
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Old 01-23-18, 08:55 AM
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Is heat escaping the only real cause of ice dams?

The statement should read, is heat the contributor to ice dams. To that the answer is yes.

Heat causes the show to melt which then runs down to the overhang and gutter which is colder and refreezes.

It's caused by heat loss through the roof and to a less extent the sun.

I have 2 valleys that the snow tends to drift. As long as it's really cold, no issues. But if we get some sunny days I get a little snow melt and ice will start forming.

I find if I can clear 4' of snow removed above the gutter any water that flows will evaporate before it hits the overhang.
 
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Old 01-23-18, 11:58 AM
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Here are pics of the east and west sides....both of snow build up after mild and wet weather. Didnít take a pic of where the dams form. Do you think itís better to keep the heating wires where they are(you should see them in 2 of the pics). Or run them along the roof edge where they typically go?
 
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Old 02-16-18, 12:30 PM
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Here are some more photos of where the dams occurs. From the original photos, the snow melts and runs down to this area of the roof where it builds up. Donít think itís all a result of heat loss. Seems like itís the sun and the amount of snow and poor roof design has all the water from that area going down to the section shown in my new photos.

For next year, should I run leave the cables where they are or put more of them in the area where the dam occurs.
 
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Old 02-16-18, 04:31 PM
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Honestly that doesn't look like an issue, when you have huge icicles hanging off the gutters that is a concern. You have a low spot that collects snow but unlike real ice dams its not backing up under the shingles.

I use a roof rake in my valleys to remove the bulk of show so the sun can do it;s thing!
 
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Old 02-17-18, 03:07 AM
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I did have large icicles hanging from the gutter in the area where the Downspout is located. I started chipping and clearing them off. Yes, the low spot of the roof slopes down, makes a 90 degree turn and comes down the area in the last few pics. Itís there that the build up occurs...Iím assuming just based on the volume of melt from the upper areas being connected treated in one little spot.
 
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Old 02-17-18, 06:15 AM
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I started chipping and clearing them off
Breaking off the ice can cause damage to gutters, downspouts and fascia.

Have you tried a rake vs attempting to heat?

I dont recall the brand but this looks like it. It has wheels that roll on the roof and as you cut into the snow it flows down the fabric. I have 3 areas I hit every time we get deep snow and it takes 20 minutes . Getting the snow out of the valleys eliminates all ice formationl

https://www.doityourself.com/forum/a...1&d=1518876921
 
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Old 02-17-18, 01:23 PM
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I rake what I can in the area in the last 3 pics. The majority of the runoff comes from the area shown in my first set of pics that I canít reach. Iím wondering if I just concentrate the heating cables in the area in the last few pics vs in the area of the first few pics.
 
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Old 06-19-18, 08:21 PM
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Back again. Figured I would try and solve my ice dam issue now since itís summer.
Iíve edited some of the previous pics to show the existing heating cables in red and the flow of water in blue from the valleys in the centre of the roof towards the front of the roof. Hoping to give you a sense of the roof design.

Thereís also a small prow roof section right above where the ice buildup forms and I noticed during a rainstorm that water is coming off the prow and falling onto to the shingles below right where the ice buildup would be.

1. Do the heat cables belong where they are now? Iím wondering if they may be contributing to the advanced melt and causing the dam to be worse
2. Should I concentrate the heat cables in the area of the dam and also run the cable down the downspout?
3. Any other ideas? Should the prow roof have gutters on them?
4. Could I install a gutter in the green area to capture water running from the valley and off the shingles?

The problem exists on the other side of the front door but to a lesser extent. The area Iím mostly talking about is mostly over an up heated garage but the close to the heated entrance foyer. Problem areas circled in yellow.
 
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