Ice dams

JMynes · Feb 9, 2011

JB4310 said:
Notice how the ice dam has a level top, that gives you a relativly safe place to walk on a pitched slippery/icy roof. If you could call a 4-8 inch wide ice plank at the edge of the roof "safe"
JB.

I strongly disagree. If you're walking on that "safe place" and it cracks loose, you're going for a big ride! Seen it happen, don't want any part of that.

Jay4200 · Feb 9, 2011

JB4310 said:
I would say 90% of the houses around here have ice dams, new, old ventilated, insulated doesn't really matter this year. Not everyone has leaks but everyone has ice as thick as a street curb. It's almost impossible to remove without some invassive approach.

Sure it matters. I don't have even one teeny bit of ice on my roof - just 3 feet of snow. The only reason for ice on a roof is piss-poor construction.

I spent a little money and a bunch of time fixing insulation and increasing my venting through the years. There is nothing special about my house like super-insulation or anything, just your normal R30 ceiling and R11 walls - the big difference is that I have the insulation CORRECTLY installed (because I did it, not some retarded incompetent contractor) and my roof is well vented, with a wide-open soffit and plastic baffled ridge vent (also installed by me).

JayC

dave1949 · Feb 9, 2011

Something to think about, a well ventilated attic space will warm the underside of a roof on days when the temperature gets above freezing. That can cause a little melting under the snow on the roof and that dribbles down and freezes on the exposed eave edges as the temperature drops in the late afternoon. Everyday this happens, which is many of them in the northeast, a little more dribbles down and freezes, building the ice dam. How much insulation and air sealing you have in your ceiling has nothing to do with this process since its the outside air temperature doing the melting. In an average house, there is no doubt some heat leakage from the living space into he attic space that helps the process along too.

I wonder how those newer 'encapsulated attic space' methods work for ice dams? Could be an improvement.
Dave.

dave1949 · Feb 9, 2011

Bird said:
About 30 years ago was the one and only time I saw that happen in Dallas. We'd had quite an ice storm and the next door neighbor called about 2 a.m. to tell me he got up and went to the bathroom and water was running out around a light fixture, so he wanted to borrow my ladder to get up in the attic to see where it was coming from. I felt sorry for him, but was thinking I was glad it wasn't me as I walked barefoot in the my pajamas through the dark house to go open the garage door so he could get the ladder. And as I walked through the kitchen, I found I was walking in water and had water pouring out around a kitchen light fixture. I'd never heard of ice dams before but learned that quite a few people in the Dallas area learned about them that day.

That's just too funny, Bird. As I was cleaning snow off my roof the other day, I began to wonder if I could still do it when I'm 70 years old. A person has a lot of time to think when clearing roof snow. It's extremely boring for the most part, with a few exciting sled rides down the roof in between long bouts of repetitive actions. :laughing: My eaves are only 4' off the ground, so I'm in no danger.
Dave.

JB4310 · Feb 9, 2011

JMynes said:
I strongly disagree. If you're walking on that "safe place" and it cracks loose, you're going for a big ride! Seen it happen, don't want any part of that.

I agree, though this ice you can beat on with a sledge hammer and just get chips.

That's why I said relatively safe, The idea of walking on ice at the edge of a roof could not really be called safe by any stretch. It's the way that it is so level that makes it even posible to do the roof clearing from the roof as opposed to from a ladder, which would be so much harder. I've only "walked the plank" on 1 storey homes where the fall with all the snow on the ground would be only 6 feet. I know that's kinda twisted thinking, but it's a managed risk I guess. 2 storey houses, one guy at ridge holds guy at eave with rope.

Jay4200 said:
Sure it matters. I don't have even one teeny bit of ice on my roof - just 3 feet of snow. The only reason for ice on a roof is piss-poor construction.

I spent a little money and a bunch of time fixing insulation and increasing my venting through the years. There is nothing special about my house like super-insulation or anything, just your normal R30 ceiling and R11 walls - the big difference is that I have the insulation CORRECTLY installed (because I did it, not some retarded incompetent contractor) and my roof is well vented, with a wide-open soffit and plastic baffled ridge vent (also installed by me).

JayC

I wont argue with you, I've learned alot this year about the insulation/ventalation factor, but like I said this year it doesn't seem to matter, almost every house old and new had heavy ice dams for the last 3-4 weeks. Maybe partly due to the effects Dave described.

We have alot of older housing stock around here, not poorly constructed by any means but not as climate controlled as the newer homes standards.
My own home which is 75 years old is very well built, but has only a couple of inches of overhang so no way to install soffit venting.

You being further north may have colder constant temps, conditions around here this year were just ripe for ice dams.

JB.

JB4310 · Feb 9, 2011

dave1949 said:
My eaves are only 4' off the ground, so I'm in no danger.
Dave.

I worked on one porch yesterday where I was able to just step (short 2 foot hop) off the roof onto the pile we made

Calls slowed today, phone was ringing off the hook for the last 2 weeks with all the media reports.

JB.

dave1949 · Feb 10, 2011

JB4310 said:
I worked on one porch yesterday where I was able to just step (short 2 foot hop) off the roof onto the pile we made

Calls slowed today, phone was ringing off the hook for the last 2 weeks with all the media reports.

JB.

Maybe you'll get a little breather.

A big dairy barn went down in Clinton, ME yesterday. They lost four cows but able to get most out. From the news camera reports, it had a fair amount of snow on the roof, but it didn't look all that heavy. Just shows how deceiving it can be.

I'm thinking wind and snow loads on a roof are additive. Could be situations where the snow load is within design, along comes a windy day and adds to the load causing failure.

Dave.

JB4310 · Feb 10, 2011

dave1949 said:
Maybe you'll get a little breather.

I'm thinking wind and snow loads on a roof are additive. Could be situations where the snow load is within design, along comes a windy day and adds to the load causing failure.

Dave.

We definitely got a breather and a chance to catch up almost a week now.
Thank God because it was really starting to get stressfull.

I was thinking the exact same thing about the wind, not something you might think would affect roof load normally.
But with all the cave ins you know there are many that are just a trigger pull from going down, that's pretty scary to ponder, who's under a roof that is 1 pound away from collapse.

The collapses have ceased here in the last 2 days, but there was one auto body shop that came down Tuesday after just an inch of additional snow, and like the fire marshal said on the news, "that one inch was the straw that broke the camels back"

Would think a strong wind could create enough of a dynamic as an inch of snow, not as much to a flat roof of course, but probably still some extra load.

JB.

WBWI · Feb 10, 2011

My house it 3 years old and well constructed. We built in the woods so we used leaf guards on all the gutters. My ice dam problem seems to happen with the bathroom fan vents melt surrounding snow. The water flows to the gutters but once it hits the metal gutter covers it refreezes and creates the dams. I don't have a good solution for the problem yet.